Nuclear Structure Studies along the Z=28 and 82 Closed Proton Shells using Radioactive Ion Beams

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Nuclear Structure Studies along the Z=28 and 82 Closed Proton Shells using Radioactive Ion Beams Piet Van Duppen Instituut voor Kern- en Stralingsfysica K.U. Leuven, Belgium 1.

1 Nuclear Structure Studies along the Z=28 and 82 Closed Proton Shells using Radioactive Ion Beams Piet Van Duppen Instituut voor Kern- en Stralingsfysica K.U. Leuven, Belgium 1. Radioactive Ion Beam Production 2. Instrumentation and tools 3. The Z=28 region: testing shell model descriptions 4. The Z=82 region: testing mean field descriptions K.U. Leuven

1. Radioactive Ion Beam Production Production of radioactive ion beams: Isotope Separator On Line (ISOL) versus In-Flight (IF) ISOL and Post Acceleration Production Ionization Post Acceleration The

2 1. Radioactive Ion Beam Production Production of radioactive ion beams: Isotope Separator On Line (ISOL) versus In-Flight (IF) ISOL and Post Acceleration Production Ionization Post Acceleration The Euroschool Lectures on Physics with Exotic Beams, Vol. I, II and III In-Flight Separation of Projectile Fragments D.J. Morrissey and B.M. Sherrill Isotope Separation On Line and Post Acceleration P. Van Duppen Lecture Notes on Physics 651 (2004), 700 (2006) and 764 (2008), Springer Verlag Berlin H.L. Ravn and B.W. Allardyce: On-Line Mass Separators Treatise on Heavy Ion Science, vol. 8 (1989) 363 EMIS conferences: Nucl. Instr. Meth. B204 (2003), Nucl. Instr. Meth. B266 (2008)

3 Far from Stability Conference (*), Lysekil, Sweden (1966) What are the limits for the existence of nuclei? How does the nuclear force depend on the proton-toneutron ratio? How can collective phenomena be explained from individual motion? Is it possible to explain complex nuclei on the basis of simple building blocks? What is the origin of the elements. Z Research with exotic nuclei (extreme N/Z ratio) Nuclear-Structure Physics Nuclear Astrophysics Fundamental Interactions Applications Theory and Experiment N (*) the mother of the ENAM conferences Radioactive Ion Beams - RIB

4 thin target fragment separator GeV/u µs In Flight (IF) storage ring In-Flight versus ISOL heavy ions -fusion -fragmentation driver accelerator reactor gas cell Isotope Separator On Line (ISOL) light ions, neutron, electrons -spallation high-temperature thick target -fission -fragmentation ion source mev (rest) 20 MeV/u ~ ms to s mass separator post accelerator experiment complementary D.J. Morrissey and B.M. Sherill, In-flight Separation of Projectile Fragments Euroschool on Exotic Nuclei Lecture Notes on Physics 651 (2004) 113, Springer Verlag Berlin

5 Radioactive Ion Beam Production High production rate: cross section is a nature given number optimize beam/target combination available beams (accelerators, reactors) power deposition in targets Efficient: production rate of very exotic nuclei is always small Fast: exotic nuclei have often short half lives Selective: in most cases, unwanted contaminants are produced in copious amounts maximize Intensity Selectivity Sensitivity

6 transfer line catcher production target primary beam proton 1-1,4 GeV ion source analyzing magnet cooler charge state breeder secondary beam control room post accelerator experimental hall experiment

7 Production of radioactive nuclei: ex. 1 GeV proton on 238 U spallation fission fragmentation

8 1 GeV proton beam on a La target unselective Production rate (a.u.) Sn Need for selective ion source Note the radioactive inventory Z=50 Sn J. Lettry, V. Fedoseev (CERN) Mass separation

9 I reaction products = σ N Φ target cross section [barn] number of target atoms/surface [barn -1 ] primary beam flux [s-1] 74 Zn (Z=30) Ga (31) X Example: 1 GeV protons on 238 U (UC target, 52 g/cm 2 ): 80 Zn: σ = 0,01 mbarn, 2 µa protons Primary production rate: 1, pps I M. Bernas et al., Nucl.Phys. A (2003) - GSI secondary beam delay = I reaction products ε = ε. ε. ε. ε. ε. ε. ε ion transport cool bunch breeding acceleration Note: ε i 1

10 Delay losses in target and ion source: Delay-time distribution P(t): P(t)dt = probability for an atom of a given element created at t=0 to be released from the source between t and t+dt (not dependent on the half life!!) Efficiency for survival against radioactive decay: P t λ exp( λ t) ε ( ) ( ) delay 1/ 2 T = P t exp( λt)dt = εdelay ( T1/ 2 ) = T1/ 2 ( T1/ 2 + Tdelay ) e.g.: ( ) delay delay 0 Release Ga simulation experiment ion beam ionizing cavity Monte Carlo simulations Time (s) short proton beam pulse at t=0 s proton beam target container H. Ravn, The EURISOL report, 2003 Release Sn simulation experiment Time (s)

11 heavy ion GSI: thin target 1 R. Kirchner, NIMB70 186, ε delay Efficiency.ε ion Ag Xe Xe T delay =10 s Bi Sn Sn Ne Bi Xe Kr Ar ISOLDE: thick target (50 g/cm 2 ) T 1/2 (s) Ionization efficiency for long-lived isotopes (ε ion ) S. Lukic et al. NIMA565 (2006) 784 large target volume! Different Fr isotopes with different half lives

Ionization 60kV of radioactive nuclei: Resonant photo ionization extraction electrode target x ionizer cavity + some V - Many different ionization mechanisms: surface ionization

12 Ionization 60kV of radioactive nuclei: Resonant photo ionization extraction electrode target x ionizer cavity + some V - Many different ionization mechanisms: surface ionization electron impact ionization (plasma sources) laser ionization Efficiencies: ε ion ~ 1 50 % Physical and chemical properties of the elements: e.g. cold transfer line, molecular beams

13 ISOLDE laser ion source operation in h ~ 2000 h 1763 h Hours Year about 50 % of RIB produced using lasers!!!

14 H Li Na Be Mg Cs Rb K Fr Ba Sr Ca Ra La Y Sc Ac Hf Zr Ti Rf Ta Db W Sg Re Bh Os Hs Ir Mt Pt Ds Au Rg Hg 112 Al Tl Si Pb P Bi S Po Cl At Nb V Mo Cr Tc Mn Ru Fe Rh Co Pd Ni Ag Cu Cd Zn In Ga Sn Ge Sb As Te Se I Br Xe Kr Ar Rn B C N O F Ne He Th Ce Pa Pr U Nd Np Pm Pu Sm Am Eu Cm Gd Bk Tb Cf Dy Es Ho Fm Er Md Tm No Yb Lr Lu + SURFACE hot PLASMA cooled LASER ION SOURCE:

15 Mass separation: mass resolving power: M/ M FWHM M/ M ~1500 Relative intensity Mass Energy spread of the ion beam due to collisions with the rest gas Slits: at A=205, 1% of A=208 is present

16 RFQ-Trap/Cooler Switchable Electrodes Ions Buffer Gas Ions RFQ Segments UDC 10 mm Accumulate End Plate Laser Ions Release SIMION 7.0: simulation of the potential distribution Z

17 angle distance

18 to experiments from HRS (60KeV)þ differential pumping

19 shielding!!! Jura mountains

20 Proton beam target unit robot

21 target container 20 cm Proton beam target container neutron converter 1.4 GeV proton p per pulse p-pulse every 1.2 s I av = 2 µa

So far >600 radioactive isotopes of >60 elements @ 60

22 So far >600 radioactive isotopes of >60 60 kev Need for higher energy radioactive ion beams: REX-ISOLDE

23 1.4 GeV, 2 µa Post-acceleration of ISOLDE beams (from 60 kev to 3.1 MeV/u) proposed 1995: new concept to accelerate all existing ISOLDE beams first physics experiment 2002

24 Charge-state breeding EBIS Target Stations acceleration Mass separator R ~ 1/150 RFQ: 300 kev/u IHS: MeV/u 7 gap and 9 gap: 3 MeV/u Penning Trap cooling bunching

REX-ISOLDE OVERVIEW Nier-spectrometer Select the correct A/q and separate the

A/q resolution ~150 EBIS Super conducting solenoid, 2 T Electron beam < 0.

5 Optional stripper MASS SEPARATOR REXEBIS ISOLDE 9-GAP RESONATOR 7-GAP

Experiments Linac 3.0 MeV/u 2.2 MeV/u 1.2 MeV/u Length 11 m Freq.

2-3MeV/u A/q max. 4.5 (2.2MeV/u), 3.5 (3MeV/u) 0.

25 REX-ISOLDE OVERVIEW Nier-spectrometer Select the correct A/q and separate the radioactive ions from the residual gases. A/q resolution ~150 EBIS Super conducting solenoid, 2 T Electron beam < 0.4A 3-6 kev Breeding time 3 to >200 ms Total capacity charges A/q < 4.5 Optional stripper MASS SEPARATOR REXEBIS ISOLDE 9-GAP RESONATOR 7-GAP RESONATORS IH RFQ Rebuncher ISOLDE beam Primary target High energy driver beam Experiments Linac 3.0 MeV/u 2.2 MeV/u 1.2 MeV/u Length 11 m Freq. 101MHz (202MHz for the 9GP) Duty cycle 1ms 100Hz (10%) Energy 300keV/u, 1.2-3MeV/u A/q max. 4.5 (2.2MeV/u), 3.5 (3MeV/u) 0.3 MeV/u REXTRAP 60 kev protons REX-trap Cooling (10-20 ms) Buffer gas + RF (He), Li,...,U 10 8 ions/pulse (Space charge effects >10 5 ) Didier Voulot Total efficiency : 1-10 %

26 20,0 15,0 27Al Efficiencies for beams 2006 Tot. eff. = Trap BTS EBIS Sep % 10,0 116Cd 5,0 7Li 238U 0, A Original scope of REX-ISOLDE: efficiency ~ 10%, A < 50

27 MINIBALL

28 80 Zn (T 1/2 =0.54 s) Primary production in target: ~1, pps 60 kev beam: pps delay: ~ 1-4 % ionization: ~ 4-1 % Accelerated beam on target: pps cooling-bunching-breeding-acceleration efficiency ~5 %

1. Radioactive Ion Beam Production Radioactive ion beam production using ISOL method Production, release, ionization, mass separation, acceleration: sensitive, selectivity, intensity Ion beam

29 1. Radioactive Ion Beam Production Radioactive ion beam production using ISOL method Production, release, ionization, mass separation, acceleration: sensitive, selectivity, intensity Ion beam manipulation: resonant laser ionization, RF-cooling, time structure Realistic example: 80 Zn (Z=30, N=50) ENERGY: Energy upgrade to 10 MeV/u and lower energy capacity INTENSITY: ISOLDE proton driver beam intensity upgrade strongly linked to PS Booster improvements including linac4 QUALITY: ISOLDE radioactive ion beam quality: broader spectrum and higher quality (purity, emittance, time structure)

Present ISOLDE facility Aims of HIE-ISOLDE upgrade First steps towards HIE-ISOLDE

The HIE-ISOLDE ISOLDE Project Alexander Herlert, CERN Present ISOLDE facility Aims of HIE-ISOLDE upgrade First steps towards HIE-ISOLDE Hirschegg Workshop 2008 B. Jonson s talk at the last ISOLDE workshop