Spin-oriented Radioactive-isotope Beams at RI Beam Factory

1. Spin-oriented Radioactive-isotope Beams at RI Beam Factory H. Ueno RIKEN Nishina Center SPIN2010, Sep/27-Oct/2, 2010

2. RIBF phase I • RIBF • Intense beams over the whole range in the Z number at E=350AMeV to BigRIPS Zero-deg. spectrometer - g spectroscopy SRC fRC IRC Phase I BigRIPS - RIB production

3. BigRIPS Layout Beam dump 1st stage Target 2nd stage Experimental set-ups ZeroDegree: Zero-degree forward Spectrometer T. Kubo, Nucl. Instr. Meth. B204, 97 (2003). T. Kubo et al., IEEE Transactions on Applied Superconductivity, 17, 1069 (2007)

4. GARIS II (~2009) GARIS 5 MeV/nucleon RILAC II (~2010) RILAC fRC BigRIPS + (ZD/SHARAQ) RRC 345 MeV/nucleon IRC SRC 135 MeV/nucleon (AVF) 60 MeV/nucleon (RILAC) RIPS CRIB 15 MeV/nucleon AVF RIBF operation scheme RILAC+RRC+fRC+IRC+SRC RILAC+RRC +IRC+SRC AVF +RRC +SRC

5. SAMURAI - large acceptance SCRIT - e-RI collision Rare RI Ring - mass SHARAQ - high resolution SLOWRI - slow RIBs Phase II RI Spin Laboratory - spin-oriented RIBs RIBF phase I + II • RIBF • Intense beams over the whole range in the Z number at E=350AMeV to BigRIPS Zero-deg. spectrometer - g spectroscopy SRC fRC IRC Phase I BigRIPS - RIB production

6. Nuclear-spin related experiments BigRIPS BigRIPS+SHARAQ

7. Heavy-ion primary beam intensities at RIBF E/A = 345 MeV Pol. d (250 MeV/nucleon) : 30pnA & pol. ~ 80 % (Apr. 2009) 18O (345 MeV/nucleon): 1000 pnA (Jun. 2010)

8. Expected RI-beam intensities at BigRIPS RI-beam intensities will be upgraded very much, so that the accessible region can be enlarged to a large extent. One counts/day limit at BigRIPS @1 pmA Expected yields @ BigRIPS 78Ni ~10 pps (238U) 132Sn ~107 pps (238U) 100Sn ~1 pps (124Xe) I (primary beam) = 1 pA (6x1012 particles/sec) r-process path 78Ni

9. Ground state nuclear moments (β-NMR) • N～20 (RIPS&LISE) • N～28 (RIPS) • Isomeric state nuclear moments (TDPAD) • N～28 (BigRIPS) • A～70 (RIPS) • Two-step fragmentation • Future program • RIPS upgrade (IRC-RIPS transport line)

10. Neutron-rich Al isotopes & island of inversion Island of inversion • Inversion of sd &pfconfiguration around N=20 • Ground-state deformation in spite of N～20 • “Island of inversion” • Anomalously tight binding A∼32 • C. Thibault et al., Phys. Rev. C 12 (1975) 644. • C. Détraz et al., Nucl. Phys. A394 (1983) 378. • Lowering of 21+ excitation energies • C. Détraz et al., Phys. Rev. C 19 (1979) 164. • D. Guillemaud et al., Nucl. Phys. A426 (1984) 37. • Large B(E2) values • T. Motobayashi et al.,Phys. Lett. B 346 (1995) 9. N=20 Neutron-rich Al isotopes • Located just outside the island of inversion • No in-beam gamma-ray spectroscopy data for Al isotopes • (∵ odd-(odd || even) nuclei) • No significant extra binding (small effect?) Theoretical studies Why nuclear moments? • Proposed large scale shell models • Predicted intruder component in the ground states of Al isotopes • The electromagnetic moments would signify the onset of possible evolution in the nuclear structure Ground-state deformation induced by the inversion of normal and intruder states E.K. Warburton et al., PRC41 (1990) 1147. Island of inversion

11. Large scale shell model & neutron-rich Al isotopes Predictions from large scale shell model Predictions from Monte Carlo shell model 31Al 34Al 32Al 33Al 33Al • The decreasing gap energies are predicted for n-rich Al isotopes towards 33Al. • E0p0h-E2p2h > 0 for Al isotopes, but similar behavior to the Mg, Na, and Ne cases • It is predicted that the inversion between 0p-0h and 2p-2h configurations takes place at 33Al for N=20 isotones. E. Caurier et al., PRC58, 2033 (1998) Y. Utsuno et al., PRC 64, 011301(R) (2001)

12. Detector Detector Large-Z target Small-Z target Fragmentation-induced spin polarization Properties: Polarization: f (θ, p) Independent of the chemical & atomic properties Deeply implanted Maximum P～40%, typically P～a few % for NMR setting fragment projectile Sum of the lost Fermi momenta P Position vector of the participant portion R -P Angular momentum left in the fragment part LF=-RxP target K.Asahi et al., PLB 251, 499 (1990) near-side trajectory far-side trajectory Au Au Nb Nb Al 40AMeV 70AMeV 110AMeV 70AMeV 70AMeV H. Okuno et al., PL B335,29 (1994)

13. RIBF Zero-deg. spectrometer - g spectroscopy RIPS SRC fRC IRC Phase I+α SHARAQ - high resolution BigRIPS - RIB production

14. Measurements @RIKEN Method: Polarized RI beam + β-NMR spectroscopy Measured: N=20 stable isotopes μ and/or Q known RIPS Island of inversion μ[30Al] Q [31Al] Q [32Al] β-NMR apparatus μ[32Al] |eqQ/h| (kHz) |eqQ/h| (kHz) H. Ueno et al., PLB 615, 186 (2005) D. Kameda et al., PLB 647, 93 (2007) D. Nagae et al., PRC 79 027301 (2009).

15. μ Ｑ I = 0 g-factor known Recent nuclear-moment measurements now up to 2000 N=20 ISOLDE GANIL RIKEN 23 Al 31 Al 25 Al Aldata (RIKEN, GANIL) From recent experiments G. Huber et al., Phys. Rev. C 18, 2342 (1978) M. Keim et al., Eur. Phys. J. A 8, 31 (2000). G. Neyens et al., Phys. Rev. Lett. 94, 022501 (2005) Island of inversion

16. Detector Detector Large-Z target Small-Z target Fragment-induced spin orientation fragment projectile Sum of the lost Fermi momenta P Position vector of the participant portion R -P Angular momentum left in the fragment part LF=-RxP target K.Asahi et al., PLB 251, 499 (1990) Spin polarization Spin alignment Detector near-side trajectory • Fragments scattered at 0◦ • High energies are suitable because of • production of RIBs • population of isomeric states • production of spin alignment far-side trajectory

17. g-Factor measurements of isomeric states gRISING campaign @GSI around Fe , 43mS @GANIL

18. Spin-aligned RIB @ RIBF • New method to produce spin-aligned PF-based RIBs. • Two-step fragmentation • No projectile dependence

19. AP AF AP AF+1 AF Two-step Fragmentation method • Large number of nucleon-removal → small spin orientation • RIBF standard operation: rare gas + U beams → measurements are limited near rare-gas and U elements Alternatively… Two-step fragmentation method is proposed. Much higher spin alignment can be expected, although production yields are smaller.

20. Dispersion matching Secondary Beam (44Sc) momentum alignment Tertiary Beam (43mSc) Two-step PF + dispersion matching simple two-step PF Y～1/1000* Y1-step dispersion matching two-step PF + dispersion matching Y～1/50* Y1-step

21. Experiment @ BigRIPS Measurement 2 Measurement 1 Measurement 3 Two-step PF w/ Disp. Matcing. Two-step PF w/o Disp. Matcing. One-step PF 48Ca@345MeV/u, 200pnA F0 target : Be 10mm F1slit : ±3% F5 target : Al 10mm (Wedge) (Goldhaberwidth = 0.4%) F5 slit : ±0.5% F7 slit : center±0.15% 48Ca@345MeV/u, 200pnA F0 target : Be 10mm F1 slit : ±3% F5 target : Al 10mm (Wedge) (Goldhaber width = 0.4%) F5 slit : ±3% F7 slit : center±0.15% 48Ca@345MeV/u, 200pnA F0 target : Be 4mm (Energy loss = 3% Goldhaber width = 4%) F1 slit : ±0.5% Japan-France-Burugalia collaboration

22. TDPAD exp for 32mAl

23. Result 2 : two-step vs one-step Measurement 2 Measurement 3 Two-step PF One-step PF preliminary preliminary vs. A < 2% Yield(32Al) ～ 10 kcps (Att.1/100) Yield(gamma) ～ 9 cps 9.3h measurement A ～ 9.3(6)% Yield(32Al) ～ 2.2 kcps @ setup Yield(gamma) ～ 10 cps 8.6h measurement Figure of Merit (～Y・A2) > 20

24. Result 1 : dispersion matching Measurement 1 Measurement 2 w/o dispersion matching w/ dispersion matching p @F3 pcut @F3 p @F5-F7 A2 : Asymmetry param. (0.447 for E2) B2 : rank2 tensor B2 = 1.15*A(A:spin alignment) vs. x@F7 preliminary preliminary A～10.1(11)% A～9.3(6)% Dispersion matching looks fine

25. RIBF • phase-I completed • phase-II in progress • Ground state nuclear moments (β-NMR) • N～20 (RIPS&LISE) • N～28 (RIPS) • Isomeric state nuclear moments (TDPAD) • N～28 (BigRIPS) • A～70 (RIPS) • Two-step fragmentation • Future program (RIBF phase-II) • RIPS upgrade (IRC-RIPS transport line)