smurf research at texas a&m dr. tye w. botting texas a&m university
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SMURF Research at Texas A&MSMURF Research at Texas A&M
Dr. Tye W. Botting
Texas A&M University
Special
Microbeam
Utilization
Research
Facility
OverviewOverview
IntroductionBrief BackgroundCurrent ResearchFuture InterestsClosing Comments
BackgroundBackground
Synthetic Organic Chemistry• natural product precursor development
Environmental Testing• analytical equipment troubleshooting
Nuclear Chemistry• fission dynamics
Fission DynamicsFission Dynamics
Neutron calorimetry• The TAMU Neutron Ball
Timescale of nuclear fission• compare two conflicting methods• 4 reactions analyzed in detail• statistical model analysis of data
FOR MORE INFO...
TAMU Cyclotron Institute (http://cyclotron.tamu.edu)
Rate of Nuclear FissionRate of Nuclear Fission
Two “clocks” that did not seem to agree• Neutron evaporation clock• Giant Dipole Resonance (GDR) -ray clock
Required 150+ detectors• ~500 parameters per event• Required statistics produced 80+ GB of data
Statistical model calculations• Monte Carlo methods• Comparison with experiment yielded timescales
So, how fast So, how fast isis nuclear fission? nuclear fission?
Very fast!
~110-20 seconds
for medium-energy reactions
Current ResearchCurrent Research
Accelerator Development• Improvements and additions
Physics / Engineering• Krypton gas neutron detector• Hot water energy reclamation
Health Physics• Microdosimetry
Accelerator DevelopmentAccelerator Development
Ion source stabilityBeam developmentSoftware development
• Accelerator control• Microbeam targeting
Additions
Physics / EngineeringPhysics / Engineering
Improve understanding of the interaction of neutrons with matter
Develop new detector technologies Energy conservation / reclamation
Health PhysicsHealth Physics
Our main objective is to achieve a better understanding of risk to human health from everyday exposure to low doses of ionizing radiation.
Health Physics…Health Physics…
Evalaution of risk at low radiation doses has been based on linear extrapolation of observed effects of very high doses.
There are problems with this approach…
Health PhysicsHealth Physics
High-dose radiation exposure results in individual cells receiving multiple hits
Low-dose radiation exposure consists of sparsely distributed single hits
No reason to expect that a low-dose linear extrapolation model should work
Our ApproachOur Approach
Investigate both high- and low- linear energy transfer (LET) radiations
• positive ions (high LET)• electrons and X Rays (low LET)
Irradiate specific cells in vitro• use low doses directly• a line of cells on a dish, on individual cells• look for microscopic effects
– mutations
– cell-cell communication
ToolsTools
• Positive ion accelerator• 2MV Tandem Van de Graaff
• Electron accelerator• 100keV electrostatic accelerator
• X-ray apparatus• 1 Gray/min at Emax=250keV
• Hot water reflux apparatus• trial run in progress
2MV Tandem Van de Graaff2MV Tandem Van de Graaff
Alphatross Ion SourceBending and Focusing ElementsCharging System
• Tandem = “double ended”• Produces 4 MeV protons, 6 MeV alphas
Experimental Beam Lines• Neutron “beam”• Positive-Ion Microbeam
Ion Source
Accelerator Tank
Magnet
Accelerator Tank Magnet
Pelletron Charging SystemPelletron Charging System
Illustration courtesy of...
National Electrostatics Corp. (http://www.pelletron.com)
Experimental BeamlinesExperimental Beamlines
Neutron “beam”• Protons incident on LiF target
Positive-Ion Microbeam• 5m beam thickness• Targeting
– Individual cell nuclei– Line traces
Microscope Assembly direct and camera
Detectors (3 photomultipliers) special petri dishes go below
Fine collimators 2 sets of x and y axes
Beam Stop
Coarse collimators 1 set, only y axis
Microbeam
Cell culture dishesCell culture dishes
Electron AcceleratorElectron Accelerator
Only 4 feet high
Different type of collimator assembly
Accelerator tube has up to 100,000 Volts to produce up to 100keV electrons
ResultsResults
Accelerator Development• Improved ion-source stability• Added positive-ion microbeam assembly
– Made its endstation software functional
• Developed usable proton and neutron beams• Added neutron production beam line and facility• Always a work in progress!
Results…Results…
Physics / Engineering• Krypton gas neutron detector experiments run
– Data still being analyzed to determine next step(s)
• Hot water energy conservation / reclamation– Designed apparatus
– Construction nearing completion
– Should begin trial runs within the month
Results…Results…
Health Physics• X-ray irradiations (adapt and challenge)
– Appears low doses good for cell survival upon later higher-dose exposure
• Positive-ion irradiations– Mixed low-dose results (cell-line effect?)
• Electron irradiations– Appears that low fluence low-LET radiation is not
as damaging as predicted by the linear extrapolation model
Results NotesResults Notes
An interesting observation has arisen that irradiation of petri dishes prior to cell culturing seems to contribute to in vitro cell death.
Future DirectionsFuture Directions
At TAMU:• Continued accelerator development• Continued microbeam work
– Perhaps non-biological applications
• Further refinement of the Kr n-detectors• Hot water energy reclamation trial runs• Acquiring PIXE/RBS capability
Wider Future Directions…Wider Future Directions…
• Using PIXE/RBS to characterize surface pollution and degradation• Further investigation of irradiation pre-
treatment as a bio-inhibitory• Application of nuclear science methods in
materials science in general
Thank you all very much for your time and for the opportunity to visit both NCPTT and NSULA.
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