FAIR: At the Frontier of Nuclear structure Physics

1. FAIR: At the Frontier of Nuclear structure Physics W.Gelletly Physics Department,University of Surrey Obergurgl -02/10/2007 Lecture 2

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 FAIR

3. Manipulating the system We control • Beam energy • Beam energy spread • Beam species • Target species • Form of target We can examine how properties vary with Energy (temperature) Angular momentum (spin) Isospin or (N-Z)/A

4. Radioactive ion beams, production techniques low- or high-energy nucleus Isotopic separation on-line (ISOL) thick target ion source mas separator light projectile post-acceleration difussion  thick target (100% of range) => high beam current (upto1016 s-1)  long extraction and ionization time (ms)  chemistry dependent In-flight fragmentation thin target spectrometer heavy projectile high-energy nucleus  short separation+identification time (100 ns) • thinner targets (10% of range) =>lower beam currents (upto 1012 s-1) chemistry independent J. Benlliure

5. J. Benlliure high-energy nucleus Production techniques • Isotopic separation on-line (ISOL) thick target ion source mass separator light projectile post-acceleration diffusion • light projectile into a heavy target nucleus (target spallation) • charged and neutral projectiles (n,g) • 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

6. Radioactive species are created in nuclear reactions in 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.

7. 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.

8. n-generator UCx target H- One of several target stations 1+ ion source 1 GeV/q H-, H+, 3He++ H+, D+, 3He++ >200 MeV/q D+, A/q=2 SPL Ion sources Low-resolution mass-selector EURISOL precursor HIE-ISOLDE Secondary fragmentation target Charge selector High-resolution mass-selector Charge breeder 20-150 MeV/u (for 132Sn) 9- 60 MeV/u 2-10 MeV/u To high-energy experimental areas To low-energy areas To medium-energy experimental areas

9. low-energy nucleus high-energy nucleus Production techniques • Gamma/neutron converters ion source converter thick target mass separator g, n e-, d post-acceleration diffusion • 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. J. Benlliure

10. Low energy RNB > 1013 fiss./s • What is SPIRAL2 ? Production Cave C converter+UCx target CIME Cyclotron RNB (fission-fragments) E < 6-7 MeV/u LINAG SC - LINAC E = 14.5 AMeV HI A/Q=3 E = 40 MeV - 2H Int. = 5mA “SILHI-deuteron” 5mA ECRIS-HI 1mA RFQ - 0.75A MeV 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]

11. Regions of the Chart of Nuclei Accesible with SPIRAL 2 beams • Available Beams Primary beams:  deuterons  heavy ions 6. SHE 4. N=Z Isol+In-flight 5. Transfermiums In-flight 2. Fusion reaction with n-rich beams 1. Fission products (with converter) 3. Fission products (without converter) 8. Deep Inelastic Reactions with RNB 7. High Intensity Light RIB

12. REX post-accelerator • 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

13. Rex photo REX-ISOLDE 2006 MINIBALL (Coulex, transfer) Halo studies e.g. 10Li Jeppesen et al PL B642(2006)449

14. Coulomb barrier for RIB HIE-ISOLDE Current REX-ISOLDE

15. Radioactive ISOL beam yields 2020 GANIL-ISOLDE Jan 07 agreement – Complementarity; Collaboration 2016 2012 present

16. projectile Final fragment Excited pre-fragment target hotspot Projectile Fragmentation Reactions Energy (velocity) of beam > Fermi velocity inside nucleus ~30 MeV/u Can ‘shear off’ different combinations of protons and neutrons. Large variety of exotic nuclear species created, all at forward angles with ~beam velocity. Some of these final fragments can get trapped in isomeric states. Main difficulty:- beam is a cocktail of many species Problem 1: Isotopic identification. Problem 2: Isomeric identification.

17. Production of Exotic Nuclei at relativistic Energies

18. J. Benlliure high-energy nucleus Identified by A and Z Production techniques • In-flight fragmentation thin target spectrometer heavy projectile • 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

19. In-flight Fragmentation (and Fission) Fragment Recoil Separator Ge  Answer to our identification difficulty : - FRS  Such Separators exist at MSU, GANIL, RIKEN and GSI  Relativistic energy fragmentation: => heavy ions (GSI unique!) We will look at how it works later.

20. Rare-Isotope Production Target Antiproton Production Target FAIR - Facility for Antiproton and Ion Research GSI today FAIR SIS 100/300 UNILAC SIS 18 ESR Super FRS HESR Nustar three branches RESR CR FLAIR 100 m NESR

21. “Facility for Antiproton and Ion Research (FAIR)” : GSI today FAIR SIS 100/300 UNILAC SIS 18 Rare Isotope Prod.target Super FRS HESR ESR Super FRS RESR CR NESR 100 m

22. For example: DESPEC will have access to some key N=82 and N=126 r-process nuclei

23. high-energy nucleus Production techniques • Gamma/neutron converters(A variant of ISOL scheme) ion source converter thick target mass separator g, n e-, d post-acceleration diffusion • Two-step reaction scheme(ISOL + Fragmentation) fragmentation spectrometer fission ion source mass separator light projectile post-acceleration diffusion J. Benlliure

24. J. Benlliure low-energy nucleus high-energy nucleus Production techniques • In-flight fragmentation thin target gas cell spectrometer heavy projectile • 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

25. Current Schemes for producing beams 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

26. ISOL and In-Flight facilities-Partners It is probably true to say that if we worked at it virtually all experiments could be done with both types of facility but they are complementary. ISOL In-Flight • 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

27. A.Richter, TH Darmstadt

28. What is the structure of nucleonic matter? 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. • 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? • …..???? There are many unanswered questions:

29. Structure of the nucleon and other hadrons The 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? ●…………..?????

30. The role of nuclei in the Universe Goal: to combine our knowledge of nuclear structure and theory with astronomical observations to model astrophysical processes. Many unanswered questions or badly understood 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 • ……????

32. J. Benlliure high-energy nucleus Production techniques • In-flight fragmentation thin target spectrometer heavy projectile • 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

33. In flight fragmentation (and fission) - Fragment Recoil Separator (GSI) Ge Detection setup  First half of spectrometer :-Momentum-to-charge selection plus beam rejection • Second 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

34. Cd Ga S. Pietri et al., RISING data 107Ag beam

35. The Present Rare Isotope Facility at GSI Limitations • Low primary beam intensity (e.g. 108238U /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

36. The Future of this kind of measurement FRS (RISING) to Super-FRS(DESPEC) H. Geissel et al. NIM B 204 (2003) 71 Note:-Super here means superconducting not------

37. Synchrotron

38. 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 > 

39. Synchrotron No RF power -Initial E(i) and p(i) T = 2R = 2RE(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 = ncpc nc; B =pc R E R q

40. SIS 18 at GSI

41. 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.

42. The Super-FRS and its Branches EXL ELISE ILIMA R3B Beam from SIS100/300 NuSTAR- [Nuclear Structure Astrophysics and Reactions] Collaboration