fair: at the frontier of nuclear structure physics
DESCRIPTION
FAIR: At the Frontier of Nuclear structure Physics. W.Gelletly. Physics Department,University of Surrey. Obergurgl -02/10/2007. Lecture 2. The Story so far--------. We looked at a) our present theoretical understanding of Nuclear Structure. b) Some simple physics from the undergraduate - PowerPoint PPT PresentationTRANSCRIPT
Obergurgl -02/10/2007 Lecture 2
The Story so far--------
We looked at a) our present theoretical understanding of Nuclear Structure
b) Some simple physics from the undergraduate curriculum – which turned out not to be so straightforward.
c) Ways to study nuclear structure.
We saw that we needed beams of Radioactive nuclei!!
Now we want to look at how we can produce beams of radioactive ions.
We will find that this leads us inexorably to FAIR
Manipulating the system
Beam energyBeam energy spreadBeam speciesTarget speciesForm of target
We control
We can examine how properties vary with
Energy (temperature)Angular momentum (spin)Isospin or (N-Z)/A
Radioactive ion beams, production techniques
Isotopic separation on-line (ISOL)
thick target (100% of range) => high beam current (upto1016 s-1) long extraction and ionization time (ms) chemistry dependent
light projectilethick target
difussion
ion source
post-acceleration
mas separatorlow- or high-energy nucleus
short separation+identification time (100 ns) thinner targets (10% of range) =>lower beam currents (upto 1012 s-1) chemistry independent
high-energy nucleus
In-flight fragmentation
heavy projectilethin target spectrometer
J. Benlliure
Production techniques
J. Benlliure
Isotopic separation on-line (ISOL)
light projectile into a heavy target nucleus (target spallation) charged and neutral projectiles (n) thick target (100% of range) and high beam current (1016 p/s) high quality beams
long extraction and ionization time (ms) chemistry dependent target heat load activation
light projectile
thick target
diffusion
ion source
post-acceleration
mass separatorhigh-energy nucleus
Radioactive species are created in nuclear reactionsin a target-ion source maintained at high T.They diffuse/effuse from the target into an ion source where are ionised and then extracted by an electric field of ~ 60 keV.Following mass separation they can be used at 60 keVor injected into a post-accelerator to take them to the Coulomb Barrier or beyond.
EURISOL – The future ISOL facility for Europe
Eurisol is a very ambitious project. It is a classical ISOL facility with a driver accelerator delivering 5 mA of 1 GeV protons or intense deuteron beams etc. [cf present ISOLDE has 1.4 μA of 1.4 GeV protons]
This is beyond our current capabilities.
Accordingly several machines are being built as stepping stones to reach this future goal and there is intense development activity underway.
SPIRAL 2 at GANIL in France and HIE-ISOLDE at CERN are two such stepping stones.
So EURISOL represents a big challenge but it is a major goal for European
Nuclear Physicists.
Ionsources
1 GeV/qH-, H+, 3He++>200 MeV/q
D+, A/q=2
Chargebreeder
Low-resolutionmass-selector
UCx
target
1+ ionsource
n-generator
20-150 MeV/u (for 132Sn)
To low-energy areas
Secondaryfragmentation
target
One of severaltarget stations
High-resolution mass-selector
To medium-energy experimental areas
H-
H+, D+,3He++
9- 60 MeV/u 2-10 MeV/u
To high-energyexperimental areas
Chargeselector
SPL
HIE-ISOLDEEURISOL precursor
Production techniques
J. Benlliure
Gamma/neutron converters
low-energy nucleus
e-, d
thick target
diffusion
ion source
post-acceleration
mass separatorhigh-energy nucleus
converter
, n
This is the basis of SPIRAL II - one of the precursors of EURISOL, based on deuteron breakup
The emphasis here is on the production of neutron-rich species in the fission of Uranium induced by photons or neutrons.
The advantage of this technique is that it separates power dissipation and isotope production.
RFQ - 0.75A MeV
ECRIS-HI 1mA
“SILHI-deuteron” 5mA
CIME Cyclotron RNB (fission-fragments)
E < 6-7 MeV/u
SC - LINACE = 14.5 AMeV
HI A/Q=3E = 40 MeV - 2H
Int. = 5mA
Production Cave
C converter+UCx target
Low energy RNB
> 1013 fiss./s
•What is SPIRAL2 ?
Note:- LINAG will be a major new accelerator in its own right because of high intensity. System will also produce intense fluxes of fast neutrons. [Parallel operation]
LINAG
2. Fusion reaction with n-rich beams
1. Fission products (with converter)
4. N=Z Isol+In-flight5. Transfermiums In-flight
3. Fission products (without converter)
Primary beams: deuterons heavy ions
Regions of the Chart of Nuclei Accesible with SPIRAL 2 beams
Regions of the Chart of Nuclei Accesible with SPIRAL 2 beams
7. High Intensity Light RIB
6. SHE
8. Deep Inelastic Reactions with RNB
•Available Beams
Originally constructed by several CERN member states ~ 15 MCHF
Utilises now 50% ISOLDE running time
REX has accelerated 43 different RIB
Present RIB yield from ISOLDE allows 10% of all 700 radioisotopes be used
REX post-accelerator
Rex photo
REX-ISOLDE2006
MINIBALL(Coulex,transfer)
Halo studiese.g. 10LiJeppesen et alPL B642(2006)449
Coulomb barrier for RIB
Current REX-ISOLDE
HIE-ISOLDE
Radioactive ISOL beam yields
2020
2016
2012
present
GANIL-ISOLDEJan 07 agreement – Complementarity;Collaboration
Projectile Fragmentation Reactions
hotspot
Excited pre-fragment
Finalfragment
projectile
target
Energy (velocity) of beam > Fermi velocity inside nucleus ~30 MeV/uCan ‘shear off’ different combinations of protons and neutrons.Large variety of exotic nuclear species created, all at forward angleswith ~beam velocity. Some of these final fragments can get trapped in isomeric states.
Problem 1: Isotopic identification. Problem 2: Isomeric identification.
Main difficulty:- beam is a cocktail of many species
S t o p p i n g P o w e r o f R e l a t i v i s t i c H e a v y I o n s
B r e a k - d o w n o f t h e r e l a t i v i s t i c B e t h e t h e o r y ,F R S e x p e r i m e n t a l r e s u l t s w e r e t h e m o t i v a t i o no f t h e n e w t h e o r e t i c a l d e v e l o p m e n t b y J . L i n d h a r da n d A . H . S o e r e n s e n
Production of Exotic Nuclei at relativistic Energies
Production techniques
J. Benlliure
In-flight fragmentation
heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry
thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species
heavy projectile
thin target spectrometerhigh-energy nucleus
Identified by A and Z
In-flight Fragmentation (and Fission)
Ge
Relativistic energy fragmentation: => heavy ions (GSI unique!)
Fragment Recoil Separator
Such Separators exist at MSU, GANIL, RIKEN and GSI
Answer to our identification difficulty : - FRS
We will look at how it works later.
FAIR - Facility for Antiproton and Ion Research
100 m
UNILAC SIS 18
SIS 100/300
HESR SuperFRS
NESR
CRRESR
GSI todayGSI today FAIRFAIR
ESR
FLAIR
Rare-IsotopeProduction Target
AntiprotonProduction Target
Nustar three branches
“Facility for Antiproton and Ion Research (FAIR)” :
SIS 100/300
100 m
FAIRFAIRGSI todayGSI today
SIS 18UNILAC
ESR HESR SuperFRS
SuperFRS
RESR CR
NESR
Rare Isotope Prod.target
For example:DESPEC will have access to some key N=82 and N=126 r-process nuclei
Production techniques
J. Benlliure
Gamma/neutron converters(A variant of ISOL scheme)
Two-step reaction scheme(ISOL + Fragmentation)
e-, d
thick target
diffusion
ion source
post-acceleration
mass separatorhigh-energy nucleus
converter
, n
light projectile
fission
diffusion
ion source
post-acceleration
mass separator fragmentation spectrometer
Production techniques
J. Benlliure
In-flight fragmentation
heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry
thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species
low-energy nucleus high-energy nucleus
heavy projectile
thin target gas cell spectrometer
Current Schemes for producingbeams of radioactive nuclei
A)The classic ISOLDE scheme
B)The ISOL plus post-accelerator SPIRAL/REX-ISOLDE/LLN/ ISAC/HRIBF
C)Fragmentation -In Flight (GSI,MSU,GANIL,RIKEN)
D)The Hybrid-An IGISOL to replace the ISOL in B) -The basis of RIA
ISOL and In-Flight facilities-Partners
In-Flight ISOL
• Relativistic beams
• Universal in Z
• Down to very short T1/2
• Easily injected into storage rings
• Leads readily to colliding beam experiments
• High intensity beams with ion optics comparable to stable beams
• Easy to manipulate beam energies from keV to 10s of MeV
• High quality beams ideally suited to produce pencil-like beams and point sources for materials and other applied studies
It is probably true to say that if we worked at it virtually all experimentscould be done with both types of facility but they are complementary.
A.Richter, TH Darmstadt
What is the structure of nucleonic matter?
• Can we find a consistent theoretical framework that spans from few-body to many-body systems of nucleons?
• What are the Limits of nuclear existence?• What happens to the “Shell Structure” in highly dilute, neutron matter.• What new forms of nuclear matter will emerge in very loosely bound systems• Do the symmetries seen in near-stable nuclei
appear far from stability?• …..????
Goal: to determine nuclear properties over a wide range of N,Z,I,T, and find a consistent theoretical framework to describe the phenomena observed.
There are many unanswered questions:
Structure of the nucleon and other hadronsThe femtoscale frontier
Goal:- To understand the structure and properties of protons and neutrons and ultimately nuclei, in terms of the quarks and gluons of QCD
There are many unanswered questions:-
● What is the non-perturbative nature of QCD?
● What is the origin of the mass of the nucleon?
● What is the origin of the spin of the nucleon?
●Why do only two colourless configurations of quarks prevail?
●Do glueballs or quark-gluon hybrids exist?
●…………..?????
The role of nuclei in the Universe
Goal: to combine our knowledge of nuclear structure and theory with astronomical observations to model
astrophysical processes.
•The nuclear astrophysical origins of the chemical elements
• Can we identify the site(s) where the heavy elements are made?
•The manipulation of nuclear decay rates by controlling the nuclear medium
•Can we understand the mechanisms by which supernovae explode?
•Can we understand the dynamics of explosive stellar processes.
•Nuclear processes in the Early Universe
•……????
Many unanswered questions or badly understood processes:
Production techniques
J. Benlliure
In-flight fragmentation
heavy projectile into a light target nucleus (projectile fragmentation) short separation+identification time (100 ns) limited power deposition Independent of Chemistry
thinner targets (10% of range) and lower beam currents (1012 ions/s) beam is a cocktail of different nuclear species
high-energy nucleus
heavy projectile
thin target spectrometer
Ge
Detection setup
First half of spectrometer :-Momentum-to-charge selection plus beam rejectionSecond half we measure B, time-of-flight(T) and E in final detector.
Now we know B = mv/q, T = d/v, E = (q/v)2 -three unknowns (m,v and q)
From these measurements we identify A, Z and q for individual ions
In flight fragmentation (and fission) - Fragment Recoil Separator (GSI)
S. Pietri et al.,RISING data 107Ag beam
Cd
Ga
The Present Rare Isotope Facility at GSI
S IS F R S E S R
ALADIN
LAND
INJECTION FROM UNILAC
PROD UCTION TARG ET
12
3 FRS Branches
Low primary beam intensity (e.g. 108 238U /s) Low transmission for projectile fission fragments (4-10% at the FRS) Low transmission for fragments into the storage ring and to the
experimental areas Limited maximum magnetic rigidity (@ FRS: for U-like fragments, @ ESR:cooler performance and magnets, @ALADIN, to deflect
break-up fragments) Limited space in front of the production target Limited space at the experimental area 1 Limited space at the ESR injection area 2 Beam-line magnets, area 3, are not designed for fragment beams
Limitations
FR S
S uper-FR S D egrader
D egrader 1
D egrader 2
FRS (RISING) to Super-FRS(DESPEC)
H. Geissel et al. NIM B 204 (2003) 71
The Future of this kind of measurement
Note:-Super here means superconducting not------
Synchrotron
Synchrotron
Evacuated ring.
Dipole magnets with magnetic radius of curvature bend the particles round the ring.
Quadrupoles maintain focussing
Particles are accelerated in a number of RF cavities with circular frequency ω
Path = straight sections( in RF cavities, quadrupoles & some other sections) plus circular sections in dipoles. Hence R >
Synchrotron
No RF power -Initial E(i) and p(i)
T = 2R = 2RE(i) v p(i)c2
Corresponding circular frequency
Ω = 2 = p(i)c2 ---------- (A) T RE(i)
In addition magnetic field required is given by B = p(i)c q
RF turned on:- now ω = nΩ, where n is an integer. From (A) we see that the applied RF must increase with increasing energy up to the point where pc = E
Magnetic field must also increase:- ω = nΩ = nc pc nc; B =pc R E R q
SIS 18 at GSI
Synchrotron
Advantages:-
a) possible to accelerate electrons, protons, heavy ions etc b) Highest energies possible.
c) Basis of synchrotron radiation sources using electrons
Disadvantages:- a) Pulsed beam-takes 1 sec to accelerate particles in a large machine b) requires injection at high energy otherwise range of RF is too large In other words we need another accelerator to prepare the beam. At FAIR this will be the UNILAC.
The Super-FRS and its Branches
NuSTAR- [Nuclear Structure Astrophysics and Reactions] Collaboration
R3B
EXLELISE
ILIMA
Beam from SIS100/300