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University of the Witwatersrand, Johannesburg
SCHONLAND RESEARCH CENTRE FOR NUCLEAR SCIENCES
Annual Report
1998-9
Diamond Bending Device (see page 41)
Introduction..........................................................................................................................3
Applied and Environmental Physics Research Group.........................................................4
Ion Implantation and Surface Studies Research Programme.............................................19
Nuclear Physics Programme..............................................................................................28
Wits-Northern Accelerator Research Centre ...................................................................32
Health Physics Service ......................................................................................................69
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Introduction
This Report covers the first full year (1998) of the implementation of the new Schonland proposals, plus part of 1999, being based on the reports prepared by the various Groups for their Annual GeneralMeetings at different times in 1999. In accordance with the Physics Department's plan, the Schonland Research Centre for Nuclear Sciences is now in effect a federation of four Research Programmes, each with its own Group Leader, sharing a common support infrastructure. In addition the University's Health Physics Service has its home at the Schonland. Some of the Groups are subdivided internally along the lines of individual research interests, as will become apparent in this Report.
Matters of common interest are overseen by a Schonland Co-ordinating Committee with a rotating(2-year) chairmanship, chosen from the Group Leaders. The Chairman for most of the period under review was Prof. Vladimir Hnizdo, but since his resignation in the middle of 1999 to take up a post in America, Prof. Trevor Derry has taken over the job.
The four recognized Research Entities are:
- Applied and Environmental Physics Research Programme (Prof. J.I.W. Watterson);- Ion Implantation and Surface Studies Research Programme (Prof. T.E. Derry);- Nuclear Physics Research Programme (Prof. V. Hnizdo then Dr. J.M. Carter);- Wits Northern Accelerator Centre (Dr. S.H. Connell).
To these must be added the Health Physics Service (Dr. T.L. Nam).
The current membership of the Schonland Co-ordinating Committee is:Prof. T.E. Derry (chair), Dr. S.H. Connell (deputy chair), Prof. J.I.W. Watterson, Dr. J.M. Carter, Mr. A.H. Andeweg (Technical rep.), Mr. D.B. Rebuli (Postgraduate rep.), Prof. B.J. Cole (Head of Physics Dept.) and Prof. W.U. Reimold (Geology Dept.); other representatives attend meetings from time to time.
The Schonland Research Centre's mission is to pursue a vigorous programme of both pure and applied nuclear research for the African context, including overseas collaborations where appropriate, integrated with the training of our higher degree students.
The University's recognition of separate Research Entities under the Schonland umbrella has been very successful. Attention and effort has now been freed for the business of research and teaching, and several major projects have blossomed, as detailed in this Report. Notable has been the implementation under International Atomic Energy Agency auspices of an annual five-month Radiation Protection Course serving the whole of Africa, which necessitated major structural changes to the Schonland buildings to accommodate some 20 students plus donated equipment.
Trevor Derry.February 2000
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Applied and Environmental Physics Research Group
August 1999
J.I.W. Wattersonand
B. Th. Verhagen
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1. Introduction
The philosophy of this group is to carry out intrinsically interesting research in physics in an academic way and apply it to areas that are of interest in and practical importance to a developing country like South Africa. It is a fact that much of the research, particularly in physics, in most developing countries is not of direct relevance to that country. It does contribute to the development of humankind and it is certainly of cultural importance, but it does not contribute to the economic, environmental or social well-being of that particular country.
Jeffrey Sachs, Professor of International Trade at Harvard and Director for the Centre of International Development has made this point particularly well in a recent article in the Economist. He points out that the vast majority of scientific research is undertaken in areas that are mostly only of direct relevance to developed economies. He presents a chart which shows the overwhelming dominance of the rich countries in publications (90% of the total) and patents (95% of the total). He also points out that rich countries even benefit from the scientific talent of the poor countries and that many of the scientific and technological breakthroughs are made by poor-country scientists working on rich-country problems in rich-country laboratories. This could be further extended by observing that t even research in the laboratories and universities of the developing countries uses scarce local human resources and equipment to contribute to the solution of problems mainly of relevance to rich country science and hence to the economies of the richer nations.
Two South African examples that spring to mind are those of computed tomography discovered by Cormack in South Africa in the 1960’s and radical heart surgery associated with the name of Chris Barnard. In spite of the fact that these originated in this country, today CT scanners are all manufactured in the United States or Europe and artificial heart valves are manufactured in the United States and sold throughout the world. The economic benefits of these world class advances have been negligible in the country of their origin.
The Applied Physics Research Group pursues lines of research established by us in the Schonland Centre over many years, applying the techniques of Physics to the understanding of problems of economic and social importance in the context of Africa. This programme has three main themes: the application of isotope measurements in the understanding of water systems, the application of nuclear-based methods to mining and the understanding and measurement of radiation in the environment. All of these fields include elements of pure science and academic research as well as the development of direct economic and social benefits.
The application of isotope measurements in the understanding of geohydrology has been pursued at the Schonland, since its founding as the Nuclear Physics Research Unit in 1960, in the Environmental Isotope Research Group. Under the leadership of Prof B. Th Verhagen, the Environmental Isotopes Laboratory has been established as probably the foremost laboratory in Africa for the measurement of light isotopes in this field.
The development of nuclear techniques in mining had its origin in the National Institute for Metallurgy’s Activation Analysis Research Group, which was later broadened to include the development of techniques for on-line measurement.
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It is important to realise that these activities, together with air pollution studies and many programmes on diamond physics, and geology always were the core research programme of the Schonland Centre. Other activities such as the neutrino collaboration with Frederick Reines of Case Western University in the 1970’s and various experiments on Nuclear Physics were peripheral.
There are thus three main programmes in the Group, the Environmental Isotope Programme, the Applied Nuclear Physics Programme and the Programme on Radiation in the Environment.
2. Environmental Isotopes Programme
2.1. Historical
The Group had its beginnings in the late 50's as the tritium laboratory, the initiative in the Department of Physics actually pre-dating the establishment of the Nuclear Physics Research Unit, which was to be renamed the Schonland Research Centre (SRC) in the mid-eighties.
The initial aim was the development of methods to enrich environmental tritium. The practical applications of tritium to hydrological problems were made in the late 60's. In the early seventies, the requirement of studying deep ground water with high residence times in the Kalahari prompted the development of radiocarbon analysis. A Water Research Commission contract to study ground water in the northern Cape and Sishen mine allowed for the expansion to stable isotope analysis which added mass spectrometry to the facility, re-named the Environmental Isotope Laboratory, in the mid-seventies.
Numerous studies, mainly of ground water systems but also of other environmental concerns followed, using the largely home-built low level counting facilities. During this period, the Environmental Isotope Group (EIG) became internationally acknowledged, generating many cooperative studies and research contracts. These were conducted with this and other universities, local and international research bodies, government agencies, and the private sector. The Group Leader spent several extended periods abroad being invited to participate in projects in this context.
By the mid-nineties, the Group became more actively engaged with the International Atomic Energy Agency (IAEA) in cooperative research programmes (CRP's) and a Regional Model Project for northern Africa, involving seven countries. The Group rendered expert services to this project in the course of which a similar endeavour for southern and eastern Africa was proposed. This new model project, which had its inception on 1 January 1999, is centered on the EIG as a regional facility responsible for training, scientific input and analytical services. To facilitate the latter, the EIG stands to receive an infusion of state of the art analytical equipment for a total of some R 2 million from the IAEA.
With the re-structuring of the SRC in 1997, the EIG became part of the Applied and Environmental Physics Group (AEPG).
The EIG is at present largely self-supporting and is led by Prof B Th Verhagen, retired in 1997, at present Honorary Research Fellow. Active steps are being taken towards leadership succession for the EIG.
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2.2. Some past achievements
Research at the EIG has revolutionised the hydrology of the Kalahari and other arid and semi-arid environments. This work demonstrated for the time that ground water renewal is an ongoing process in such environments and that resources are not "fossil", or the remnants of earlier "pluvial" periods as believed previously.
The most rewarding of these studies has been producing a conceptual model for the aquifer feeding the northern wellfield of Jwaneng diamond mine in SE Botswana. This has led to an understanding of previously puzzling aspects of the well field's performance; estimates of recharge, later confirmed by water balance studies and information on the potential vulnerability of the system to pollution with changing land use.
The Group has been invited by governments and the private sector to participate in numerous major ground water development projects with considerable success in contributing to conceptual and numerical modelling and thus to the overall resource assessment. This framework of operation could be recommended to the IAEA in their endeavours to propagate the technique especially in developing states.
The final report on a Water Research Commission project and subsequent publication (Verhagen et al. 1999) showed for the time that estimates of ground water recharge in several studies based on isotope "snapshot" data could be corroborated by independent methods which required sometimes many years of observations.
The Group's work on ground water pollution using a wide spectrum of environmental isotopic tracers has been ground-breaking. In various studies using stable isotopes of water and of nitrogen, sources of pollution could unequivocally be established. The Group discovered the distinct isotopic signal on Gauteng mains water as a means of tracing such water in the environment; discovered artificial tritium in landfill leachate as a means of tracing such leachate in the environment; produced the concept of incipient pollution - at concentrations which may not yet be chemically evident but can be identified by their isotopic association.
Using stable isotopes and tritium the Group developed an approach to urban hydrology almost unique to South Africa: using the numerous private boreholes as sampling points for pin-pointing leakages. In the process, interesting small-scale features of ground water recharge were discovered.
The Group contributed to a number of studies by other Departments within this university, notably Geology, Archaeology and Botany as well as at other universities. The Group leader made a major contribution to a wide ranging set of isotope hydrology investigations in the arid zone undertaken by the Federal Geoscience Institute, Hanover, FRG.
2.3. Aims and nature of the EIG
The aims of the EIG are the application of both radioactive and stable isotopes of mainly the light elements (H,C,N,O,S) to the study of processes in the environment. The fields of mostly interdisciplinary research have been hydrology, archaeology, geology, and the life sciences.
The staff of the Group at present consists of the Leader, Prof B Th Verhagen, Mr M J Butler, Research Officer, and two laboratory technicians, Messrs O H T Malinga and B Kumalo.
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Its analytical facilities consist of the following:
* two isotope ratio mass spectrometers (IRMS), one purchased in 1975, the second of about the same vintage, recently donated by the CSIRO in Australia. These are amongst the very few of these instruments world-wide still being kept operational
* two state of the art low level liquid scintillation spectrometers, the purchased from EIG funds with supplementation by the University three years ago; the second was commissioned two weeks ago and is part of the upgrading package financed by the IAEA under the regional model project. The home-built gas counting system was scrapped recently.
* various vacuum lines for sample preparation and handling and general laboratory facilities
Tenders have recently been called by the IAEA for a state of the art mass spectrometer, which is expected to be delivered and installed within the next few months.
2.4. Summary of activities during 1998-99
2.4.1. Activities: 1998
B Th Verhagen travels on expert missions to Uganda and Ethiopia to assist counterparts in IAEA projects to complete their final reports (January). Further investigation with Dr C J Barnes of Australia of the Lake Beseka problem in Ethiopia (January/February)
B Th Verhagen presents invited paper at ICARID international conference in Mumbai, India (February).
The EIG hosts a planning meeting on the project Sustainable Water Resources in Johannesburg attended by representatives of seven southern and eastern African countries. The EIG obtains unanimous support for being appointed Regional Centre for this project (March).
B Th Verhagen presents paper at the International Conference on the Role of a National Geological Survey in Sustainable Development, Gaborone, Botswana (May)
B Th Verhagen presents paper at Geocongress, Pretoria (July)
B Th Verhagen initiates Taaibosch Fault project, South Africa's contribution to the regional model project Sustainable Groundwater Resources (October)
M J Butler attends a research ordination meeting in Sfax, Tunisia on the CRP on Anthropogenic Influences on Groundwater Renewal and presents the Wits progress report (November).
B Th Verhagen travels to Madagascar on an expert mission under the project Sustainable Water Resources (November)
O H T Malinga and J A Geyer of the EIG attend a training course on laboratory techniques in Vienna (November)
Scientific visit to EIG by Messrs Dribidu and J Karundu, Entebbe, Uganda (November)
Delivery of second-hand mass spectrometer donated by CSIRO, Australia (December)
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2.4.2. Activities 1999
B Th Verhagen attends RCM on the project Sustainable Water Resources and presents reports on the South African and Madagascar projects (February)
B Th Verhagen travels to Namibia on a joint mission with Dr K Froehlich of the IAEA to investigate the feasibility of that country's proposed project in the regional Sustainable Water Resources programme (April)
B Th Verhagen and M J Butler attend international Isotope Hydrology Symposium in Vienna and present paper and poster (May)
The IAEA accepts an EIG project proposal: Long-term isotope data series and the hydrological model of Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological systems to long term exploitation (June)
B Th Verhagen presents a paper to the International Conference of the Geological Society of Africa in Cape Town (July)
Delivery and commissioning of liquid scintillation spectrometer purchased by the IAEA under the regional model project (July/August).
sampling by M J Butler and B Th Verhagen of all Jwaneng production boreholes (July/August). This project is a continuation of a long-term investigation of the Jwaneng well field aquifer which shed much light on the geohydrology of the Kalahari.
B Th Verhagen visits Namibia to jointly initiate that country's programme under model project Sustainable Water Resources (August)
Following modifications, donated second mass spectrometer brought into operation (August)
During the past few years, considerable contributions have been made to problems of ground water pollution. Numerous smaller projects were completed with the private sector in 1998/99.
A tritium - oxygen-18 diagram of ground water and surface water from the Wurno irrigation area, NW Nigeria. The various components (upwelling deep ground water, irrigation and seasonal floods) of recharge to shallow ground water could be separated in order to predict vulnerability to ground water pollution.
2.5. Some Ongoing Projects
Isotope studies of thick unsaturated zones in semi-arid areas of southern Africa in the IAEA CRP on Isotope-based assessment of groundwater renewal and related anthropogenic effects in water scarce areas. Third project year.
IAEA projects RAF/8/022 in Nigeria and UG/8/002 in Uganda nearing completion. Assist Uganda in preparing final report.
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Work has started on the project: Long-term isotope data series and the hydrological model of Jwaneng mine northern well field as part of the new IAEA CRP: Isotope response of hydrological systems to long term exploitation.
Little Karoo fractured aquifer study. This is a joint study with the Department of Water Affairs, under contract to the Water Research Commission and partially under an IAEA technical operation contract.
Various smaller ad hoc projects, mainly on local water resource assessment and pollution issues with the private sector.
Ground water resources assessment in the Taaibosch fault zone, N Province. This is South Africa's component in the IAEA RAF/8/029 regional model project.
A recently initiated investigation of ground water resources in the south-east artesian basin, Namibia under RAF/8/029 IAEA regional model project
Five other projects, in Uganda, Tanzania, Kenya, Zimbabwe and Madagascar under RAF/8/029 are to be initiated within the immediate future.
The EIG has for some 15 years contributed tritium, deuterium and oxygen-18 data on monthly rain water samples collected from four southern African stations under the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP) as a national service free of charge.
2.6. Students and Teaching
I Mahomed, M Sc. Registration to be revised
J Kotze, PhD Joint supervision with the University of the Free State
M J Butler, MSc (1998) PhD to be registered when project proposal finalised.
The EIG has assisted in several Geology Honours projects
B Th Verhagen assists in teaching geohydrology to Geology Honours, part-time MSc and GDE classes
2.7. Future of the EIG
Activities in the immediate future of the EIG are likely to be dominated by the regional model project, which will involve training, scientific support and isotopic analyses in pursuance of the project. This endeavour is establishing research partnerships with six southern and eastern African states and strengthens operation with the Department of Water Affairs in South Africa.
Once the present re-organisation and rationalisation of the Environmental Isotope Laboratory is completed, active endeavours will be made to attract more post-graduate students.
With the passing of the new water act in South Africa the State has to assume greater responsibilities in the management of water resources. Isotope hydrology has been identified as an important tool in providing basic data on e.g. ground water systems and the EIG is seen as an important national asset. Following the drawing up of a Country Programme Framework (CPF) for IAEA support under its
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Technical Cooperation Programme, sustainable water resources and isotope hydrology as a key initiative in support of this goal is high on the agenda for research proposals recently called for by the NRF. Various proposals will be submitted by the EIG, including developing approaches to fractured rock aquifer studies, isotopic studies of the origins of nitrates; the role of radon as a ground water tracer; refining recharge estimates using environmental isotopes; national ground water vulnerability mapping - an extension of an initiative recently initiated with the Department of Water Affairs; ground water pollution studies using a variety of isotopes including tritium in landfill leachate; extending the national data base on isotopes in precipitation, surface water and ground water.
The EIG, with its modern low-level counting capacity, two operational isotope ratio mass spectrometers and a third state of the art instrument expected shortly, along with the Hugh Alsopp isotope laboratory and facilities in the Department of Geology, will place the University in a very favourable position to compete for housing the proposed National Isotope Facility. This may in time be further complemented by the development of accelerator mass spectrometry at the Schonland Research Centre.
3. Applied Nuclear Physics Programme
This programme concentrates on the detailed understanding of nuclear interactions with a view to their application to practical problems. In view of the over-all philosophy of the group and its aims these have primarily been in the mining industry. The most active project at present is that of Resonance Neutron Radiography.
3.1. Resonance Neutron Radiography
This project is a collaboration between the University, the Mineral Processing Division of De Beers, the Department of Nuclear Engineering at MIT, the South African Atomic Energy Corporation and Brookhaven National Laboratory. There are many different facets to it. It is based on the development of element sensitive neutron radiography based on resonances in the neutron cross-section plotted as a function of neutron energy.
The imaging process depends on the ration between the macroscopic cross-sections for the feature of interest and for the material in which the feature occurs.
There are two major regions of interest. One is at the oxygen “hole” around 2.3 MeV and the other is in the region of the resonance between 7.4 and 8.3 MeV. It turns out that the physics of neutron production favours the high energy resonance using the reaction 2H(d,n)3He with 5 MeV deuterons produced by an accelerator. This could be a cyclotron or an RFQ accelerator.
This project has gone through a number of different phases. In the initial phase (started effectively in 1993) use was made of the accelerators at the National Accelerator Centre, the Schonland Centre and the AEC. In 1994 the Group Leader spent a short sabbatical at MIT (sponsored by De Beers). After his return, a 2MeV RFQ accelerator was installed in the Neutron Source Laboratory at the Schonland as part of this ‘proof of principle” phase. De Beers contributed some R500 000 to the University in full support of the temporary acquisition of this accelerator.
The Group has continued its active involvement through a collaboration with MIT on an intermittent gas target, and research on the physics of the imaging process. This research is still continuing.
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This programme involves three PhD students, two full time and one part-time (R. Ambrosi, H. Rahmanian and J. Guzek). The part time student has successfully submitted his thesis and should graduate later this year. The other two students should submit next year.
The work by Richard Ambrosi is particularly interesting, involving the use of an amorphous silicon imaging panel of a type that is being developed for medical x-ray diagnostic applications. This panel has been characterised by the candidate and it should prove extremely useful in the future. This puts the University at the forefront of research into imaging with the purchase of this panel. Some R400 000 was raised from De Beers for this purchase.
The thesis of J. Guzek has concentrated on the investigation of the physics of neutron production and the optimisation of this aspect of the project. In addition he has been concerned with the integration of the techniques into a practical system.
This work has lead to many research papers in international journals or reviewed conference proceedings, and a number of presentations at local and international conferences including five invited papers.
It has also lead to a number of patents held jointly with De Beers and owned by De Beers. Through this programme this group has achieved recognition as one of the world leaders in fast neutron radiography.
The programme has brought considerable financial resource into the University. This includes the provision of an accelerator for a year and running expenses as well as student support. This year we had about R330 00 of support from the THRIP programme and this money will be used to purchase a new camera for imaging purposes. It is estimated that the total value of this support over the last six years is in the region of R3m.
3.2. On-line Analysis and Sorting
This programme has supported a number of projects aimed at investigating the fundamental nuclear interactions and detection methods that can be used for on-line analysis and sorting. These include inelastic scattering reactions with carbon for the analysis of the energy content of coal and the gold content of gold ore. This last reaction: 197Au(n,n’)197mAu was the subject of research leading to the award of an MSc degree to T. Magagula in 1998. He investigated this reaction using neutrons produced through 7Li(p,n)7Be on the Schonland tandem accelerator with a lithium target. He investigated how the neutron spectrum from this reaction could be used to excite the gold without exciting reactions with silicon and aluminium and so achieve the optimum limit of detection for gold in rock. The results were presented at the ECART Conference in the Netherlands in 1997.
With the new developments in accelerator technology being pioneered on the previous project, this idea could become practically feasible and a low energy high current accelerator with a gas target should be investigated. The correct energy could be found by varying the angle of emission of the neutrons. An idea that is being developed is to do this as a project with De Beers with support from the DACST Innovation Fund.
Projects on on-line analysis of coal and other systems will also be pursued under this heading. Another idea that is being developed is that of applying a variant of the resonance neutron radiography technique that has been developed to the determination of explosives and other
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contraband such as drugs. This depends on the use of the fact that the energy of the neutrons varies with the angle of emission. Therefore images of the different elements, nitrogen, carbon and oxygen could be obtained as the specimen moves around the source. Once again this is being pursued in a collaboration with DeBeers.
4. Programme on Radiation in the Environment
The importance of the environmental effects of radiation is increasing. This applies to the products and results of mining and of power generation as well as the natural background. For a number of years the group has been involved in the use of gamma-ray spectroscopy to measure radioactivity (principally from radium, the daughter of uranium) in mining products; mainly in zircons from beach sands.
As a result of this work and new analytical ideas that were developed, the Group was commissioned to design and build a gamma-spectroscopy system to measure the amounts of uranium and thorium in these products. This system was delivered to Richard’s Bay Minerals in 1997 and the money raised in this way has been used as a source of funding for the group’s research.
In addition the International Atomic Energy Agency sponsored programme on post-graduate education in Radiation Protection is associated with the Group. In this endeavour there is a close collaboration with the Health Physics Service of the University under Dr T. L. Nam and with the South African Council for Nuclear Safety. The Head of the Group is also the Director of the Centre for Post-Graduate Education in Radiation Protection. This Centre has been equipped with about R1.5m worth of equipment over the past few years by.
There are a number of post-graduate programmes associated with this initiative.
4.1. Projects on Radon in the Environment
A PhD candidate Alex Tsela has submitted a thesis on the measurement and evaluation of the emanation coefficient of radon from zircons. In this project an original way was developed for measuring the radon emitted from very small samples of well characterised mineral grains. This work has lead to a greater understanding of the emanation process in zircons and to the identification of anomalies in this behaviour. This work is being carried out in collaboration with Anders Damkjaer of the Risø Research Institute in Denmark and for some time it was part of the focus of a collaboration with the University of Swaziland..
A second PhD programme has been started on radon with David Maina from the Institute for Nuclear Research at the University of Nairobi. He spends some four months each year with the Group. His project is concerned with the health effects of smoke from cooking fires in rural dwellings combined with radon in the air. There is recognised epidemiological evidence that people who smoke cigarettes and are exposed to radon have significantly higher incidences of lung cancer. The objective of this project is to investigate whether there is a similar effect from indoor cooking fires in rural dwellings in Kenya and South Africa.
Many people in Africa live in dwellings with earth floors. The radon emission is therefore expected to be higher relative to dwellings with concrete slab floors. In addition if people sleep on the floor or close to it, thoron might be an issue. Some areas where there are beach sands for example have
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regions where the heavy minerals are concentrated. These regions could have high concentrations of radon, and thoron close to the ground. This project is very interesting and could be of great importance to the respiratory health of rural communities.
An allied project is being undertaken together with the Environmental Isotopes Laboratory in order to measure radon in ground water using the technique of liquid scintillation counting.
4.2. Gamma-ray Spectroscopy for Environmental Samples
The Schonland Centre should be a centre of excellence for the measurement of radiation. A sensitive method of gamma-ray spectroscopy was developed in the Group that can be used to monitor radium daughters (214Pb and 214Bi in the uranium chain) and 208Tl in the thorium chain. This method makes use of Marinelli beakers and a 5” x 5” NaI(Tl) detector. The detector is stabilised using a method developed by Hugo Andeweg at the Schonland and works well giving very accurate results.
The method has been used over a number of years to monitor the uranium and thorium in mineral products for export (mainly zircon). As was mentioned above, a semi-commercial instrument based on this principle was also supplied to Richard’s Bay Minerals. At present the software for this instrument is being revised.
This technique is being used for the measurement of radium in effluent from slimes dams, in an honours project with the department of Geology. This research is being inhibited by the need for the stabiliser on this instrument in the same way as the one supplied to RBM.
4.3. Post-graduate Centre for Radiation Protection
The new Centre for Post-Graduate Education in Radiation Protection has been developed at the Schonland Centre in association with the AEPRG and the University’s Health Physics Service as well as the Council for Nuclear Safety.
The equipment for this Centre, worth about R1.5m, was provided by the IAEA. The course is being given at present to 19 students from all over Africa (including three from South Africa). The fees for the overseas students are being paid by the Centre in a complicated arrangement with the IAEA. Some 12 of the students have registered for the Post-Graduate Diploma in the Sciences.
This Centre will form the focus for post-graduate research in the field of environmental radiation. The students who successfully complete the diploma can proceed to an M.Sc by examination and research report. It is expected that a great deal of this research will be carried out in association with the AEPRG as well as with the Health Physics Service and the CNS.
So far one application has been received from a student who wishes to undertake an MSc by research as part of this programme and there have been a number of other enquiries. With the decision to proceed with the initial stages of evaluation of the Pebble Bed Power Reactor concept, there will be an increasing demand for trained personnel in this field.
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Publications 1998-1999
B TH VERHAGEN, Environmental Isotope Hydrology, Hydrogeology of the Main Karoo Basin: Current Knowledge and Future Research Needs. Water Research Commission, Pretoria (1998).
NL INGRAHAM, A E CALDWELL and B TH VERHAGEN Isotope tracers in catchment hydrology. Chapter in book: Arid zone catchments. Elsevier Science Publishers, Amsterdam, (1998) 839 pp.
BTH VERHAGEN, MJ BUTLER, Environmental isotope studies of urban and waste disposal impact on groundwater resources in South Africa, In: Isotope Techniques in the study of Environmental Change. IAEA, Vienna, (1998) 411 - 422.
BTH VERHAGEN, Isotope Hydrology: applications to mining, urban, and pollution problems in southern Africa., Procs ICARID International Conference, NAARI, Mumbai, 4 - 7 February 1998, 307 - 324.
BTH VERHAGEN, Isotope Hydrology: a success story in the application of nuclear techniques to environmental problems, Nuclear Technology Conference, Mmabatho, October 1998.
A FOURIE, BTH VERHAGEN, M LEVIN, HD ROBINSON, Tritium as an indicator of contamination from landfill leachate,Wastecon '98 Conference, Kempton Park, October 1998.
BTH VERHAGEN, M LEVIN, AB FOURIE, High level tritium in leachate from landfill sites in the Republic of South Africa with emphasis on its distribution and value as an environmental tracer,Water Institute of South Africa Conference, WISA'98, Cape Town, May 1998, 10pp.
BTH VERHAGEN, Environmental isotope hydrology: past, present and future impacts on ground water studies in mining, the urban environment and understanding hydrochemistry, Procs Geocongress '98, Geological Society of South Africa, (1998) 285 - 288.
BTH VERHAGEN, Arid Zone Isotope Hydrology - Cooperation with the Geological Survey, Botswana, International Conference on the Role of a National Geological Survey in Sustainable Development, Lobatse (1998) p37.
BTH VERHAGEN, Case studies on isotope hydrology in the Kalahari,UNESCO/IHP Regional Workshop: Water Resources of the Kalahari Desert, Lobatse, Botswana, 3 - 5 November 1998.
MJ BUTLER, BTH VERHAGEN,Isotope studies of thick unsaturated zones in semi-arid areas of southern Africa,Progress Report on: International Atomic Energy Agency Research Contract Number: 335.F3.30.08 to Research Coordination Meeting, Sfax,Tunisia, 9 - 13. 12. (1998) 21pp. SRCNS 98/08.
BTH VERHAGEN,Investigation of leakages from the Aonob Dam, Namibia. ,Report on project RAF/08/026 mission (15 - 19 December 1997) to the International Atomic Agency (1998) 5pp. SRCNS 98/09.
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BTH VERHAGEN, Isotopes for groundwater development, Uganda ,End of Mission Report to the International Atomic Energy Agency. Project: UGA/8/002 - 01, 10 - 18 January 1998, SRCNS 98/10, 7pp.
BTH VERHAGEN, Isotopes for groundwater development, Ethiopia,End of Mission Report to the International Atomic Energy Agency, Project: RAF/8/022 15 01, 19 - 28 Jauary 1998, SRCNS 98/11, 8pp.
BTH VERHAGEN (1999) Environmental Isotope Hydrology. Chapter in book: Hydrogeology of the Main Karoo Basin: Current Knowledge and Future Research Needs. Water Research Commission, Pretoria. In press.
B TH VERHAGEN, M LEVIN and A FOURIE (1998) High level tritium in leachate from landfill sites in the Republic of South Africa with emphasis on its distribution and value as an environmental tracer. WISA ‘98, Water Institute of Southern Africa, Biennial Conference, 4-7 May, Baxter Theatre Centre, Cape Town.
A FOURIE, B TH VERHAGEN, M LEVIN and H D ROBINSON (1998) Tritium as an indicator of contamination from landfill leachate. Wastecon í98, 13-15 October, Kempton Park.
M LEVIN and B TH VERHAGEN (1999) A unique approach to evaluate the utility of landfill monitoring boreholes. ISSMGE, 12th African Regional Conference, Geotechnics for developing Africa. 25-27 October, Durban.
B TH VERHAGEN, D B BREDENKAMP, H JANSE VAN RENSBURG and J L FARR (1999) Recaharge quantification with radiocarbon: independent corroboration in three Karoo aquifer studies in Botswana. In: Procs International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA, Vienna
B TH VERHAGEN (1999) Isotope hydrology in Africa. In: Procs 11th International Conference of the Geological Society of Africa. Cape Town, South Africa.
M J BUTLER (1998) Ground water pollution at sanitarylandfill sites: Geohydrological, environmental isotope and hydrochemical studies. MSc Dissertation (Geology) University of the Witwatersrand, Johannesburg.
M J BUTLER and B TH VERHAGEN (1999) Trutium in waste as a tracer of landfill leachate in surface and ground water in South Africa. Poster presentation in: Procs International Symposium on Isotope Techniques in Water Resources Development and Management. IAEA, Vienna
Papers at International Conferences. 1998-1999
1 Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza, Accelerators and non-destructive measurement in the minerals industry (Invited paper).
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2 Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, J. I. W. Watterson, R. M. Ambrosi,. H. Rahmanian and J. Guzek,, Experimental verification of computer image formation in accelerator fast neutron radiography (Invited paper).
3 Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, R. M. Ambrosi and J. I. W. Watterson, The relationship between contrast, resolution and detectability in fast neutron radiography.
4 Fifteenth Int. Conference on the Application of Accelerators in Research and Industry, University of North Texas, Denton, Texas, November 1998, H. Rahmanian and J. I. W. Watterson, Neutron energy discrimination using a proton radiator and a phosphor layer.
Publications in Refereed Journals and Conference Proceedings(Recognised by the S. African Department of National Education)
1. J. Guzek, K. Richardson, C.B. Franklyn, A. Waites, W. R. McMurray, J. I. W. Watterson and U. A. S. Tapper Development of a high pressure deuterium gas target for the generation of intense mono-energetic fast neutron beams. Nucl. Instr. and Methods in Phys. Res. ? (1998) ?-?
2. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian, J. Guzek, U. A. S. Tapper and R.C. Lanza, Accelerators and non-destructive measurement in the minerals industry. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
3. J. I. W. Watterson, R. M. Ambrosi, H. Rahmanian and J. Guzek, Experimental verification of computer image formation in accelerator fast neutron radiography. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
4. R. M. Ambrosi and J. I. W. Watterson, The relationship between contrast, resolution and detectability in fast neutron radiography. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, (1999) 1078 - 1083.
5. R.M. Ambrosi, J.I.W. Watterson, The effect of air cavities on the dose delivered to the lung during high-dose brachytherapy. Biological Trace Element Research vols 71 – 72 (1999) 499-507
6. H. Rahmanian and J. I. W. Watterson, Neutron energy discrimination using a proton radiator and a phosphor layer. Applications of Accelerators in Research and Industry, Proceedings of the Fifteenth International Conference, Denton, Texas, November 1998, J.L. Duggan and I. L. Morgan eds, AIP Conference Proceedings, In Press.
Patents
1 U. A. S. Tapper, G.W. Over, J Guzek, H. Rahmanian and J. I. W. Watterson, Scintillation detector, S.A. Patent 95/5218.
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2 U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron beam generator, S.A. Patent 95/7686.
3 K. Richardson, U. A. S. Tapper, J Guzek and J. I. W. Watterson, Neutron radiography gas target, S.A. Provisional Patent H0613.224.
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ION IMPLANTATION AND SURFACE STUDIES RESEARCH PROGRAMME
Leader: Prof. T.E. Derry, Reader in Ion-Crystal Interactions, Physics Department.
Participating academics:
________________________________________________
name |department | time spent
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(Prof) T.E. Derry |Physics | 50 %
(Prof) J.F. Prins* |Schonland (sec) | 90 %
(Prof) J.D. Comins |Physics | 5 %
(Dr) G. Hearne |Physics | 5 %
(Prof) A.T. Davidson |Zululand Univ. |
(Prof) V. Hoffmann |Tübingen Univ. |
---------------------------------------------------------------------
* note -- Prof. Prins is seconded from De Beers, whose Diamond Electronics Programme he manages, and although attached to the Ion Implantation & Surface Studies Research Programme, he directs his research independently, making use of our facilities.
Objectives & Rationale:
(1) To promote research which is already well-established at the SRCNS, on ion-beam modification
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and/or ion beam analysis (supplemented by other spectroscopies) of the (near) surface of technologically important and fundamental solids -- diamond, metals, ionic crystals, catalysts, and other materials. The principal research instruments are an ion implanter, small accelerator and UHV surface-science chamber, interconnectable.
(2) To foster the existing collaborations with industries, other institutions (including HBU's) and internationally. The Schonland ion-implantation group provides a centre of both equipment and expertise for the research of others, as well as its own. The research provides a springboard for overseas collaborations, via both overseas visits and visitors from overseas.
(3) To continue to train postgraduate students, who find our combination of pure and applied physics stimulating, and to provide a variety of undergraduate projects for students of all races. Some dozen research students have now graduated, many finding ready employment in industry.
The past year has been a successful one, with Prof. Prins publishing many research and review papers, and rapidly becoming an invited celebrity on the international conference circuit. Prof. Derry was elected to the Fellowship grade of the British Institute of Physics.
Research Projects:
1 (a) Investigation of the amount and position of oxygen atoms on diamond surfaces Using Rutherford backscattering and resonant ion scattering, and transmission channelling.
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Personnel: T.E. Derry, D.B. Rebuli (student), plus WNAC membersThe research has possible implications for the chemical-vapour deposited diamond layer industry. Mr D Rebuli has obtained his M.Sc and written several papers (see publications lists).
(b) Functional form of the oxygen on diamond surfacesUsing fourier transform infra-red spectroscopy; a collaboration with Tübingen University.Personnel: T.E. Derry, V. Hoffmann (Tübingen)A sabbatical by T.E. Derry (February-July 1998) initiated this work, which has continued with another brief visit to Tübingen in 1999. The results so far are promising.
2 (a) Attempt to produce carbon (diamond) epitaxy on copper single crystalsUsing ion implantation, Auger spectroscopy, possibly ion channelling.Personnel: J.F. Prins, S.R. Naidoo (student)This is an industry collaboration (De Beers); success would be the key to the diamond semiconductor industry, and would place South Africa at the forefront. Work continued in 1998 using the upgraded Auger hardware and software.
(b) Improvement of diamond doping Using ion implantation and electrical measurements, plus development of the theory.Personnel: J.F. Prins, S.R. Naidoo (student), H. van Heerden A further industry collaboration (De Beers) with a view to developing the next millennium’s diamond semiconductors. Both p- and n-type doping (using B and P respectively) continue to be improved, and good n-type doping using oxygen implants has recently been patented. Prof. Prins will seek further improvement using high-energy implants in the U.K.
(c) Electron-injection junctions and blue luminescence in diamond Using implantation, electrical measurements.Personnel: J.F. Prins, S.R. Naidoo (student) Industry collaboration (De Beers); part of the diamond semiconductors studies. Some of the work has been published during the review period.
(d) Metal-insulator transition in heavily doped diamondUsing ion implantation and electrical measurementsPersonnel: M.J.R. Hoch, J.F. Prins, T.S. Tshepe (student)A collaboration with members of the Physics Dept. Results have been published in papers and at conferences.
3 (a) Radiation damage in other substances: ionic oxides Using ion implantation and optical spectroscopy.Personnel: A.T. Davidson (Zululand) + students, T.E. Derry, J.D. Comins This represents our continuing University of Zululand collaboration.
(b) Radiation damage in siliconUsing ion implantation, surface Brillouin scattering.Personnel: J.D. Comins and other members of Physics Dept, T.E. Derry, X. Zhang (student)This collaboration with the Physics Dept has produced both journal and conference papers.
(c) Implantation and radiation damage in InSnO4
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Using both low and high energy implantations (the latter with the 1,4 MeV accelerator).Personnel: J.D. Comins, T.E. Derry, G. Amolo (student)This Physics Dept collaboration is relatively new.
4 (a) Attempt to synthesize the postulated ultrahard material C3N4 Proposed method: ion implantation, surface Brillouin scattering analysis of the layers.Personnel: S.B. Luyckx, J.D. Comins, T.E. Derry, J.F. PrinsThe original collaboration with the Physics Dept has been on a back-burner, but some promising results have been obtained by Prof. Prins.
(b) High pressure diamond anvil cell studies Assisted by ion implantation of electrical contacts into the cell.Personnel: G. Hearne + students, S.R. Naidoo, T.E. Derry Another collaboration in progress with the Physics Dept.
5(a) Metal alloying and defects Using implantation, Mössbauer, ion channelling.Personnel: H. Pollak, T.E. Derry, J.K. Dewhurst (student), H. de Waard (Groningen)This interesting cross-disciplinary project with overseas networking had initial success, but is now concluded with the decease of Prof. Pollak.
(b) Tungsten carbide studiesUsing ion implantation or ion beam analysis.Personnel: T.E. Derry, S.B. Luyckx.Recent work for Boart Longyear (both here and in Ireland) has involved the ion-beam analysis of trace amounts of boron in their and others’ product.
(c) Surface engineering for industry Using ion implantation Personnel: T.E. Derry, H. van Heerden, S.B. Luyckx There are industry collaboration possibilities here if the FRD/NRF were to facilitate and maintain industrial enthusiasm, but no new projects have been offered as yet.
6 Synthesis and promotion of catalysts by novel routes Using ion implantation (including into powders), XPS.Personnel: N.J. Coville (Chemistry), T.E. Derry, H. van Heerden A project with cross-disciplinary networking and industry collaboration, which was very active in the past, and still of potential interest to the Chemistry Department.
7 Services to continue: Support of other universities by provision of service implants (e.g. Pretoria, Cape Town, Durban-Westville): regularly continuing.Availability of the UHV electron spectrometer for surface analyses by othe (paying) institutions.
Ion Implantation and Surface Studies Research Programme
plus collaborators
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PUBLICATIONS FOR 1998:
WJ Huisman, M Lohmeier, HA van der Vegt, JF Peters, SA de Vries, E Vlieg, VH Etgens, TE Derry, JF van der Veen.Evidence for Tilted Chains on the Diamond(111)-2x1 Surface Surface Science 396, pp 241-252
X Zhang, JD Comins; AG Every, PR Stoddart, W Pang, TE DerrySurface Brillouin Scattering Study of the Surface Excitations inAmorphous Silicon Layers Produced by Ion BombardmentPhysical Review B 58, 13677-13685
X Zhang, JD Comins, AG Every; PR Stoddart, W Pang, TE DerryStudy of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin ScatteringProceedings of the 16th International Conf on Raman Spectroscopy, September 1998, pp 884-887
JF PrinsRecombination Luminescence from Defects in Boron-ion Implantation-doped Diamond using Low FluencesMaterials Research and Innovations 1, pp 243-253
JF PrinsUltraviolet Cathodoluminescence from Diamond Layers after Dopingby means of Boron-ion ImplantationApplied Physics Letters 73, pp 2308-2310 (1998)
JF PrinsIon Implantation of Diamond Below the Amorphization Threshold:Defects, Impurities, and their InteractionsProceedings of the 5th NIRIM International Symposium on Advanced Materials,Tsukuba, March 1998; publ National Institute for Research in InorganicMaterials, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; pp 93-96
JF PrinsRecent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of Ion ImplantationDiamond Films and Technology 8, 181-194 (1998)
JF PrinsDoping of Diamond by the Diffusion of Interstitial Atoms into Layers Containing a Low Density of VacanciesDiamond and Related Materials 7, 545-549 (1998)
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JF PrinsIon Implantation of Diamond Below the Amorphization Threshold:Defects, Impurities, and their Interactions (invited paper)5th NIRIM International Symposium on Advanced Materials, Tsukuba, March 1998
JF PrinsRecent Results on the Preparation of Doped Layers, Contacts, and Interfaces in Diamond by Means of Ion Implantation (invited paper)Name of Journal/Book/Magazine/Report/Conference 2nd International Symposium on Diamond Electronic Devices, Osaka,March 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JPF SellschopOxygen on Diamond SurfacesSAIP Conference, Cape Town, July 1998
T Tshepe, JF Prins, MJR HochConductivity Studies in Boron-ion Implanted Type IIa DiamondSAIP Conference, Cape Town, July 1998
SR Naidoo, JF PrinsCarbon Overgrowths on Copper by Ion ImplantationSAIP Conference, Cape Town, July 1998
WJ Huisman, JF Peters, SA de Vries, E Vlieg, JF van der Veen, TE Derry Synchrotron Radiation Determination of Atomic Positions on the Diamond(111) Surface Before and After ReconstructionAnnual Diamond Conference, London, July 1998
JF PrinsActivation of, and Vacancy Interactions with, Large Dopant Atoms in DiamondAnnual Diamond Conference, London, July 1998
E Sideras-Haddad, D Rebuli, TE Derry, SH Connell, JPF Sellschop, BP Doyle, RD Maclear,Oxygen on DiamondAnnual Diamond Conference, London, July 1998
DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JM Butler, JPF Sellschop Oxygen Surface Studies in Ultra-thin Diamonds using Transmission Channelled Rutherford Forward ScatteringInternational Microprobe Conference, Cape Town, August 1998
DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF Sellschop, Oxygen on Diamond SurfacesInternational Conference on New Diamond Science and Technology, Pretoria, September 1998
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SR Naidoo, JF PrinsElectroluminescence from Electron Injection Junctions Created by Carbon and Phosphorus Ion ImplantationInternational Conference on New Diamond Science and Technology, Pretoria, September 1998
T Tshepe, JF Prins, MJR HochMetal-Insulator Transition in Boron-Ion Implanted Type IIa DiamondInternational Conference on New Diamond Science and Technology,Pretoria, September 1998
X Zhang, JD Comins,’ AG Every, PR Stoddart, W Pang’ TE DerryStudy of the Surface Excitations in Ion-bombarded Silicon Layers by Surface Brillouin Scattering16th International Conference on Raman Spectroscopy, Cape Town, September 1998
PUBLICATIONS FOR 1999:
D Rebuli, P Aggerholm, JE Butler, SH Connell, TE Derry, BP Doyle, RD Maclear, JPF Sellschop, E Sideras-HaddadOxygen Surface Studies in Ultra-thin Diamond Using a Resonance Reaction and Transmission Channelled Rutherford Forward ScatteringNuclear Instruments and Methods B158 (1999) 701-705
DB Rebuli, TE Derry, E Sideras-Haddad, B Doyle, RD Maclear, SH Connell, JPF Sellschop,Oxygen on Diamond SurfacesDiamond and Related Materials 8 (1999) 1620-1622
SR Naidoo, JF PrinsElectroluminescence from Electron Injection Junctions Created byCarbon and Phosphorus Ion ImplantationDiamond and Related Materials 8 (1999) 1502-1507
T Tshepe, JF Prins, MJR HochMetal-Insulator Transition in Boron-Ion Implanted Type IIa DiamondDiamond and Related Materials 8 (1999) 1508-1510
SR Naidoo, JF PrinsRaman and Auger Spectroscopy Studies on Ion Implanted DiamondSAIP Conference, Port Elizabeth, July 1999
G Amolo, JD Comins, DS McLachlan, TE DerryStructural Damage of Tin-doped Indium Oxide (ITO) by 1MeV ProtonsSAIP Conference, Port Elizabeth, July 1999
JF PrinsMetastable Dopant States in DiamondAnnual Diamond Conference, Oxford, July 1999
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T Tshepe,JF Prins, MJR HochThe Metal-insulator Transition in DiamondAnnual Diamond Conference, Oxford, July 1999
JF PrinsOxygen Donor States in DiamondAnnual Diamond Conference, Oxford, July 1999
JF Prins, TE DerryRadiation Defects and their Annealing Behaviour in Ion ImplantedDiamonds (invited paper)10th Internat Conf on Radiation Effects in Insulators, Jena, July 1999
JF PrinsFunctional Materials: Physics and Chemistry of Semiconductors: DiamondEncyclopaedia of Materials: Science and Technology (in press)Chapter in Book
JF Prins, TE DerryRadiation Defects and their Annealing Behaviour in Ion-implanted DiamondNuclear Instruments and Methods (in press)
Conferences and visits(1) 5th NIRIM International Symposium on Advanced Materials, Tsukuba (Japan) March 1998Attending: J.F. Prins (chairman, presenter)
(2) 2nd International Symposium on Diamond Electronic Devices, Osaka (Japan), March 1998Attending: J.F Prins (chairman, presenter)
(3) European Materials Research Society Spring Meeting, Strasbourg (France), June 1998Attending: T.E. Derry
(4) Annual Diamond Conference, London (UK), July 1998Attending: J.F. Prins, T.E.Derry (both presenting)
(5) South African Institute of Physics Conference, Cape Town, July 1998Attending: D.B. Rebuli (presenter), S.R. Naidoo.
(6) International Microprobe Conference, Cape Town, August 1998Attending: D.B. Rebuli (presenter)
(7) International Conference on New Diamond Science and Technology, Pretoria, Sept 1998Attending: J.F. Prins (Organizing Committee Chairman), T.E. Derry, D.B. Rebuli, S.R. Naidoo (all presented papers).
(8) South African Institute of Physics Conference, Port Elizabeth, July 1999Attending: S.R. Naidoo, G. Amolo (presenting), T.E. Derry (chairing).
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(9) Annual Diamond Conference, Oxford (UK), July 1999Attending: J.F. Prins (presenter).
(10) 10th Internat Conf on Radiation Effects in Insulators, Jena (Germany), July 1999Attending: T.E. Derry (presenter).
T.E. Derry spent the period from February to July 1998 on study-leave at the University of Tübingen (Germany) helping to set up measurements to reveal the environment of the hydrogen and oxygen (or other) atoms on polished diamond surfaces using infra-red spectroscopy.
Post-graduate Students
0910017O S.R. Naidoo (M.Sc now converted to Ph.D), registered Jan 1995 (part-time).Topic: Carbon overgrowths on copper by ion implantation, supervisor: J.F. Prins9201400E D.B. Rebuli (M.Sc), registered Jan 1996, submitted and degree granted 1999.Topic: "Ion Beam Analysis of Oxygen on Diamond Surfaces", supervisor: T.E. Derry.
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Annual Report 1998-99 for Research Programme
Based at the Schonland Research Centre
1. Name of programme
4.3.1. Nuclear Physics Programme
2. Programme Leader
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department)
3. Members of the Nuclear Physics Group Pursuing the Programme
Professor V. Hnizdo (Reader in Nuclear Physics, Physics Department, Wits, resigned June 1999)
Dr J. Carter (Senior Lecturer, Physics Department, Wits, Staff number 603953, percentage time spent on research activities 35%)
Dr. R.W. Fearick (Senior Lecturer, Physics Department, UCT).
Professor B. Spoelstra (Physics Department, University of Zululand).
The members of the Nuclear Physics Group have enjoyed a longstanding and ongoing collaboration which includes the corresponding groups at the National Accelerator Centre, Faure, the Florida State University, USA, the Triangle Universities Nuclear Laboratory, USA, and the Technical University, Darmstadt, Germany.
4. Research Projects
(a) Professor V. Hnizdo (principal investigator)
(i) Research into the implications of the so-called hidden mechanical momentum of macroscopic bodies in classical electrodynamics has continued, yielding a series of papers in the American Journal of Physics.
(ii) A major calculational study of the geometric factors in the classic analysis of the masurability of the electromagnetic field of Bohr and Rosenfeld has been published. Using the calculational methods of this paper, the electromagnetic “self-force” on a spherical test body has been evaluated in closed form, which enabled us to refute the conclusions of a recent revision of the Bohr-Rosenfeld analysis that were at variance with the results of the latter work.
(iii) The continuing investigation into nuclear structure effects in light heavy-ion scattering reactions was carried out at the Tandem accelerator of the Schonland Centre. This led to the award of an MSc degree to J. Madonsela in December 1998.
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(b) Dr J. Carter (principal investigator)
(i) Data were obtained in 1997 at the Cyclotron Facility of the National Accelerator Centre in the latest of a series of experiments investigating the excitation and decay of giant resonances in nuclei. This involved the participation of colleagues from Darmstadt. Subsequent data analysis was undertaken during a sabbatical visit of three months to Darmstadt in 1998 and a another visit of one month in 1999. This work is currently being prepared for publication.
(ii) An ongoing programme of light heavy-ion scattering is being pursued at the Tandem accelerator, Schonland Centre. Recently two major publications were produced, one associated with a PhD degree and one with an MSc. The present work involving the scattering of 9Be from 9Be together with existing data will lead to the third paper.
5. Publications 1998-99
V. Hnizdo, “Covariance of the total energy-momentum four-vector of a charge and current carrying macroscopic body,” American Journal of Physics 66 (1998) 414-418.
J. Carter, A.A. Cowley, H. Diesener, R.W. Fearick, S.V. Förtsch, M.N. Harakeh, J.J. Lawrie, S.J. Mills, P. von Neumann-Cosel, R.T. Newman, J.V. Pilcher, A. Richter, K. Schweda, F.D. Smit, G.F. Steyn, S. Strauch and D.M. Whittal, “Isoscalar quadrupole strength in 40Ca from the (p,p’o) reaction at Ep = 100 MeV,” Nucl. Phys. A 630 (1998) 631.
V. Hnizdo, “Radiation from circling relativistic charges, comment on a paper by Gordeyev,” Am. J. Phys. 66 (1998) 847.
V. Hnizdo, “Comment on: An exactly solvable two-body problem with retarded interactions and radiation reaction in classical electrodynamics,” J. Math. Phys. 39 (1998) 5663.
V. Hnizdo, “Common misrepresentation of the Einstein-Podolsky-Rosen argument,” Found. Phys. Lett. 11 (1998) 359-370.
V. Hnizdo, “Geometric factors in the Bohr-Rosenfeld analysis of the measurability of the electromagnetic field,” J. Math. Phys. 32 (1999) 2427-2445.
V. Hnizdo, “Comment on ‘Limits of the measurability of the local quantum electromagnetic field amplitude, ” Phys. Rev. A, in press (1999).
V. Hnizdo, “On the Laplacian of 1/r,” Eur. J. Phys., submitted (1999).
H. Diesener, U. Helm, H. Miska, P. von Neumann-Cosel, A. Richter, G. Schrieder, A. Stascheck, A. Stiller, H.J. Emerich, G. Fricke, T. Kroehl and J. Carter, “Giant resonance spectroscopy of 40Ca with (e,e’x) reaction (I): Experiments and overview of results,” Phys. Rev. C, submitted (1999).
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H. Diesener, U. Helm, V. Huck, P. von Neumann-Cosel, C. Rangacharyulu, A. Richter, G. Schrieder, A. Stascheck, S. Strauch, J. Ryckebusch and J. Carter, “Giant resonance spectroscopy of 40Ca with the(e,e’x) reaction (II): Multipole decomposition of 4 integrated spectra and angular correlations,” Phys. Rev. C, submitted (1999).
H. Diesener, U. Helm, G. Herbert, P. von Neumann-Cosel, A. Richter, G. Schrieder, S. Strauch and J. Carter, “Giant resonance spectroscopy of 40Ca with the (e,e’x) reaction (III): Semidirect versus statistical decay,” Phys. Rev. C, submitted (1999).
B.M. Nangu, J. Carter, H. Machner, B. Spelstra, J. Pilcher, E. Sideras-Haddad, S.H. Connell, J.P.F. Sellschop, A.A. Cowley, D. Aschman, D. Steyn and K. Baruth-Ram, “Energy deposition and the origin of intermediate-mass fragments in mdedium-energy proton induced reactions,” in preparation.
6. Conferences and Visits
(i) V. Hnizdo: Research visit to Florida State University, Tallahassee, July 1998
(ii) J. Carter: Research visits to the Nuclear Physics Institute, Technical University, Darmstadt July/August/September 1998 and June/July 1999
7. Visiting Scientists
(i) Dr S.V. Förtsch, National Accelerator Centre, August 1999
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8. Higher-degree students 1998-99
Student
number
Name Degree First
Registration
Completion Topic Supervisor
9411102A J Madonsela MSc Mar 93 Nov 98 Nuclear V Hnizdo
9213310A B M Nangu MSc
Part-time
Feb 92 2000 Nuclear J Carter/B Spoelstra
MHLNCE001 N W Mhlahlo MSc Jan 98 2000 Nuclear R W Fearick
MBLGIV00X G.K Mabala PhD Jan 98 2001 Nuclear R W Fearick
MRRSEA003 S H T Murray MSc Jan 98 2000 Nuclear R W Fearick
Dr J. Carter
September 1999
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Report of the
WITS-Northern Accelerator Research Centre
within the
Schonland Research Centre for Nuclear Sciences
32
Description of the Research Centre ..................................................................................34
Group Membership............................................................................................................36
Research Projects...............................................................................................................37
Accelerator Laboratory Facilities......................................................................................51
Usage..................................................................................................................................54
Publications ......................................................................................................................56
Conferences and Visits .....................................................................................................60
Visiting Scientists .............................................................................................................67
Students .............................................................................................................................68
Version of 13.8.98
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The WITS-Northern Accelerator Research Group
(Director : Dr SH Connell)
The WITS-Northern Accelerator Research Centre research entity provides a common home for a range of research groups spanning basic physics, applied physics, industrial physics and various interdisciplinary sciences, such as nuclear geology and nuclear techniques in industry, bio-medicine, metallurgy and the environment.
The Particle-Solid Interactions Research Group(Leader : Dr SH Connell) : focuses on the phenomena associated with the interaction of accelerated beams and radiation with ordered materials. In the case that the material properties are well understood, then the basic physics aspects of the interaction are studied. In the inverse situation, the goal is materials physics. In all cases the research methodology involves accelerated beams, nuclear instrumentation, highly automated computer controlled data acquisition and processing, sophisticated engineering in the equipment construction and finally data interpretation via simulation of the experimental observables based on modern quantum mechanical models. Most of the work is carried out at the SRCNS, but where appropriate, regular use is made of CERN, TRIUMF, PSI and other major international facilities.
Nuclear-Interdisciplinary Science based on Ion-Beam Microscopies(Leader : Dr E Sideras-Haddad) : applies nuclear and atomic physics phenomena in the interaction of focused beams with small samples to perform a range of novel microscopies in collaborative interdisciplinary research projects. Accelerator Mass Spectrometry capability is currently being developed
The Nuclear Diamond Physics Research Group(Leader : Prof JPF Sellschop) : focuses particularly on new physics and resulting applications in specific areas at the interface of nuclear and diamond physics. Most of the work is carried out at the SRCNS, but where appropriate, regular use is made of CERN, TRIUMF, PSI, Grenoble, GSI Darmstadt and other major international facilities.
The Nuclear Geology Research Group(Leader : Dr RJ Hart) : pursues global geological topics relevant to modern theories of crustal and earth forming processes. Primarily geologists, they benefit from the synergy of a close association with novel nuclear techniques for a vital part of their sample characterisation.
The synergy, mutual operation and interdependence between these research groups includes the following points:
Nuclear and particle physics knowledge is either a goal or an important tool of the research thrust.
Nuclear techniques (accelerated particle beams, radioactivity, nuclear electronics and detection systems and computer systems for data processing, visualisation and process control) are used in the research programmes.
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Common major facilities. The most important major equipment items here are the two Van de Graaff accelerators with their associated infrastructure.
Postgraduate student training. The research group leaders believe the open environment of a large research facility facilitates the development of students due to the points mentioned above.
Coherence. The whole is greater than the sum of the parts.
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Group Membership
Name Department Staff No. Percentage Time
Dr SH Connell Physics : Senior Lecturer
08800031 40% lecturing
25% Lab Management
35% Research
Dr E Sideras-Haddad
Physics : Senior Research Officer
00675961 30% lecturing
25% Lab Management
45% Research
Prof JPF Sellschop Physics : Emeritus Professor
00911272 75% Research
25% National Advisory Committees
Dr RJ Hart Secondment : Council of Geosciences
09000631 40% Research
15% CGS line function
25% Lab Man
20% International Collaboration
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Research Projects
Impurity Chemistry and Dynamics in Diamond by In-beam Molecular Complex SpectroscopyStaff : SH Connell, JPF Sellschop, E Sideras-Haddad.Students : MG Bossenger, BP Doyle.Collaborators : H Appel (KFK Karlsruhe), K Bharuth-Ram (UDW), W Verwoerd (UNISA).This work involves basic research into the behaviour of defects and impurities in insulators and wide-band gap semiconductors. Defects and impurities play an important role in determining the physical, electrical, optical and chemical properties (among others) of materials. Using the EN-Tandem Accelerator, radioactive impurities are recoil-implanted into materials to study their geometrical, chemical and dynamical relationships in the host lattice and as complexes with other defects. A unique opportunity to visualise transient and stable molecular complexes formed immediately after ion-implantation is afforded (hot-atom chemistry). The data is reconstructed using the details of the hyperfine interaction of the probe nucleus with local fields. Diamond, other carbon allotropes, as well as various carbon containing molecules have been targeted as important materials for research. During the review period, attention has focused on analysis of previous data, writing papers, design and fund-raising for development of a heavy-ion pulsing system for the EN-Tandem (THRIPP program with DeBeers) as well as organising the 11th International Conference on Hyperfine Interactions at the end of August 1998.
Impurity Chemistry and Dynamics in Diamond by Perturbed Angular CorrelationsStaff : SH Connell, JPF Sellschop, E Sideras-Haddad.Students : BP Doyle, EJ StorbeckCollaborators : K Bharuth-Ram (UDW), H Pattyn (Leuven), W Verwoerd (UNISA), U Wahl (Leuven)This is the off-line source based activity version of the previous measurements, enabling later time windows to be accessed, allowing solid-state reactions to occur. A PAC project on 111In in diamond is ongoing as a complementary technique to the CEEC measurements mentioned further on. A new PAC facility has been developed. Conventional systems rely on many crates of fast electronics to process the signals. Our system is novel in that buffered event-by-event acquisition (COLLECT - see later section), enables software logic to extensively replace the expensive hardware systems, while still maintaining the data-rate of the larger systems. The project has been given a large boost with access being granted to the ISOLDE facility, CERN, Switzerland for implantation of exotic radioactive species. New software for the analysis of this data is being developed. These analyses are compared to the CEEC data taken on the same systems, and with theoretical calculations that have been made in collaboration with the Physics Department. Subsequently double implant experiments will also be done with the aim of studying the dynamical behaviour of In-X complexes. The PAC technique can label various complexes and follow their behaviour through various sample treatments with particularly simple sample preparation for the measurement process. These studies illuminate processes of diffusion, decoration, complexation, dissociation, trapping and detrapping in the solid state. This information is relevant to processes which lead to doping, passivation and poisoning phenomena in semi-conductors (in our case, semi-conducting diamond). There was substantial experimental activity during the year, and the results are being presented at the conference mentioned above, as well as being prepared for more detailed exposure in journals.
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Positron Spectroscopy studies of pure diamond, dilute bulk defects and surfaces.Staff : SH Connell, JPF Sellschop.Students : RWN Nilen, CG FischerCollaborators :A Alam (Bristol), W Anwand (Rosendorf), K Bharuth-Ram (UDW), G Brauer
(Rossendorf), DT Britton (UCT), P Coleman (East Anglia), F Malik (East Anglia), K Maier (Bonn, J Major (MPI-Stuttgart), A Seeger (MPI-Stuttgart), E Sendezera (U Zululand), H Stoll (MPI-Stuttgart), W Verwoerd (UNISA).
Positrons implanted into solids thermalise, diffuse rapidly, and finally form well defined configurations with the host lattice or its defects. Observation of the properties of the annihilation radiation allows a reconstruction of the local microscopic configuration by means of quantum mechanical models. In this way, detailed information concerning solid state parameters is measured. Spectra taken for the diamond host matrix demonstrate severe and hitherto unexplained anomalies. This anomalous behaviour of the positron in diamond has now been resolved following our measurements, calculations, and the calculations of our collaborators. Many papers have been published or are in preparation, including a review article. Following these advances, our programme has broadened from the positron-pure-bulk-diamond interaction to the studies of positron-defect and positron-surface interactions. A detailed set of experiments probing lattice effects in extended damage transport during ion-implantation, photochromic defects and surface structures as well as near-surface defects has been performed this year. The results are currently being published and prepared for publication.
Conversion electron emission channeling spectroscopyStaff : SH Connell, JPF Sellschop.Students : BP Doyle, EJ Storbeck.Collaborators :K Bharuth-Ram (UDW), H Hofsass (Konstanz), H Pattyn (Leuven), W Verwoerd
(UNISA), U Wahl (Leuven).
Ion implantation in diamond of radioactive nuclides such as 111In can be exploited to provide information on the environment in which the nuclide resides. In the emission of conversion electrons from the nuclide at its characteristic lattice sites in the diamond, the electrons are sensitive to the source-lattice configuration as well as the structure of the crystal through the channeling, blocking and flux peaking effects. The CEEC research is entirely complementary to the PAC study mentioned above, and the projects will be run simultaneously. The same comments apply then with respect to future research, as in the PAC section. A two-dimensional position and energy sensitive PAD detector was developed at CERN, Switzerland, originally as a high-energy physics tool, but now available to CEEC measurements. This detector is the of its kind to be used in this way and now allows the rapid collection of 2-dimensional channeling spectra. In two dimensions one is able to see both the axial and planar effects in channeling, enabling a more complete picture of the impurity lattice site. A profitable collaboration with K.U. Leuven has enabled the ISOLDE facility at CERN to be exploited by us. This allows implantation of the radioactive probe ions to the stringent specifications required for CEEC measurements. In order to explain the experimental results it is necessary to use solutions to the quantum mechanical theory of electron channeling. This demanded the development of an analysis program that takes into account the quantum nature of electron channeling. An important recent contribution is the inclusion of molecular effects in the construction of the transverse
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channeling potential, using Fourier methods based on the output from self-consistent quantum chemical simulations of large diamond-like molecules. There is experimental evidence that this was necessary, particularly in the case of channeling in diamond (<110> direction), where the electronic structure is not well approximated by the normal methods based on atomic scattering factors. Analysis of the large data sets obtained is well advanced. Results thus far indicate new perspectives on the annealing of the implant damage and concur with recent density functional theory calculations on the stable lattice site for the implanted and annealed In. This research is entirely complementary to the PAC study mentioned above, and the projects have been run simultaneously. The same comments as with regards future research apply here, as in the PAC section.
Muon Spin Rotation/Relaxation/Resonance (MSR) spectroscopy in diamondStaff : SH Connell, JPF Sellschop.Students : BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN NilenCollaborators :JM Baker (Oxford), K Bharuth-Ram (UDW), JE Butler (NRL-Washington), SFJ Cox
(Rutherford Lab), TL Estle (Rice U), T. Jestadt (Oxford). R Kiefl (TRIUMF), J Major (MPI-Stuttgart), P. Murphy (Oxford), R Scheuermann (MPI-Stuttgart), A Seeger (MPI-Stuttgart),
Muonium-defect interactions as well as muonium dynamics are being explored using Muon Spin Rotation/Relaxation/Resonance (MSR) spectroscopy. The current program takes advantage of the unique properties of the muon to probe the behaviour of the hydrogen-like atom in diamond. The importance of hydrogen as an impurity in diamond is widely appreciated. Its important catalytic role in the metastable synthesis of diamond, as well as its anticipated significance regarding the electronic properties of future diamond devices are two examples. Despite the relevance of hydrogen to diamond growth, properties and engineering, comparatively little is known about it, and it has proved to be a most difficult impurity to study using conventional techniques. On the other hand, most of the information on hydrogen in diamond has been inferred by the indirect technique of the MSR, which is sensitive, robust, accurate, and has a low background. Clear examples of muonium diffusion, trapping and detrapping, and possibly even Ionisation reactions at B acceptors in semi-conducting diamond have been both observed and modelled. The transparency of diamond and the photochromicity of certain defects was used to illuminate some of the processes involved. A new muonium site in diamond containing substantial amount of nitrogen-related defects was discovered. This has provided evidence for a new deep trap for hydrogen in diamond, as well as a new way to study one of the nitrogen related defects whose structure is much debated.
Thin diamond crystals - the doorway to new diamond physicsStaff : SH Connell, JPF Sellschop, E Sideras-Haddad.Students : BP Doyle, IZ Machi, RD Maclear, DB RebuliCollaborators :P Aggerholm (Aarhus), M Rebak (DeBeers), J.E. Butler (NRL-Washington)
If thin, that is to say micron and sub-micron thickness, diamond of high quality, were to become available it would make possible a large suite of research opportunities in both atomic and nuclear physics, as we have long appreciated. Conventional polishing techniques become problematic for thicknesses below 20 microns, owing to increasing difficulties with plastic deformation of the diamond remnant. We have made substantial progress in this quest through a new approach : carbon ions are implanted into a prepared diamond at an energy selected to place the Bragg peak at a depth below surface corresponding to the thickness of the final diamond sliver required. A dose of incident ions is delivered that is adequate to amorphise the layer corresponding to the Bragg peak. The diamond is then heated to about 1200C to both make the amorphisation more complete and to restore
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the crystal perfection of the superficial layer of any small amount of radiation damage by annealing. This is followed by an electrochemical etch in pure water whereby the amorphous layer is removed, allowing the superficial layer to float free. Special techniques are necessary to handle the sub-micron to few-micron thick diamonds. In this manner we have successfully prepared diamond targets of 1 to 3 microns thickness.
Some of the new suite of research possibilities enabled by these exciting samples involves applying any of Ion Beam Analysis (IBA) measurement technologies in channeling mode. This delivers lattice structural information about defects and impurities, in addition to the normal analytical information. Channeling Rutherford Backscattering Spectroscopy is used to study the details of the thin crystal production process and to optimise it. Channelling-ERDA has been applied to identify hydrogen structures in diamond. Transmission Channeling Forward Scattering is being used to study oxygen termination structures on diamond.
A new concept in creating thin single crystal samples will shortly be explored in which the implanted ion species is helium and the superficial layer is removed by the application of heat alone, as successfully demonstrated in the case of silicon.
Hydrogen dynamics and chemistry by micro-scanned Elastic Recoil Detection AnalysisStaff : SH Connell, JPF Sellschop, E Sideras-Haddad.Students : BP Doyle, CG Fischer, IZ Machi, RD Maclear, RWN Nilen, DB RebuliCollaborators :P Aggerholm (Aarhus) K Bharuth-Ram (UDW), JE Butler (NRL-Washington), E
Fritsch (Institut de Matériaux de Nantes)
Diamond has many physical and chemical properties attractive to the semi-conductor industry. The presence of hydrogen in the diamond lattice influences these properties. Its presence is known to affect the hardness of the material, it passivates active dopants and changes the optical transmission of diamond. Theoretically, hydrogen is a simple example of an atom in a covalently bonded macro-molecule, and is therefore instructive to model. The unique capability to perform 3-dimensional microscopy of trace hydrogen distributions has been developed at the EN-Tandem accelerator to a level of sophistication unmatched elsewhere in the world. This has enabled a coherent program focusing on hydrogen dynamics and chemistry in diamond, supported as well by the other projects using muons, positrons and radioactive ions described above. The new method has been called ERDA (see the title of this section for expansion). In one programme of measurements, phenomena like hydrogen stability, diffusion, trapping, detrapping, decoration, complexation and so on are studied. In another set, hydrogen distributions were evaluated to characterise natural and synthetic processes leading to hydrogen incorporation into diamond. This has relevance to metastable synthesis of diamond as well as the natural genesis environment of diamond. This program has recently been extended to include the channeling phenomenon, due to the availability of thin single crystal diamond, as described in the previous research project. Channeling-ERDA measurements will give a much improved picture of the crystallographic location of hydrogen in diamond. The possibility of measuring the exact location of the hydrogen allows measurements of other important phenomena involving hydrogen in the diamond lattice, for example, hydrogen diffusion pathways and complexation modes with other defects.
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European synchrotron radiation facility (Grenoble)Staff : JPF Sellschop, M RebakCollaborators :A Freund (ESRF)
Work over the past few years has continued in pursuit of using diamond in critically sensitive areas in this powerful third generation radiation source. Diamond is usually compared with silicon and germanium in its application as a monochromator for synchrotron radiation. Some of the physical constants for which diamond is greatly superior to the other two are the linear absorption coefficient (and consequently the absorption length) for, say, 8 keV X-rays
diamond is enormously transparent for these wavelengths the Debye temperature for diamond is very high, and consequently the thermal vibration
amplitude is very low indeed the thermal expansion coefficient is very low the heat conductivity is very high the Darwin band width is smallThe usually accepted figure of merit in such applications for diamond is some 600 times superior to silicon, and 2000 times better than germanium. With the deployment of especially-grown diamond with very small mosaic spread, tests have been carried out on the use of diamond as a high heat load monochromator. Rocking curves confirmed the high quality of the diamond materials selected. In heat load tests the rocking curve width remained constant over a wide range of beam intensities, quite unlike silicon. The highest intensity, namely 3.5 kW / mm2, tested is to put it mildly most impressive, since it corresponds to an energy density that exceeds that at the surface of the Sun !Diamond proves to be radiation hard in this application also with very little evidence of damage over prolonged periods of beam exposure. A second research thrust has been in an attempt to bend diamond to provide saggital focusing of the monochromatised x-ray beam. A crystal bender was especially designed, a diamond of high quality was configured to dimensions 10 mm x 5 mm x 67 micrometer with the large face the {111} orientation. This diamond was successfully and repeatedly bent to a radius of curvature of 0.9 meter, giving a demagnification (focusing) factor of 20 times ! This field has proved to be a fruitful one and will be continued. Two invited papers were presented at the recent SPIE conference in San Diego (July 1998).
Coherent, correlated phenomena resulting from the Incidence of High Energy Leptons and Photons on Oriented CrystalsStaff : SH Connell, JPF Sellschop.Students : ZZ VilakaziCollaborators :K Kirsebom (ISA-Århus), R. Medenwaldt (ISA-Århus), U. Mikkelsen (ISA-Århus), SP
Møller (ISA-Århus), E Uggerhøj (ISA-Århus), T Worm (ISA-Århus), S Ballestrero (INFN-Florence), P Sona (INFN-Florence), K Elsener (CERN), YuV Kononets (RRC Khurtarchov Institute), A Apyan (Yerevan Physics Institute), RO Avakian (Yerevan Physics Institute), AE Avetisian (Yerevan Physics Institute), KA Ispiyran (Yerevan Physics Institute), C Biino (INFN-Turin)
The Research programme is founded predominantly in fundamental Physics, embracing both the local and the overseas capacity in a ordinated way. The scope of the research addresses all phenomena associated with lepton-photon processes resulting from the incidence of ultra-relativistic particles on highly-ordered crystalline materials. Scattering in a well aligned crystal geometry is extended to investigate coherent and correlated versions of the basic theory of electromagnetic processes viz. quantum electrodynamics (QED) at higher energies. QED is a highly developed field theory and has been investigated experimentally to very stringent detail. In recent years it has become technically possible to investigate QED processes in very strong crystalline electromagnetic fields. In short, new
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phenomena and physics do arise, opening up a plethora of new concepts to be explored therein inter alia Strong Field QED. This programme is undertaken at the CERN-SPS in the multi-national NA43 collaboration. The results show either very strong enhancements or losses in the cross-sections, as well as changes in the shape of the cross-sections. This in turn leads to new phenomena, which deepen an understanding of fundamental theories, as well as allowing new theoretical tests and new applications. The NA43 experiment has essentially completed its brief. The investigations which were carried out throughout the period that covered most of the period reported herein are: Establishing and studying the occurrence of a very new effect, the production of linearly polarised, partially monochromatic ultra-hard single photons by electron aligned incidence on crystals of very specific relative orientation to the beam. Studying coherent enhancements in both pair-production and brehmsstrahlung at ultra-relativistic energies. Realising and studying for the time in the laboratory under well characterised conditions the occurrence of super-critical fields and their effect on energy loss mechanisms. Studying channeling in bent crystals for super-relativistic particles. Most of these new phenomena have lead to remarkable new devices which have already found application in other High Energy Physics experiments, or are in a proposal stage which may lead to new HEP capabilities. Of special mention : One new proposal is intended to lead to the use of the ultra-high energy (polarised) photons produced as described above as a tool to study the gluon contribution to nucleon spin. Another proposal would like to extract parasitic beam from the LHC accelerator for fixed target experiments using bent diamonds.
Apart from the good physics delivered by the CERN programme, there has also been significant technology transfer. The Physics Analysis Workstation (PAW) package was ported to a graphical Linux-PC environment by S Ballestrero during a working visit of his to the SRCNS. This was the time the entire CERN Libraries became available on PC in a graphical environment. Previously, only mainframes or mini-computers could access the physics capability of this software. The port was welcomed by the international (HEP) group and the CERNLIB's on Linux-PC's became officially supported by the CERN Computer Group from then mn. S Ballestrero also developed a Data Acquisition System (DAQ) that front-ends PAW to small lab detector systems. This gave the SRCNS (and any other small lab) essentially the same data capture power as the large CERN experiments for an incredibly reduced price. This innovation has been released via a WW page, and other labs are now sharing in it. This development has allowed us to run the CERN Monte Carlo package GEANT (which simulates many physics processes from keV to TeV interaction energies) and to contribute effectively to the analysis of data taken at CERN in our own local environment, by having a local PAW capability. It also enabled us to take the lead internationally in certain of our Physics Experiments based locally at our microprobe. Part of this programme is discussed in a separate section.
The Physics foothold at CERN will be extended when the ex-PhD student ZZ Vilakazi takes up a Post Doc position on four CERN-HEP experiments later this year. An initiative to synergise our efforts with the local theoreticians and other interested groups in other Universities in the country is in progress.
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Alkali Halide Materials and Super-Ionic ConductorsStaff : DJ Comins, SH Connell, TE Derry, JPF Sellschop.Students : CG Fischer, RWN Nilen
Collaborators : EJ Sendezera (U Zululand), AT Davidson (U Zululand)
The use of positrons as a microscopic probe for the investigation of defects in crystal and amorphous systems, allows a study of the kinetics of creation and annealing out of defects. In particular, for the Super-Ionic materials, an enhanced conductivity mechanism occurs which is not yet fully understood, and is an issue of great current importance. An experiment using Positron Spectroscopy is being developed as it is believed it can provide information on the role of vacancies in this phenomenon.
Non-Stochastic Ion-Implantation - Industrial Collaborative R&DStaff : SH Connell, JPF Sellschop.Collaborators : W Wesch (Jena), Leonard C. Feldman (Nashville)
The aim is to develop and study non-stochastic systems for maskless implantation of dopants for situations of small feature size (<500 nm) and a large degree of integration (1x109 devices per chip). The possibility of dopant implantation via shape pre-programmed raster scanning with highly focused ion beams has already been postulated. We are exploring a non-stochastic method for maskless implantation to improve device integrity.
The COLLECT Data Acquisition SystemStaff : SH ConnellStudents : BP Doyle, IZ Machi, RD MaclearCollaborators : S. Ballestrero (INFN-Florence)
COLLECT is a powerful multi-parameter data acquisition (DAQ) system, running on a Linux PC. It was developed in order to serve the ever more complex data sets that are being taken at the SRCNS. COLLECT front-ends to the Physics Analysis Workstation (PAW/PAW++), a powerful data manipulation/visualisation tool, developed at CERN. The PAW system can be used as an online presenter as well as for offline replay of the data. COLLECT therefore delivers the computing power in DAQ previously known only on powerful computers at major high energy physics facilities to a PC and CAMAC based system affordable by a small lab. COLLECT can be easily configured to any desired experiment. Work is being done on a GUI version with a more easily configured CAMAC event cycle and data n-tuple. This project was jointly funded by The University of the Witwatersrand and The University of Durban Westville in South Africa. The system was published via the web, and has been attracted much interest. For example, we recently received a request for it from CALTECH. It has laid the foundation for a new generation of experiments at Schonland. For example, it enabled the event reconstruction that allowed us to do micro-scanned imaging of trace hydrogen distributions in diamond (discussed above). This capability attracted a director of an American Lab to do a 6 month sabbatical at Schonland, which in turn led to additional foreign funding of the project by nearly R100 000.00. This is one of the technology transfers enabled by the CERN research programme (discussed above).
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The Schonland EN-Tandem Accelerator Control SystemStaff : AH Andeweg, JUM Beer, SH Connell, K Coone, E Rood JPF Sellschop, E Sideras-
Haddad.Students : RD MaclearCollaborators : P Aggerholm (Aarhus), M Hogan (NAC), F Weehuizen (NAC)
Currently the 6MV EN-Tandem of the Accelerator Laboratory at the Schonland Research Centre for Nuclear sciences is being upgraded for control via a Graphical User Interface (GUI) computer system. The system is based on distributed network control via an OS/2 network messaging system. Control of the electronic equipment is done over a RS-232/RS-485 link to digital and analogue control modules. The benefits of a computer controlled accelerator include: better quality ion beam; faster set-up time; decreased operator reliance; increased accessibility to outside users; introduction of intelligent control algorithms; automation of routine procedures; and upgrade of all power supplies. The control program has the properties of using a high degree of commercially manufactured software; is highly modular; based on object oriented programming code; is network based using distributed intelligence; is highly customisable; exploits the messaging, prioritising, queuing and resource sharing of the OS/2 operating system; and can be sequentially phased in with no major equipment down-time. All the current power supplies will be replaced with modern, stable power supplies. Control of the power supplies will be done using harsh environment capable ADAM/NUDAM modules on a RS-485 drop-down network. The modules are extremely stable and highly modular with only 3 types of modules needed to control all power supplies (analogue output, analogue input and digital input/output). Voltage ramping of power supplies is built into the modules and no extra code is needed for this. The modules connect directly to the RS-232 port of a PC and no complicated interfaces or drivers are needed. The network messaging system, or Variable Table, is used to broadcast instructions to the various power supplies. The table contains reference and actual values for every control object in the network. The GUI console program updates the variable table when a user wishes to change the value of a power supply. Notification queues notify clients (control applications running on equipment-local computers) when a value in the table and changed, and the required action is taken by the clients. Clients update the variable table when a value is read from a power supply, and the GUI displays these values to the user. A relational SQL database is used for storing all the information about the control system. The database is accessed by the variable table, clients and user console at startup to retrieve this information. Based on this information, various power supplies can be controlled in a predefined manner. The database also defines how the user interface behaves and appears to the user. Expanding or modifying the system to include more control objects or differently configured control objects is simply a matter of editing the database, not the software.
Most of the systems software concepts have been developed at the National Accelerator Centre. Its implementation at Schonland has been modified to further distribute intelligence in control operations, display a higher reliance on cheaper modular commercial components and a greater reliance on the GUI for the User interface. The design and implementation of the client programs, the console program, the installation of the NAC-developed Variable Table, and the installation of the commercial database and networking software has been part of the MSc and PhD program of the student. The control electronics, cabling and cabinetry were developed by the technical staff.
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Generic client control applications for the objects controlling Analogue input, output and digital input/output have been written for these basic types of operations on power supplies modules. These generic objects are resource file customised via the database to create a control application for any given power supply, with no further programming (only editing of the accelerator database). The server application accessed by these clients for communication with all the control modules belonging to a single node via the COM port of a PC has been written. Instructions are passed to the server via a prioritised queue, and extracted to the modules according to their priority in the queue. A Mark I user interface has been written for testing the control of power supplies via the multiple-clients-server system. All control electronics and new / modified stabilised power-supply implementations for the hardware component of the control of the Duoplasmatron, the gas ion source of the accelerator facility, have been completed. The Full Duoplasmatron electronics is therefore mounted into a single rack and equipped with dummy loads, and connected to the node computer. This system has been fully tested on the complete Duoplasmatron electronics rack using a standalone node computer. All conceivable faults have been simulated, and the exception handling and error recovery have functioned as planned. The speed of the system under load conforms to design specifications. We are therefore ready to install the control node and electronics. Following a test and evaluation period under running conditions, we will proceed sequentially to implement the entire 6-node control system. Subsequent control nodes will be replications of this control node, customised by extending the accelerator database. In preparation for this, the network-wide variable table communication program has also been installed and is running over the OS/2 sub-network using NetBIOS. Network-aware database access has been established and implemented into the clients. The new control console cabinetry has been designed and constructed and is currently being equipped with the hardwired segment of the control-system (fast-safety systems, analogue feedback systems etc). We expect to be operating with the control node later this year. We are investigating industrial interest in this control system.
Heavy-ion Nuclear Reaction MechanismsStaff : SH Connell, JPF Sellschop.Students : TG StevensCollaborators :V Allori (Milano), C Birattari (Milano), M Bonardi (Milano), M Cavinato (Milano), F
Cerutti (Milano), A Di Filippo (Milano), E Fabrici (Milano), E Gadioli (Milano), E Gadioli Erba (Milano), SV Fortsch (NAC), JJ Lawrie (NAC), SJ Mills (NAC), FM Nortier (NAC), I Schroeder (NAC), GF Steyn (NAC), AA Cowley (Stellenbosch).
Since January of 1993 this collaboration has been involved in a comprehensive study aimed at a better understanding of the important mechanisms of heavy ion reactions and de-excitation in processes initiated by projectile energies between the coulomb barrier and the fission threshold. A starting point has been the concepts derived from the study of light particle induced reactions. These have been extended with modification, as well as with the introduction of new concepts, to heavy ion induced reactions. Experimentally we have studied the interaction of 16O and 12C, incident on the medium mass, mono-isotopic 103Rh. We have adopted and developed the powerful activation technique to obtain the comprehensive data set necessary to rigorously test the theoretical interpretation of these reactions as developed by a group at the University of Milan. More than thirty reactions representing excitation functions, angular distributions and residue recoil energy distributions over the entire energy discussed above have been accumulated. In addition, this data set is accurate in absolute terms to 20%. The uniform theoretical framework that has been gradually developed, is now capable of describing the data to a remarkable degree. The processes of excitation described by a mean-field approach, is considered separately to that of de-excitation where a time stepped Monte Carlo analysis
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based on the Boltzman Master Equations is used. The matching of the theory to the data did not proceed via adjustment of free parameters, but rather via careful selection of the major reaction and de-excitation mechanisms. Finally we could conclude that the major reaction mechanisms include only complete fusion, partial fusion of alpha like components, and proton and neutron transfer. The de-excitation requires pre-equilibrium emission to be considered over the whole energy range as well as ultimately statistical emission from the equilibrated nucleus. The mean field energy evolution could be established.
The latest and most striking results of these experiments and the subsequent theoretical interpretation demanding our current attention in the next beam-times, is the investigation of a novel de-excitation mechanism revealed by our research. This relates to the fast re-emission of alpha-like fragments, after very few nuclear interactions. This process has been found to be distinct from break-up and also pre-equilibrium emission. Following the incomplete fusion of an particle or two loosely bound ,s in the form of a 8Be, the re-emission of a fusing particle with a large fraction of its initial energy, is very important. In fact the probability of this phenomenon is even greater than that observed in particle induced reactions since these incomplete fusion processes occur in a low density, peripheral region of the target nucleus. Consequently, as these incomplete fusion processes become more important with increasing projectile energy, we find with increasing 12C energy an increasingly high number of low energy equilibrated nuclei with mass and charge close to that of the target. Their further decay via evaporation leads to the dominant formation of near target nuclei.
Following the success of these earlier measurements, subsequent experiments have been proposed to and enthusiastically received by the Physics Advisory Comittee (PAC) of the National Accelerator Centre. These proposals included the measurement of particles emitted in the interaction of 12C with 93Nb (PR27a) and the spectra of projectile fragments emitted in the interaction of 12C and 16O with 93Nb (Pr32a). Each of these measurements were successfully completed and this data is currently in the process of being analysed and compared to the theoretical interpretation. In addition to these measurements, we have proposed setting up a new new Recoil Particle Spectrometer (RPS) facility using silicon microstrip detectors, in order to measure 8Be inclusive spectra in the bombardment of a 93Nb target with 12C beams, detecting the unbound 8Be as two breakup particles in coincidence. This facility is currently in an advanced stage of preparation and we expect to begin testing in September of 1998 followed by measurements in the early part of 1999. The work has led to many publications and conference presentations.
Inter-disciplinary Research, Industrial Collaborations, Service Analysis using the Ion Micro-Beam FacilityStaff : AH Andeweg, JUM Beer, SH Connell, K Coone, RJ Hart, E Rood JPF Sellschop, E
Sideras-Haddad.Students : BP Doyle, CG Fischer, IZ Machi, RD Maclear, DB Rebuli, TG Stevens, ZZ VilakaziCollaborators :P Aggerholm (Aarhus) K Bharuth-Ram (UDW), JE Butler (NRL-Washington),
E Sendezera (University of Zululand), MHB Breese (SPM Unit, Oxford) G Bench (Lawrence Livermore National Laboratory), A Antolak and D Morse (Sandia National Laboratory).
The 6MV Tandem accelerator and the 2.5MV single ended POTCH accelerator provide the beams which are used by the Micro-Scanning Ion Beam Analysis Facility (Figure 1). These beams can be focused to micron or in some cases to submicron dimensions, and rastered over the sample, where
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“fingerprint” radiation from some kind of physics phenomena is excited, labelling the elements in the sample. The analysis is also a (trace level) quantitative microscopy. The computer acquisition system can correlate the beam scan position and the amount of “fingerprint” radiation with pixel colour levels in a visual image. The current quantitative microscopies available at the facility are :
-PIXE Proton Induced X-ray Emission : Quantitative analysis and mapping of heavy elements (Z 13) with as low as 1 ppm sensitivity. The probed volume is from surface to about 30 m. The microscopy is based on the fluorescence of atomic X-rays by the interaction of the beam of protons or heavier projectiles on the sample.
-STIM Scanned Transmission Ion Beam Microscopy : Quantitative 3-Dimensional mapping of the sample density using Computed Tomographic Reconstruction. This microscopy is based on the energy loss of beam traversing thin samples ( < 50 m)
-RBS Rutherford Back Scattering : Quantitative analysis and mapping of elements heavier than the matrix. Depth dependence from surface to 10 m is resolved and measurements on a microscanning mode enable 3-D imaging. This microscopy is based on simple kinematics models and makes use of reliable software analysis packages.
-NRA Nuclear Reaction Analysis : Quantitative analysis and mapping of some elements (B, F, N, O etc) down to few tens ppm levels. This microscopy is based on nuclear reactions between the beam and selected elements in the sample.
-ERDA Elastic Recoil Detection Analysis : 3-D quantitative analysis and mapping of very light elements. This microscopy is based on simple kinematics and is particularly suitable for hydrogen analyses. Current detection limits are around 100 ppm.
-Channelingin conjunction with PIXE, ERDA, NRA and RBS: This microscopy enables lattice locations of elements to be determined, suppression of matrix element signals and evaluation of lattice integrity. This microscopy exploits the crystalline structure of the matrix.
-SecEM Secondary Electron Microscopy : Mapping of surface morphology. This microscopy is based on collection and analysis of secondary electrons ejected out of the sample by the beam.
The nuclear microprobe facility is currently used in research applications which cover the fields of geosciences, metallurgy, earth sciences, environmental studies, paleoclimatic research, biology and biomedicine. In addition there are projects in the field of nuclear-solid state research and particularly in studies of diamond physics. New analytical methodology has been established, which is based on ion-solid interactions and is applied in impurity studies in diamond as well as hydrogen and oxygen diffusion.
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Development of Accelerator Mass Spectrometry for Ultra-trace and dating studies in Interdisciplinary Research Staff : AH Andeweg, JUM Beer, SH Connell, K Coone, RJ Hart, E Rood JPF Sellschop, E
Sideras-Haddad.Collaborators :P Aggerholm (Aarhus), T. Brown (Lawrence Livermore National Laboratory), J
Southon (Lawrence Livermore National Laboratory), S Freeman (Lawrence Livermore National Laboratory), J Butler (Naval Research Laboratory), S Sie (CSIRO, Australia)
Modern AMS is a new state-of-the-art technology for ultra-trace and dating studies in interdisciplinary sciences. It is highly fundable as well as very marketable. Its target User group find it easier to comprehend than other nuclear science based interdisciplinary technologies. In addition the potential User group also contains large industrial concerns. Development of the WITS-Northern Accelerator Facility to the level of AMS capability is one of the key features of a long term plan to stabilise the funding and upgrade the performance of the Tandem Accelerator. AMS is an exceptionally efficient use of beam-time, and is accommodated very well along with other research programmes on the same facility. Besides providing excellent new interdisciplinary research opportunities, it is expected that the project will benefit all the research based at the accelerator, as it will provide the funding to upgrade the facility and acquire further staff.
While conventional mass spectrometry techniques, such as SIMS, ICP-MS and SRIMP, and decay counting are efficient for determining isotopic ratios as low as 10 -9 in microgram to nanogram samples, they cannot detect efficiently long-lived isotopes (mean lives from tens to million of years), especially with isotopic ratios as low as 10-9 to 10-15. An additional problem in ultrasensitive mass spectrometry measurements is that the rare isotope signal is very small as compared to those of interfering atoms and molecules with very similar masses, which are impossible to be filtered out. It is in this ultra sensitive regime with long lived radioisotopes that Accelerator Mass Spectroscopy or briefly AMS, came to play a very important role with some unpredictable revolutionary applications, especially in the field of biomedicine. The extracted ions, in the form of a negative beam, are accelerated to high kinetic energies by a positive electric field of some million volts in a nuclear electrostatic accelerator. In the centre of the accelerator, a cell containing a small volume of gas or a thin carbon foil is located. The accelerated incoming ions undergo collisions, losing one or more electrons and become positive ions exhibiting a range of charge states. In this way, all molecular species dissociate and cannot interfere with the isotope of interest any more. However, atomic isobaric interference still remain. To completely resolve these, the isotopes have their mass, energy, velocity and charge determined by standard nuclear physics instrumentation techniques. This is possible because of the high energy of the ion-beam. The result is an AMS instrument with a sensitivity typically six orders of magnitude greater than that of conventional mass spectrometry techniques.
The User base is being canvassed. Applications to external funding sources are in progress. Support from National and International institutes is currently being negotiated. A pilot project is being supported using outside funds. The initial design for the system is also in progress. At this stage the response from potential users and funders, as well as the support from various national and international institutions is very encouraging. The Vice president of the CSIR has fully supported the planned development and has taken a leadership role in promoting it as well as forming a development partnership whereby CSIR sample preparation facilities and recognised expertise will form part of the final joint facility. The international community has also been extremely enthusiastic, and more than three tons of very sophisticated equipment has been donated by various foreign AMS
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laboratories. The combined value of this equipment, some of which has already arrived, is over $500 000.00. The CSIR have funded the shipment costs. The progress in computerisation of the current facility is proceeding very well, and has already been discussed. The market survey and business plan generation components are also currently underway.
A brief mention of topics to be addressed follows : Research in Global and Regional Climate Change Characterisation of atmospheric pollution in terms of anthropogenic activities Characterisation of Regional Groundwater Systems Anthropology, History and Preservation Technology AMS in Biomedical Dosimetry Applications of AMS in Geosciences and Isotope Geology Ultra-Trace Elemental Analysis Isotope-Geochronometry and Tracers
These topics have been given more detailed profile elsewhere.
Projects in (Nuclear) GeologyStaff : RJ HartStudents :Collaborators :SH Connell (WITS), E SIderas-Haddad (WITS), JPF Sellschop (WITS), M Tredoux, M
de Wit (UCT), R. Hargraves and M. Cloete (Council for Geoscience) DG Pearson (Dept of Terrestrial Magnetism, Carnegie Institution of Washington), M Cloete and M Drury (Utrecht), D Moser (Royal Ontario Museum), E Eida (Norwegian Geological Survey), M. Rebak (de Beers)
Sulphide Inclusions in DiamondProton-induced X-ray emission (micro-PIXE) and instrumental neutron activation analysis (INAA) methods are used to obtain information about the platinum-group elements (PGE; Pt, Pd, Rh, Ru, Os, and Ir), and sometimes Au and Re also, in microscopic sulphide inclusions from diamonds. Samples of known paragenesis have to be selected. The research project is long term aimed at mantle PGE chemistry as well as the genesis mechanisms of diamond.
A study of the magnetic anomaly near the centre of the Vredefort structure Ongoing research on the Vredefort structure has been conducted by our group for many years. Current active areas are the following :-a) Transmission Electron Microscope work on the orientation of magnetic minerals in relation to
shock deformation features in quartz.b) Atomic magnetic force analyses on magnetic thin sections in order to determine the source of
high remanence in the rocks from the Vredefort basement.
Regional geology - Investigation of the Morokweng structureThe Morokweng structure, located in the North West province of South Africa, stands out clearly on the regional aeromagnetic map of southern Africa as a ~70 km diameter circular feature made up of concentric magnetic anomalies. The region is almost entirely covered by post-Cretaceous Kalahari beds, and interpretation of the subsurface stratigraphy beneath the Kalahari sands relies on the scant outcrop, chips from geohydrological boreholes and geophysical data. The rocks beneath the Kalahari cover consist largely of Archaean granites and rocks of the Kraaipan Group, composed of banded
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ironstones, meta-volcanics and minor ultramafics. Away from the structure to the south and west the crystalline basement rocks are overlain by gently dipping Proterozoic sediments. The circular structure was initially interpreted as an igneous intrusion. However, the superficial similarity of the aeromagnetic signature to other known impact sites and the identification of planar deformation features (PDFs) and other shock deformation phenomena found in surface pebbles and in rocks recovered from boreholes. has led to the reinterpretation of the feature as an impact structure. This study includes the following.a) Proton probe analyses of Platinum rich phases recovered from boreholes.b) U-Pb analyses of zircons recovered from a postulated impact melt.c) Ar-Ar analysis of biotites recovered from a postulated impact melt sheetOrigin of the quartz noriteThe quartz norite is an unusual lithology in the context of regional geology of the western Kaapvaal craton. It is more basic than the underlying basement granites, yet it contains more quartz than typical mafic and ultramafic rocks of the Kraaipan group. Although the mineralogy and textures of the quartz norite superficially resemble those of plutonic rocks such as silica-rich norites or rocks of charnocitic affinity, they have concentrations of some siderophile and chalcophile elements more characteristic of mafic or even ultramafic rocks such as basalts or peridotites. Similarly, the Ni-rich phases (e.g. liebenburgite and the Ni-oxides) hosted by the quartz norite are exceptionally rare. The origin of the quartz norite is uncertain however, the shape of the body (the absence of any discernible roots) the chilled basal margin and the evidence for shock metamorphism in the basement, has led to the conclusion that these rocks represent an impact melt sheet. Both the clear, undeformed, prismatic zircons, and the primary biotites exhibit the morphology of minerals that crystallised from a magma. These minerals provide indistinguishable ages using two different dating systems and we interpret this circa 145 Ma age as the time of crystallisation of an impact melt. In view of recent speculation that meteorite impacts could cause flood basalts and major rifting events, the late Jurassic age for the Morokweng impact is very interesting, because this period is generally considered to be a time of accelerated global geological activity. This is especially true in the southern hemisphere, where this time period coincides with the break-up of the Gondwana super continent. In the context of the dramatic geological activity at the time, it is interesting to note that the Jurassic–Cretaceous (J–K) extinction event is listed by Raup and Sepkoski (1986) as one of the eight major episodes. The exact nature of this extinction and its absolute age are both still a matter of keen debate:
International collaborative study on Cretaceous -Tertiary (K-T) boundary samples recovered from the ocean floor The objective is to analyse samples from Leg 165 from a trans-Atlantic traverse, as well as K/T sections on land in Mexico and Belize will be analysed for ultra-low level Ir concentrations.This is a new international collaboration on the nature of the ocean floor deposits of the Cretaceous-Tertiary (K/T) boundary. The purpose of this project is too analyse ocean floor deposits associated with the K/T boundary for Ir, thought to be indicative of an impact event. The section comes from a deposit about 1500 km from the Chicxulub crater, the proposed impact site for the K-T extinction event. The section has a well developed tectite layer, in which we found shocked quartz. There are limestones of varying descriptions either side.
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Accelerator Facility Equipment Inventory
1 6 MV EN-Tandem Van de Graaff accelerator with 8 beamlinesa) Neutron activation + remote measurement facilityb) Neutron radiography line
c) Quantitative analytical Heavy-Ion Microprobed) Nuclear-Solid State Physics TDPAD facility
e) High Energy Heavy-Ion Implantation Facilityf) PIXE analysis of Environmental Aerosolsg) Pure Nuclear Physics Experimentsh) Oxygen and Nitrogen analysis
2. 2.5 MV Van de Graaff acceleratora) Dual injector to the Ion-Microprobe (high resolution analytical microscopy)
3. Off-line counting systemsa) gamma spectroscopyb) positron spectroscopy
4. Nuclear data processing instrumentation a) +/- 500 pulse processing modules
5. Computerised Data Acquisitiona) CAMAC based Physics Analysis Workstation (PAW ex CERN)b) OMDAQ dedicated to Microprobe projectsc) The GeniePC Spectroscopy Suite for singles measurements
6. Tandem Peer-to-Peer LAN (Unix, OS/2, W95 lab services cluster)a) WWW server
b) FTP, Program and file Serverc) CDROM burnerd) DAQ workstationse) Analysis workstations
7 Neutron Activation Analysis Facilitya) sample preparationb) automated sample changerc) gamma spectroscopy d) on-line Analysis System
Accelerator Facility Status Report1. 6 MV EN-Tandem Van de Graaff accelerator with 8 beamlines
Excellent performance with all beams. In particular, the accelerator has operated near its design voltage with heavy-ion beams at high charge states and currents with impressive stability, reliability and requiring very little operator intervention. This is attributed to :a) the husbanding of the new tubes, belt and column resistors installed a few years agob) the new management culture with a unified technical vision and upgrading during
repairs and developmentsc) better vacuum practice as allowed by increased running cost allocationsd) new skills (eg sabbatical of P Aggerholm (Denmark) and acquisition of E Rood)
The beam-lines and target stations currently in use are in good working order, and some have received major development as part of the implementation of new projects.
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2. 2.5 MV Van de Graaff acceleratorInstallation as dual injector to the Ion-Microprobe for high resolution analytical microscopy is complete. There has been both H and He beams into the chamber of impressive brightness and stability. However operation continues to be unreliable. The HV platform electronics, vacuum and gas supply equipment have now all been overhauled or replaced. Recent air tests are now delivering reliable operation, and tests under pressure are in progress. The EN-Tandem has had to carry all the Ion-Microprobe projects during this period, and this has been very strenuous. However, we have every expectation that the “Potch” machine will soon be operational. It is supposed to have a legendary reliability and require very low overheads in its operation. It is intended to be deployed for the routine proton-Microprobe work at very high spatial resolutions and rapid turn-around times.
3. Off-line counting systemsThese are state-of the art systems and in good operating order and regularly used. Accreditation by the CNS for IGP purposes is in progress.
4. Nuclear data processing instrumentation These are state-of the art systems and in good operating order and regularly used.
5. Computerised Data AcquisitionThese are state-of-the-art systems and in good operating order and regularly used. The COLLECT DAQ system is an innovation, discussed above.
6. Tandem Peer-to-Peer LAN (Unix, OS/2, W95 lab services cluster)Most of the facilities still represent high-end computers, due to the upgrade following the theft of 11 computers from the laboratory in early 1996. In some cases finances for further upgrades have been applied for.
7. Neutron Activation Analysis FacilityAs part of the restructuring of the Schonland, the NAA facility was recently relocated to the old Neutrino Surface Station Laboratory. This has resulted in a cleaner and redesigned installation, in a very low background environment. The DAQ software server is currently being upgraded. This system is in continual use.
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PIXE Detector
RBS Detector
X Rays
BackscatteredbeamRBS
SEM Detector
Secondaryelectron
emission (SEM)NRA Detector
ERDA Detector
Optical / CCD
Forwardscatteredlight ions
Transmitted H.I.beam
Nuclear reactionproducts
Ion Beam Microbeam1-10 m
Focussingquadrupole
magnets
Analysing Magnet
Switcher Magnet
6 MV EN Tandem Accelerator
2.5 MVVan de Graaff
Accelerator
Microprobeend station
Quadrupoledoublet
Cooledprotection
slits
90 degreebending magnet Analyser
slits
Object slits
Post Acceleration Stripper
6.8 m
Pneumaticvalve
Collimator slits
Analyser slits
Object Slits
ObjectSlits
Schematic representation of the Accelerator Laboratory, showing mainly the Ion-Microprobe Facility. The inset is a schematic diagram of the focused ion-beam exciting radiation from a sample, leading to various (trace) quantitative microscopies. The other 7 available beamlines are shown schematically and truncated.
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Usage of the Accelerator Laboratory (1997-1998 2-year average)
Project Group Proposers Percentage
Many projects under the programme:
ERDA for H in Diamond
Particle-Solid Interactions SH Connell, BP Doyle, IZ Machi, RD Maclear JPF Selschop E Sideras-Haddad all WITS-Physics
JE Butler NRL-Washington
25%
Many projects under the programme:
PIXE analysis of time dependent aerosol streaker samples
Environmental Aerosols HJ Annegarn, SJ Piketh, S Meter, P Formenti
WITS-Physics, WITS Climatology
20%
Many projects using the Ion-Microprobe
Council for Geosciences
Atomic Energy Corporation
BOART hard materials
SA Inst of Med. Res.
Anglo American Res Labs
Inst Mineralogie - Hannover
Development, Calibration
D De Bruyn
M Andreoli
S Luyckx : WITS-Metallurgy
S Lee
C Smith
A Wittenberg
SH Connell, E Sideras-Haddad
20%
Neutron Radiagraphy Applied Neutron Physics JIW Watterson WITS-Physics 5%
Neutron Activation Applied Neutron Physics JIW Watterson WITS-Physics 5%
Many projects under the programme:
High Energy Heavy-Ion Implantation
Lattice effects in II damage propagation
HEHI in Semi-conductors
HEHI in Alkali Halides
HEHI in thin films
Thin Diamond production
CG Fischer WITS-Physics
S Goodman : UPretoria-Physics
A Davidson : UZululand-Physics
M Maaza : WITS-Physics
JPF Sellschop : WITS-Physics
5%
Scheduled maintenance AH Andeweg, JUM Beer, E Rood 10%
Unscheduled 10%
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SchonLAN Computer facilities
LAN Supervisor : BP Doyle
LAN Assistant Supervisor : RD Maclear
Computer Representative : SH Connell
Electronics : AH Andeweg, K Cooney
The computer facilities at the SRCNS can be divided into two major sections: the SchonLAN Novell server and the workstations which connect to it, and the UNIX network. There are also a few off-line PCs (mainly used for data acquisition).
The SchonLAN Novell Network
The SchonLAN network runs under Novell 4.11 and has about 75 users. The majority of people at the SRCNS use this network for their printing, applications and e-mail needs. The server itself is a Pentium 100 with 64MB RAM, 5GB of hard drive space, a DAT 2 tape drive and a CD-ROM (all SCSI). The physical cabling system is 10MB 10 Base-T. This machine is also a file server for shared data and certain applications (MS-Office, user ed applications etc.).
UNIX (LINUX) Network
Over the last few years there has been a rapid development of a UNIX network at the SRCNS. This has mainly been due to the powerful data acquisition and manipulation software that has become available. The network consists of 8 PCs running Linux. This network utilises the same cabling system as the SchonLAN. This network hosts the WWW servers, FTP servers, amongst other specialised servers for Unix environments.
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Publications (1998-99)
1) DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JE Butler, JPF SellschopOxygen surface studies in ultra-thin diamonds using transmission channeled Rutherford Forward ScatteringNucl. Instr. & Meth. in Phys. Res. 158 (1999), 701-705
2) RJ Sweeney, VM Prozesky, KS Viljoen and SH ConnellThe sensitive determination of H in diamond by infrared (FTIR) spectroscopy and micro-elastic-recoil (m-ERDA) techniquesNucl. Instr. & Meth. in Phys. Res. 158 (1999), 582-587
3) E Sideras-Haddad, SH Connell, JPF Sellschop, R Hart and M TredouxAnomalous Fe and Mn heterogeneity observed in microscopic inclusions in diamond using nuclear microscopyNucl. Instr. & Meth. in Phys. Res. 158 (1999) 612-615
4) SJ Piketh, E Sideras-Haddad, K Holmgren, PD TysonProton micro-probe analysis of a stalagmite from South AfricaNucl. Instr. & Meth. in Phys. Res. 158 (1999) 606-611
5) RD Maclear, JE Butler, SH Connell, BP Doyle, IZ Machi, DB Rebuli, JPF Sellschop, E Sideras-HaddadThe distribution of hydrogen in polycrystalline CVD diamondDiamond and Related Materials 8 (1999) 1615-1619
6) DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF SellschopOxygen on Diamond SurfacesDiamond and Related Materials 8 (1999) 1620-1622
7) IZ Machi, JE Butler, SH Connell, BP Doyle, RD Maclear, JPF Sellschop, E Sideras-Haddad, and D RebuliDiffusion Characteristics of Hydrogen in DiamondDiamond and Related Materials 8 (1999) 1611-1614
8) CG Fischer, SH Connell, PG Coleman, W Anwand, G Brauer, F Malik, JPF SellschopA slow positron beam investigation of positron-defect interaction in single crystalline synthetic type IB diamonds and a natural type IIB diamondApplied Surface Science (1999)
9) IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear, BP Doyle, JE Butler, R Scheuermann and A Seeger.Muonium studies of p-type semi-conducting diamond under conditions of UV-visible illuminationHyp. Int. 120/121 (1999) 585-589
10) JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt, P Murphy, RWN Nilen, and JPF Sellschop
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Longitudinal Field - Muon Spin Relaxation (LF-mSR) measurements and evidence for a new muonium defect site in type Ia diamondHyp. Int. 120/121 (1999) 579-583
11) M.G. Bossenger, S.H. Connell, E. Sideras-Haddad, H. Appel, B.P. Doyle, W. Verwoerd, K. Bharuth-Ram, J.P.F. Sellschop, C.G. Fischer and V. NoltingSite occupancy and molecular complex formation of 19F ions in fullerenes C60 and C70 studied by TDPADHyp. Int. 120/121 (1999) 557-562
12) K Kirsebom, YuV Kononets, U Mikkelsen, SP Møller, KT Nielsen, E Uggerhøj, T Worm, K Elsener, C Biino, S Ballestrero, P Sona, SH Connell, JPF Sellschop, ZZ Vilakazi.Enhanced electromagnetic showers initiated by 20-180 GeV gamma-rays on aligned thick germanium crystals.Nucl Instr. & Meth. in Phys. Res. B (1999) 472-478
13) K Kirsebom, YuV Kononets, U Mikkelsen, SP Møller, E Uggerhøj, T Worm, K Elsener, C Biino, S Ballestrero, P Sona, RO Avakian, K Ispirian, SP Taroian, SH Connell, JPF Sellschop and ZZ Vilakazi.Generation and detection of the polarisation of multi-GeV photons by use of two diamond crystalsPhys. Lett B 135 (1998) 347-353
14) E Gadioli, M Cavinato, E Fabrici, E Gadioli Erba, C Birattari, I Mica, S Solia TG Stevens, SH Connell, JPF Sellschop, GF Steyn, SV Förtsch, JJ Lawrie, FM Nortier and AA Cowley.Alpha particle emission in the interaction of 400 Mev 12C with 59Co and 93NbProceedings of the The Nucleus: New Physics for the New Millennium Faure, South Africa, 18 - 22 January 1999 by Plenum Publishing Corporation
15) E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, V Allori, G Bello, F Cerutti, A di Filippo, TG Stevens, SH Connell, JPF Sellschop, FM Nortier, GF Steyn, C MarchettaThe Interaction of 12C and 16O with 103RhHeavy Ion Physics 7 (1998) 275 - 287
16) E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, V Allori, G Bello, F Cerutti, A DI Filippo, S Vailati, TG Stevens, SH Connell, JPF Sellschop, FM Nortier, GF Steyn, C MarchettaAngular Distributions and Forward Recoil Range Distributions of Residues Created in the Interaction of 12C and 16O with 103RhNucl Phys A 641 (1998) 271
17) E Gadioli, M Cavinato, E Fabrici, E Gadioli Erba, C Birattari, TG Stevens, SH Connell, JPF Sellschop, FM Nortier, GF SteynThermalization of the Intermediate Nuclei in Fusion and Incomplete Fusion ReactionsProceedings of the Predeal School on Structure and Stability of Nucleon and Nuclear Systems 1998 World Scientific
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18) SH Connell, JPF Sellschop, JE Butler, RD Maclear, BP Doyle, IZ MachiA study of the mobility and trapping of minor hydrogen concentrations in diamond in three dimensions using quantitative ERDA microscopyDiamond and Related Materials, 7 (1998) 1714 - 1718
19) RD Maclear, SH Connell, BP Doyle, IZ Machi, JE Butler, JPF Sellschop, SR Naidoo, E FritschQuantitative trace hydrogen distributions in natural and synthetic diamond using 3D-micro-erda microscopyNucl Instr and Meth in Phys. Res B 136-8 (1998) 579 - 582
20) K Kirsebom, U Kononets, U Mikkelsen, SP Moller, E Uggerhoj, T Worm, C Biino K Elsener, S Ballestrero, P Sona, SH Connell, JPF Sellschop, ZZ Vilakazi, A Apyan, RO Avakian, K Ispirian.Pair production by 5-150 GeV Photons in the strong crystalline fields of germanium, tungsten and iridiumNucl Instr. & Meth. in Phys. Res. B 135 (1998) 143-148
21) B.P. Doyle, J.K Dewhurst, J.E. Lowther and K. Bharuth-RamLattice locations of indium implanted in diamondPhys. Rev. B, 57 (1998) 4965-4967.
22) KL Bhatia, S Fabian, S Kalbitzer, Ch Klatt, W Kratschmer, R Stoll and JPF SellschopOptical effects in carbon-ion irradiated diamond.Thin Solid Films 324 (1998) 11-18
23) JPF SellschopProduction of diamond single crystals for synchrotron X-ray beamlinesProc of SPIE 3448 (1998) 40 - 52 in Crystal and Multilayer Optics Editors: Albert T Macrander, Andreas K Freund, Tetsuya Ishikawa, Dennis M Mills
24) AK Freund, JPF Sellschop, K Lieb, S Rony, C Schulze, L Schroeder, J TeyssierRecent diamond single crystal X-ray optics developments at the European Synchrotron Radiation FacilityProceedings of SPIE 3448 (1998) 53 - 63 in Crystal and Multilayer Optics Editors: Albert T Macrander, Andreas K Freund, Tetsuya Ishikawa, Dennis M Mills
25) JPF Sellschop, P KienleMethod of making carbon with electrically active sitesProvisional patent, #98/2242, filed on 17 March 1998
26) JPF SellschopA method of altering the colour of a materialProvisional patent, #98/5495, filed on 24 June 1998
27) JPF SellschopMethod of producing n-type doped carbonProvisional patent, #98/8792, filed on 25 September 1998
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28) JPF SellschopIsotope conversionProvisional patent, #98/10414, field on 13 November 1998
29) JPF Sellschoppn, junctionsProvisional patent, #98/10413, filed on 13 November 1998
30) M. A. G. Andreoli, L.D. Ashwal, R. J. Hart, and J. M. Huizenga.Petrology and Geochemistry of nickel, iridium-rich quartz norite from the late Jurassic Morokweng impact structure, South Africa.Special publications of the Geological Society of America 339 (1999) 1-18.
31) Marian Tredoux, Rodger J. Hart, Richard W. Carlson, Steven R. ShireyUltramafic rocks at the centre the Vredefort structure: further evidence for the crust-on-edge model.Geology 27 (1999) 923-926
32) R. J. Hart, D Moser, M. A. G. Andreoli.Archaen granulite facies rocks near the centre the Vredefort structure, South Africa: Implications for the evolution of the Kaapvaal craton.Geology 27 (1999) 1091-1094.
33) Marthinus Cloete, Rodger J Hart, Herbert K Schmid, Martyn Drury, Chris M. Demanet, K. Vijaya Sankar. Characterization of magnetite particles in shocked quartz by means of electron- and magnetic force microscopy : Vredefort, South AfricaContributions to Mineralogy and Petrology 137 (1999) 232-245
34) T Mauro, G Bench, E Sideras-Haddad, K Feingold, P Elias and C CullanderAcute Barrier Pertubation Abolishes the Ca and K Gradients in Murine Epidermis: Quantitative measurements Using PIXE. The Journal of Investigative Dermatology, Vol. 111, No 6 (1998) 1198-1201
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Conferences and Visits (1998)
International Conferences 1998
International Workshop on Radiation Physics with Relativistic Electrons, Tabarz, Germany 9 - 12 June 1998
JPF Sellschop (Invited)The production of thin and thick diamond targets for energetic electron and synchrotron radiation studies
1. ZZ Vilakazi, SH Connell, JPF Sellschop, U Mikkelsen, U Kononets, K Kirsebom, SP Moller, E Uggerhoj, T Worm, K Elsener, S Ballestrero, P Sona, C Biino, R Moore, RO Avakian, K Ispirian, A ApyanInvestigation of pair production and its dependence on correlated effects when multi-GeV photons are incident on Ge crystal
International Conference on Hyperfine Interactions, Durban August (1998)
1 Doyle, E.J. Storbeck, U. Wahl, S.H. Connell and J.P.F. SellschopStudy of indium-defect interactions in diamond using 2-D CEEC
2 Storbeck, U. Wahl, B.P. Doyle, S.H. Connell and J.P.F. SellschopA 2-D CEEC study of the second configuration observed for indium implanted into pure diamond
3 JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt, RWN Nilen, and JPF SellschopLongitudinal Field - Muon Spin Relaxation (LF-mSR) measurements in type Ia diamond
4 IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear, BP Doyl1, JE Butler, R Scheuermann, and A SeegerMuonium studies of p-type semi-conducting diamond under conditions of UV-visible illumination
5 SH Connell, IZ Machi, CG Smallman, JPF Sellschop, K Bharuth-Ram, RWN Nilen, J Major, R Scheuermann, and A Seeger Possible observation of quantum diffusion of MuT in diamond
6 M.G. Bossenger, S.H. Connell, E. Sideras-Haddad, H. Appel, B.P. Doyle, W. Verwoerd, K. Bharuth-Ram, J.P.F. Sellschop, C.G. Fischer and V. NoltingSite occupancy and molecular complex formation of 19F ions in fullerenes C60 and C70 studied by TDPAD
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International Symposium on Optical Science, Engineering, and Instrumentation : SPIE's 43rd Annual Meeting 1998
1 JPF SellschopProduction of diamond single crystals for synchrotron X-ray beamlines
2 AK Freund, JPF Sellschop, K Lieb, S Rony, C Schulze, L Schroeder, J TeyssierRecent diamond single crystal X-ray optics developments at the European Synchrotron Radiation Facility
International Conference on Nuclear Microprobe techniques and Applications, Stellenbosch, 11 - 16 October 1998
1 DB Rebuli, E Sideras-Haddad, BP Doyle, RD Maclear, TE Derry, SH Connell, P Aggerholm, JE Butler, JPF SellschopOxygen surface studies in ultra-thin diamonds using transmission channeled Rutherford Forward Scattering
2 SH Connell, BP Doyle, IZ Machi, RD Maclear, DB Rebuli, JPF Sellschop and E Sideras-HaddadHydrogen chemistry and dynamics in diamond studied using 3D-ERDA microscopy
3 E Sideras-Haddad, SH Connell, JPF Sellschop, R Hart and M TredouxAnomalous Fe and Mn heterogeneity observed in microscopic inclusions in diamond using nuclear microscopy
4 SJ Piketh, E Sideras-Haddad, K Holmgren, PD TysonProton micro-probe analysis of a stalagmite from South Africa
International Conference on New Diamond Science and technology, Pretoria, 31 August - 2nd September 1998
1 RD Maclear, JE Butler, SH Connell, BP Doyle, IZ Machi, DB Rebuli, JPF Sellschop, E Sideras-HaddadThe distribution of hydrogen in polycrystalline CVD diamond
2 DB Rebuli, TE Derry, E Sideras-Haddad, BP Doyle, RD Maclear, SH Connell, JPF SellschopOxygen On Diamond Surfaces
2 IZ Machi, JE Butler, SH Connell, BP Doyle, RD Maclear, JPF Sellschop, E. Sideras-Haddad, and D. RebuliDiffusion Characteristics of Hydrogen in Diamond
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Eighth International Workshop on Slow Positron Beam Techniques for Solids and Surface, SLOPOS - 8, Cape Town, 6 - 12 September 1998
1 CG Fischer, SH Connell, PG Coleman, W Anwand, G Brauer, F Malik, JPF SellschopA slow positron beam investigation of positron-defect interaction in single crystalline synthetic type IB diamonds and a natural type IIB diamond
2 CG Fischer, SH Connell, PG Coleman, F Malik, JPF SellschopA slow positron beam depth profiling of single crystalline natural type IIA, type IIB and synthetic type IB diamonds
Abstract in Proceedings of 17th general meeting of the International mineralogical association. Toronto, Canada, August 1998
1 Cloete M, Hart R, Schmid H, Demanet C, Sankar V, Mar? L and Drury M. Crystallographic and magnetic orientations of magnetite particles in shocked quartz, Vredefort, South Africa.
Symposium on Witwatersrand and Vredefort Metamorphism and Mineralization, Cape Town February 1998
1 Rodger Hart, Marco Andreoli, Desmond Moser and Marian Tredoux. Bushveld beneath the Vredefort structure: fact or fiction?
Impacts and the early Earth workshop, Cambridge, 1998
1 Iain McDonald , Rodger J. Hart , Marco A.G. Andreoli , and Marian Tredoux. Platinum-Group Element Geochemistry Of The Quartz Norite Impact Melt From The Morokweng Structure, Southern Africa: Clues To The Type Of Impactor.
The 62 nd Annual Meteoritical Society Meeting Johannesburg, 11th to 16th July 1999.
1 R.J. Hart and M. CloeteImpact related magnetic rocks from the vredefort impact structure
Diamond Conference, London, England, July 1998
1. B Doyle, R Maclear, JPF Sellschop, SH Connell, E Sideras-Haddad and JE ButlerWhere is the hydrogen in CVD diamond?
2. JM Baker, IZ Machi, SH Connell, K Bharuth-Ram , JE Butler, SFJ Cox, CG Fischer, T Jestadt, RWN Nilen and JPF SellschopLongitudinal field muon spin relaxation (LF-SR) measurements in type IA diamond
3. E Sideras-Haddad, D Rebuli, SH Connell, JPF Sellschop, B Doyle and R MaclearOxygen on diamond
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4. IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, R Maclear, BP Doyle, JE Butler, R Sheuerman and A SeegerStudy of diamond and its defects using transverse field muon spin rotation (TF-SR)
5. CG Fischer, SH Connell and JPF SellschopNear surface to bulk characterisation of diamond by positron annihilation
6. JPF Sellschop, A Freund, W Greiner and M RebakOn the bending of diamond
7. SH Connell, IZ Machi, CG Smallmann, JPF Sellschop, K Bharuth-Ram, RWN Nilen , J Major, R Scheuerman and A SeegerQuantum diffusion of the interstitial muonium (MuT) in diamonds with induced vacancies
8. E Storbeck, B Doyle, SH Connell, JPF Sellschop and U WahlLattice location studies of In-111 in diamond using the Isolde facility at CERN
9. JM Baker, P Murphy, IZ Machi, SH Connell, K Bharuth-Ram, SFJ Cox, JE Butler, CG Fischer, T Jestadt, RWN Nilen and JPF SellschopMuonium at a site of rhombic symmetry in type Ia diamond
Local Conferences
SAIP Conf, UCT, 8-10 July 1998
1. Maclear, S.H. Connell, M. Hogan, A.H. Andeweg, J.P.F. Sellschop and F. Weehuizen, The Schonland Research Centre EN-Tandem Accelerator Control System,South African Institute of Physics Conference, Cape Town, 8-10 July, 1998
2. Doyle, S.H. Connell, J.P.F. Sellschop and U. Wahl,PAC study of indium-defect interactions in diamond
3. Doyle, E.J. Storbeck, U. Wahl, S.H. Connell and J.P.F. Sellschop,Study of indium-defect interactions in diamond using 2-D CEEC
4. Storbeck, U. Wahl, B.P. Doyle, S.H. Connell and J.P.F. Sellschop.A 2-D CEEC study of the second configuration observed for indium implanted into pure diamond
5. Doyle, J.E. Butler, S.H. Connell, I.Z. Machi , R.D. Maclear, J.P.F. Sellschop and E. Sideras-Haddad,
Diffusion Characteristics of Hydrogen in CVD Diamond
6. Sideras-Haddad, S.H. Connell, J.P.F. Sellschop, R. Hart and M.Tredoux,Anomalous Fe and Mn zoning observed in microscopic inclusions in diamond using nuclear microscopy
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7. JM Baker, IZ Machi, SH Connell, K Bharuth-Ram, JE Butler, SFJ Cox, CG Fischer, T Jestadt, RWN Nilen, and JPF Sellschop,Longitudinal Field - Muon Spin Relaxation (LF-SR) measurements in type Ia diamond
8. IZ Machi, SH Connell, J Major, CG Smallman, JPF Sellschop, K Bharuth-Ram, RD Maclear, BP Doyle, JE Butler, R Scheuermann, and A Seeger,Muonium studies of p-type semi-conducting diamond under conditions of UV-visible illumination
9. R.D.Maclear, S.H. Connell, E. Sideras-Haddad, D.B. Rebuli, B.P. Doyle, I.Z. Machi, J.E. Butler, P. Aggerholm and J.P.F. Sellschop,Channeling studies of ultra-thin diamond films
10. E Gadioli, C Birattari, M Cavinato, E Fabrici, E Gadioli Erba, E Allori,V Ceruti, A Di Filippo, E Galbiati, TG Stevens, SH Connell, JPF Sellschop, Sj Mills, FM Nortier, GF Steyn, C MarchettaA comprehensive study of the interaction of 12C with 103Rh up to 33 MeV/nucleon
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Visits of Staff and students to International Institutions
Conferences Attended and Institutions visited 1998Date Institution Country PurposeMarch (1 week)ZZ VilakaziSH Connell
INFN - Florence Italy NA43 collaborators' meeting
May (1week)IZ Machi
PSI-Zurich Switzerland Expt Evaluation Committee Meeting
June (1 week)ZZ VilakaziJPF Sellschop
Tabarz Germany International Workshop -Rad. Phys. with rel. e-
June (1.5 months)CG Fischer
Uni-BristolUni-East AngliaRossendorf
England and Germany
Working visits on ACAR and SlowPos Spectroscopy
June/July (2 weeks)BP Doyle
ICTP Trieste Italy Electronic Structure Calculations Workshop and Hyperfine Interactions conference
July (1week)JPF Sellschop
San Diego USA SPIE's 43rd Annual Meeting 1998
July (1week)JPF Sellschop
London UK Diamond Conference
August (1week)SH Connell, E Sideras-Haddad + 2 students
Durban RSA Hyperfine Interactions Conference
August (1week)SH Connell, E Sideras-Haddad + 2 students
Pretoria RSA New Diamond Science and Technology Conference
September (1week)SH Connell, E Sideras-Haddad + 2 students
Stellenbosch RSA Nuclear Microprobe Conference
September (1week)1 student
Cape Town RSA Slow Positrons Conference
Feb/March and Sept/October(5 Weeks)SH Connell, JPF Sellschop, E Sideras-Haddad
National Accelerator Centre, Faure
RSA Working visits
July (1 week)SH Connell, E Sideras-Haddad5 students
UCT, Cape Town RSA SA Inst of Physics national conference
August (1 week) Toronto Canada 17th general meeting of
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RJ Hart the International mineralogical association
Sept (1 week)RJ Hart
Cambridge UK Impacts and the early Earth workshop
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Visiting Scientists to WITS
Sabbatical Visits1 Mr P Aggerholm
(Senior Technician : Institute for Physics and Astronomy, University of Aarhus, Denmark)One year sabbatical, starting January 1998.
2 Prof EJ Sendezera(Professor : Physics Department, University of Zululand)(One year sabbattical starting August 1997)
Working Visits1 Prof. E gadioli, Prof C C Birattari and student(s)
(INFN-Milano) Two working vists per year of three weeks each in February and SeptemberShort Vists
1 Dr Marc CaffeeCAMS (Centre for Accelerator Mass Spectrometry) at Lawrence Livermore National Lab, USA.Two days, January 1998
2 Dr. Soye SieDirector of the HIAF (Heavy Ion Analytical Facility) at CSIRO, Sydney- AustraliThree days, September 1998
3 Dr. Mark RobertsFacility manager of CAMS (Centre for Accelerator Mass Spectrometry) at Lawrence Livermore National Lab, USAThree days, September 1998
4 Prof HH AndersenPhys Dept, Aarhus University and Editor of Nucl instr & Methods B One day, October 1998
5 Dr RokitaPolish Institute of Nuclear SciencesOne day, October 1998
6 Prof B Asman Phys Dept Uppsala universityOne week, November 1998
Postgraduate Students
Students (graduated in 1998)Name Supervisor Thesis title, progress and awardsR Nilen(MSc,PhD-WITS)
SH Connell,JPF Sellschop
Jan 1994-Sept 1998
Positron Spectroscopy in DiamondCurrently a Post Doc at the SRCNS under JPF SellschopWon 3 best PhD oral presentation prizes at the SAIP, 3rd best student oral at ICPA in Kansas 1997
Z Vilakazi(PhD-WITS)Jul 1994 -
SH Connell,JPF Sellschop
Jul 1994 -Sept 1998
Radiation from Multi-Hundred GeV electrons and positrons incident on CrystalsCurrently a Post Doc at CERN and Lecturer at UCT
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Best PhD presetnation at SAIP-98 in Nuclear and Particle physics section
Students not yet graduated by 1999Name Supervisos Thesis Title Status, progress and awardsE StorbeckMSc,PhD -WITS)Jan 1991 -(PT)
SH Connell,JPF Sellschop
Study of wide-band gap semi-conductors, specifically diamond, through emission electron channeling.
Thesis submittedEmployed at SAMES for one year, One year at the Rochester Inst of Technology, now in Information Technology.
T Stevens(MSc, PhD - (WITS)Jan 1993 - (PT)
SH Connell,JPF Sellschop
Nuclear reaction mechanisms by stacked foil techniques
Completed expt work, analysis + interptretation. Well advanced with 1st draft of Thesis. Employed at the AEC MLIS program until its closure (one year). Now in the IT industry
B Doyle(MSc, PhD-WITS)1995 - (FT)
SH Connell,JPF Sellschop
Impurity reactions in diamond
Submitted. Now on a post-doc at the ESRF
I. Z. Machi(PhD - WITS)1995 - (FT)
SH Connell,K. Bharuth - Ram
Hydrogen and Muonium in diamond
Submitted. Now on the staff of UNISA Physics Dept
R.D. Maclear(MSc, PhD - WITS)(FT)
SH Connell,JPF Sellschop
Excellent progress, Experimental work almost complete. Writing.
C.G. Fischer(MSc, PhD - WITS)(FT)
SH Connell,DJ Britton
Excellent progress, Experimental work complete. Analysis + write-up in progress. Has studied Financial Maths concurrently with Physics.
AU Naran(MSc - WITS)Jun 99 -
E Sideras-HadadSH Connell
Ion Beam Interactions in Thin Diamond Films
Just begun
D B Rebuli(PhD - WITS)July 1999 -(FT)
E Sideras-HadadSH Connell
Accelerator Mass Specrometry
Just begun
B FlowersPhD
RJ Hart Impact structures
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HEALTH PHYSICS SERVICE
1st January 1998 to 31st December 1998
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Introduction
The Health Physics Service was established by the University to ensure that all materials and machines that produce radiation, are used and disposed of safely by both staff members and students of the University. This is to safeguard both personnel and environment from the harmful effects the uncontrolled use of radiation, may give rise to.
In this country various acts were enacted to control the use of radioactive material. In particular, the Hazardous Substances Act sets out the regulations that deals with the acquiring, use, transport and eventual disposal of radioactive materials and electronic products which produce radiation, be it ionising or non-ionising radiation. The vested control lies with the Department of Health. The Council for Nuclear Safety on the other hand, is the regulatory commission for the use of nuclear material. The regulations for the use of such material are covered by the Nuclear energy Act.
Thus in addition to the statutory obligation, the Service has a general duty of care. This mandate extends beyond the Main Campus to encompass the Medical School as well as part of the Chris Hani Baragwanath Hospital.
On the University campuses the prominent sources of ionising radiation can be grouped into two. The one group consists of machines that produce radiation and the other group consists of radioactive material that emits radiation. The latter may in turn be divided into what are known as sealed or unsealed sources of radiation.
Of the number of machines that produce ionising radiation, the University currently has in its possession five accelerators, thirty-one X-ray machines, and seven electron microscopes on its Campuses.
It has two hundred and eighty sealed sources, of that, two, because of its strength (radioactivity), are housed in, what is generally referred to as, irradiation facilities that require major biological shielding and safety interlocks. One of these is located at the Medical School and the other at the Schonland Research Centre.
In addition to the above mentioned sources of radiation, the University has a number of researchers who make use of the nuclear reactor facility that is situated at the Pelindaba site, for their neutron activation studies. This usage often results in a wide range of neutron-activated radioisotopes being produced in samples that are then brought onto the University campus for analysis.
Such varied activities currently engaged in by both our staff and student researchers, may subject them to distinct risks of exposures to such different types of radiation as alpha, beta, gamma and neutron radiation. This is especially true if adequate work procedures and precautions are not insisted upon.
The Service has therefore the following set-ups as its function:
- ensuring that the workplace and work procedures are designed to keep exposure to radiation as low as possible;
- obtaining all necessary approvals, authorisations and licences;
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- ensuring that doses estimated to have been received by staff and students comply with the relevant dose limits;
- ensuring that the doses estimated to have been received by members of the public from the operation comply with the public dose limits;
- developing a plan for dealing with incidents and accidents involving exposure to radiation;
- providing consultation for staff and students who may be exposed to radiation in the course of their work;
- keeping records of radiation exposure resulting from the operation;
- providing copies of dose records to staff and students on request;
- developing and implementing a plan for monitoring exposure to radiation and for estimating doses received by those exposed;
- controlling the purchase and use of radiation producing materials and machines by staff and students; and
- ensuring that all radiation producing materials and machines are disposed of safely and in accordance with local and international standards and recommendations.
In addition to the controlling functions mentioned above, the Service provides a personnel-monitoring service, a decontamination service and a waste disposal service on a routine basis to the University community. The Service runs an in-house service for the checking of radiation monitors used by the various departments and as well offers on short term loan, health physics instrumentation to both staff and post-graduate students involved with radiation work. Its advice to users of the Service on instrumentation, materials and experimental procedures covers both technical and scientific aspects.
Also, of the two cobalt irradiation facilities it oversees, the Service maintains and runs the Schonland-based facility.
Besides the “routine” aspects mentioned above, the Service undertakes a limited amount of research and teaching. It is felt that such activities are necessary in order to maintain a service that is professional to both staff and students of the University.
The teaching covers aspects of health physics and the research covers areas of radiation and health physics.
Staff
The Service has the following staff complement:
Dr T.L. Nam Director Radiation Protection Officer / ResponsiblePerson (In terms of the Statues)
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Prof. R.J. Keddy Honorary ConsultantActing Radiation Protection Officer / AlternateResponsible Person (In terms of the Statues)
Mr. J. Geyer Senior Technician
Mr. Geyer is currently the senior technician at the Service. He replaces Mr. Ramerafe who resigned after being with the Service for just over two years.
Staff Training
To facilitate effective integration into the Service, Mr. Geyer has been allotted such tasks as the setting up and testing of the recently acquired health-physics instrumentation. These are instruments donated by the International Atomic Energy Agency (IAEA) to the University for the training of post-graduate students in radiation protection.
Radioactive Waste
The Health Physics Service continues to provide user departments with a waste disposal service. To reduce costs, the Service currently makes use of departmental assistance for the loading of containers onto transport-vehicle whenever possible. For the bulk collection of waste that are stored at Schonland Research Centre and are awaiting bulk delivery to the Pelindaba disposal site of the Atomic Energy Corporation(AEC), the Service has for the past year and a half, commissioned the Service of the AEC for the task.
This policy has shown to be not only flexible and but cost effective. It has also alleviated the past problem concerning the availability of manpower to assist in the loading and off loading of waste drums. Furthermore, it has the added advantage of reducing the risk of accidents/incidents involving the transport of radioactive material over longer distances.
As was reported previously, the Service continues to make use only of vehicles fitted with a tracker system for the transport of radioactive material.
General
As in the previous year, it can again, be reported that no incident of friction involving staff members or students and the Service has occurred over the past year. The Service has on the whole received full co-operation from the University community in the pursuit of its functions.
Nuclear Non-proliferation Inspection
Two members of the International Atomic Energy Agency’s (IAEA) safeguards team together with a member from the Atomic Energy Corporation conducted an inventory of depleted uranium on the University campus. This forms part of their annual inventory-verification of nuclear material in the country. I am pleased to report that in their submission, the inspectors expressed satisfaction over the University’s control and use of such materials.
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Teaching
As in previous years the Service continued to partake in formal courses offered by the Department of Medical Physics and Department of Physics at Honours level on aspects of Radiation Protection to students that chose Medical Physics as a topic.
Research
The research component of the Service centred on aspects of radiation physics. It is a collaborative effort carried out jointly with members of the Department of Medical Physics and the Health Physics Service. In the past year, the research effort of the group was directed mainly at the identification of the parameters and the physical processes that are important for solid materials to perform effectively as detectors of various types of radiation.
Non-University users of the Service
As in previous years the Service had during the course of the year received numerous queries from school pupils and members of the general public on matters pertaining to radiation and the hazards arising from its use. Where possible reference material were provided on request.
It can be reported that during the same period, a number of outside organisations also made use of the Health Physics Service.
The Post-graduate Course Radiation Protection
More than three years ago the International Atomic Energy Agency (IAEA), and the South African Council for Nuclear Safety approached the University through the Schonland Research Centre with the view to establishing a post- graduate course in radiation protection. The main objective of the IAEA is to establish regional training centres for the post graduate course at leading educational institutions of selected member countries.
It was proposed that this University would serve as a training centre for the entire African region, that the courses would be integrated into the curricula of the University and that the first training course would begin in 1999.
The Agency would in turn undertake to assist by
(1) providing grants for capital equipment needed for training. This amounts to well over a million rand over a two year period.
(2) providing consultants and lecturers to assist with establishing and conducting the course.
(3) providing grants and bursaries for foreign students.
Following this, the Schonland Centre and the Physics Department approached the Service to assist in the development of this initiative.
In view of the following possible implications such a course will have:
(1) for the University in terms of income, if ran properly;
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(2) for the Service in terms of equipment available;
(3) for the University in terms of possible increase in the number of masters and post-masters students;
(4) for members of the Service in terms of professional contacts with both local and international practitioners in the field of radiation protection;
(5) for the Service to both enhance and contribute the professional and academic expertise it has accumulated over many years, it was felt that the Service should and would respond within its manpower constraints, positively to the invitation.
The Service has to date provided the following input:
(1) As the proposed course is envisaged to form part of the new initiative by the Faculty of Science to offer a Post-Graduate Diploma in the Sciences or as part of an MSc by course work and research report from 1998 onwards, the Service made various suggestions for changes to the rules involving the admission requirements to the course as well those which concern the awarding of the diploma and degree, when they were being drawn up. It can be reported that many of the recommendations, which took into account that most of the students targeted are young professionals, now form part of the rules for the post-graduate diploma.
(2) The Service was directly and proactively involved in choice of capital equipment that will be used not only for postgraduate training in radiation protection, but will be made available for research and for routine monitoring by members of the Health Physics Service and other researchers of the University.
(2) Based on the guidelines provided by the IAEA and within the constraints of the Faculty of Sciences’ point system, the Service, with the assistance from a member for the Council for Nuclear Safety that was seconded to the University, drafted a proposed structures for the syllabus for the Post-graduate Diploma in Radiation Protection.
(3) (4) Over the past year, the Service has contributed significantly to the design and supervision of building alterations and as well as in the design and the choice of furniture and fixtures that is needed for the training centre.
One should perhaps also mention that both the nuclear industry and legislative bodies in the country are of the opinion that organisations should use adequately trained and experienced radiation protection specialists in radiation controlling functions. Plans are afoot to have such personnel accredited by an accreditation board in the foreseeable future. This of course implies that there may be opportunities for the University to offer appropriate training courses to potential users of radioactive material and hence extend the use of the newly established training centre at the Schonland.
Visitation
Not only did the Service played host to participants of the radio-isotope course offered by the Witwatersrand Technikon on their annual visitation to the Schonland Research Centre during the year, it also provided the Technikon with portable radiation monitoring equipment and radio-active sources on loan, for the duration of the course.
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As a preliminary exercise to the holding of a postgraduate course in radiation protection, workshops for post-graduate students from Africa were arranged by the IAEA and held
at the University during the year. Members of the Service, when time permitted, participated actively in the hosting of the students from the eight African countries, at the Schonland Centre.
Non-ionising Radiation
As in the previous year, a number of enquiries were received from concerned staff members and post-graduate students, of radiation levels around standard microwave ovens and microwave ovens that were modified for research purposes.
Equipment
As in the past, a number of our staff and students made use of some of the equipment the Service has at its disposal. The Service has a range of equipment that it makes available to the University community on a short term loan basis.
Medical School-based Teletherapy Unit
Up until 1995 the Department of Surgery was the most frequent user of this facility. The number of irradiations undertaken by the Department for 1995 was 584. The figures for the subsequent two years namely, 1996 and 1997 were 7 and 6 respectively. For the same period ending in December 1998, usage again increased. The figure for the year, was 184. The Central Animal Services, on the other hand had steadily increased its usage over the same period. Its number of irradiations increased from 165 in 1995, to 265 in 1996 and 321 in 1997. For 1998 this stabilised to just over the 300 mark at 309.
The total number of irradiations increased from 333 in 1997 to 628 for the same period last year. The minor users of the facility in 1998 were the Departments of Medical Biochemistry and the South African Blood Transfusion Services.
It should again be pointed out that the facility is at least thirty years old. Time and money need therefore, to be allocated for routine maintenance. The Service shares the concern expressed by the Central Animal Service and the Department of Surgery regarding the cost of maintaining the facility. It is clear that an amount has to be set aside for both routine maintenance, and source replacement.
An area often not considered by users of relatively active radioactive sources is question of eventual disposal of such source.
It should perhaps be stressed that a policy regarding the disposal of large radio-active sources that have relatively long half-lives and that are no longer needed, needs to be in place to take into account the non-trivial cost of such eventuality.
Schonland-based Irradiation Facility
The only users of the facility over the past year were researchers from the Schonland Research Centre and the National Institute of Virology.
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This under utilisation can be attributed to the activity of the present source which currently less than one tenth of its original activity.
Acknowledgements
The Service acknowledges with appreciation Prof. R.J. Keddy’s continued involvement and contribution to the Health Physics Service; both in his capacity as Chairman of the Users’ meeting and as Honorary Consultant to the Service.
We wish also to record our sincere thanks to the Buying Office and all the departmental radiation-supervisors, for their assistance and contributions. It can be said that their input contributed much to the smooth running of the Service.
TL Nam
October 1999
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