1. Overview of the Search for New Isotopes and New Isomers at RIKEN RI Beam Factory T. Kubo, RIKEN Nishina Center Presented on June 4, 2013 @INPC2013 conference, Palazzo dei Congressi, Firenze, Italy, June 2-7, 2013 expand accessible regions of exotic nuclei BigRIPS separator

2. Layout of RI Beam Factory (RIBF) E ~350 MeV/u up to U Goal intensity 1 p  A  Major features of BigRIPS separator Large acceptances Comparable with the spreads of in-flight fission of 238 U Two-stage separator scheme with excellent particle identification (PID) PID scheme based on TOF-B  -  E method with track reconstruction  Z and A/Q A/Q resolution is high enough to identify charge state events A new-generation in-flight RI beam facility

3. 50 82 126 50 4040 2020 28 6060 7070 N Z  Proton-rich isotopes using projectile fragmentation of 124 Xe at 345 MeV/u Dec. 2011 (~9 pnA) 124 Xe r-process path  Neutron-rich isotopes using in-flight fission of 238 U at 345 MeV/u May 2007 (~0.007 pnA, 4 x 10 7 pps) Nov. 2008 (~0.22 pnA, 1 x 10 9 pps) Oct. 2011 (~0.5 pnA, 3 x 10 9 pps) Fall 2012 and spring 2013 (~10 pnA) during EURICA campaign 238 U Search for new isotopes and new isomers that has been performed since 2007 By using BigRIPS separator at RIBF

4. TOF B  B  TOF, B ,  E  Z, A/Q Target PPAC x2 Plastic PPAC x2 Plastic Isomer setup RI beam Plastic Al stopper or Si stack CsI(Na) Clover-Ge X 3 or 4 Isotope separation: F1 degrader/stripper + F5 degrader Degrader/stripper Degrader  IC PPAC x2 MUSIC Experimental setups 2008 2011 2007 Standard beam-line detectors at BigRIPS for TOF, B ,  E measurement for PID Clover-type Ge detectors for isomer measurement BigRIPS ZDS

5. 238 U 86+ + Be at 345 MeV/u 2007 U experiment I ~0.007 pnA (4 x 10 7 pps ) 123 Pd 125 Pd known Running time: ~1 day First experiment at RIBF! 125 Pd(new) 126 Pd(new) Two new isotopes 125 Pd and 126 Pd identified! T. Ohnishi et al.: J. Phys. Soc. Jpn. 77 (2008) 083201. ( demonstrated the potential of BigRIPS)

6. Setting 1 Z~30Setting 2 Z~40Setting 3 Z~50 2008 U experiment 238 U + Be 238 U + Pb Unknown Enlarged plots  3 different settings 238 U + Be/Pb 345MeV/u  ~30 times larger intensity than in 2007 ~0.22 pnA (1 x 10 9 pps) T. Ohnishi et al.: J. Phys. Soc. Jpn. 79 (2010) 073201. 45 new isotopes in a wide range of neutron-rich exotic nuclei!

7. 2011 U experiment Setting1 Z~59 Setting2 Z~64 Z A/Q 238 U 86+ + Be at 345 MeV/u Unknown ~0.5 pnA (3 x 10 9 pps) Preliminary! 14 new isotopes (preliminary) Z~60 region 124 Xe experiment 124 Xe + Be at 345 MeV/u ~9 pnA Preliminary! Search for proton drip-line isotopes in Z~40-50 region

8. 2008 U experiment 18 2011 U experiment Preliminary! 19 Delayed  -ray spectra from new isomers

9. New isotopes 2011 (14) New isotopes 2008** (45) New isotopes 2007* (2) New isomers 2011 (19) New isomers 2008*** (18) 238 U: ~0.5 pnA 238 U: ~0.22 pnA 238 U: ~0.007 pnA New isotopes: 65 New isomers: 37 60 7070 4040 5050 82 126 3030 **T. Ohnishi, T. Kubo et al.: J. Phys. Soc. Jpn. 79 (2010) 073201. *T. Ohnishi, T. Kubo et al.: J. Phys. Soc. Jpn. 77 (2008) 083201. ***D. Kameda, T. Kubo et al.: Phys. Rev. C 86 (2012) 054319. New isotopes 2011 (4) 124 Xe: ~9 pnA Summary of the results r-process path

10. 60 68 75 132 Sn 78 Ni 34 Overview of isomer measurements in 2008 U experiment  A variety of spectroscopic information in a very wide range of neutron-rich exotic nuclei  Proposed level schemes and isomerism  Investigated the evolution of nuclear structure See D. Kameda et al: Phys. Rev. C 86 (2012) 054319. Spherical isomer: seniority isomer Spherical isomers: seniority isomer and spin-gap isomer Spherical isomers due to shell evolution - N~75 region: never studied before - New deformed region? - Shape isomers due to shape coexistence - N~68 region: a variety of nuclear shapes (prolate, oblate, triaxial) and coexistence - Shape isomers, K-isomer, etc. - N~60 region: famous for shape coexistence - Several new isomers including shape isomers - Investigate the evolution of shape coexistence

11. Spherical isomer Shape isomer spherical prolate-def. spherical K-isomer Shape isomer prolate- def. Low-E isomer or Shape isomer oblate-def. or prolate-def. Low-E isomer prolate-def. + tirax. Spherical isomer Shape isomer Spherical isomer (Shape isomer) prolate-def. Level schemes and isomerism we proposed

12. 9293949596979899100101102103104105 67 159Ho160Ho161Ho162Ho163Ho164Ho165Ho166Ho167Ho168Ho169Ho170Ho171Ho172Ho 66 158Dy159Dy160Dy161Dy162Dy163Dy164Dy165Dy166Dy167Dy168Dy169Dy170Dy171Dy 65 157Tb158Tb159Tb160Tb161Tb162Tb163Tb164Tb165Tb166Tb167Tb168Tb169Tb170Tb 64 156Gd157Gd158Gd159Gd160Gd161Gd162Gd163Gd164Gd165Gd166Gd167Gd168Gd169Gd 63 155Eu156Eu157Eu158Eu159Eu160Eu161Eu162Eu163Eu164Eu165Eu166Eu167Eu168Eu 62 154Sm155Sm156Sm157Sm158Sm159Sm160Sm161Sm162Sm163Sm164Sm165Sm166Sm167Sm 61 153Pm154Pm155Pm156Pm157Pm158Pm159Pm160Pm161Pm162Pm163Pm164Pm165Pm166Pm 60 152Nd153Nd154Nd155Nd156Nd157Nd158Nd159Nd160Nd161Nd162Nd163Nd164Nd 59 151Pr152Pr153Pr154Pr155Pr156Pr157Pr158Pr159Pr160Pr161Pr162Pr163Pr 58 150Ce151Ce152Ce153Ce154Ce155Ce156Ce157Ce158Ce159Ce160Ce Preliminary! Er Overview of isomer measurements in 2011 U experiment NewKnown Observed isomers 19 new isomers in Z~64, N~100 region! 100 64 It is predicted that nuclei in this region exhibits large prolate-deformation. Moller et al., Nucl. Data.Tables 59, 185 (1995) Interpretation of nuclear isomerism is still going on. Some of new isomers have been interpreted as a high K-isomer. Visit posters by S. Go et al. and by R. Yokoyama et al. for details 170 Dy Known, not observed

13. Regions studied in recent EURICA campaign at RIBF decay measurements for very neutron-rich exotic nuclei using a Ge ball 238 U 345 MeV/u ~10 pnA New isotopes discovered 2013 Spring campaign 2012 Fall campaign EURICA (EUROBALL RIKEN Cluster Array)

14. Summary The results of search for new isotopes and new isomers using BigRIPS separator at RIKEN RI Beam Factory (RIBF) have been reviewed. The region of accessible exotic nuclei is expanding at RIBF with increasing beam intensity (e.g. ~10 pnA 238 U) and the research on exotic nuclei is being promoted. Year 238U Intensity in pnA Planned schedule of intensity upgrade at RIBF From RIKEN accelerator group

15. 2007 experiment collaboration

16. 2008 experiment collaboration

17. RIKEN Nishina Center, Japan T. Kubo, N. Inabe, N. Fukuda, H. Takeda, D. Kameda, H. Suzuki, K. Yoshida, K. Kusaka, K. Tanaka, Y. Yanagisawa, M. Ohtake, H. Sato, Y. Shimizu, H. Baba, M. Kurokawa, D. Nishimura, T. Ohnishi Center for Nuclear Study (CNS), University of Tokyo, Japan S. Go, R. Yokoyama, T. Fujii, E. Ideguchi Tohoku University, Japan A. Chiba, T. Yamada, N. Iwasa Rikkyo University, Japan D. Murai, K. Ieki Kochi University of Technology, Japan S. Momota Osaka University, Japan, H. Nishibata NSCL/MSU, U.S.A. O. B. Tarasov, D. J. Morrissey, B. M. Sherrill Seoul University, South Korea J. Hwang, S. Kim, Y. Sato LPSC-IN2P3, France G. Simpson 2011 238U-experiment collaboration (Oct. 2011)

18. RIKEN Nishina Center, Japan T. Kubo, N. Inabe, N. Fukuda, H. Takeda, D. Kameda, H. Suzuki, K. Yoshida, K. Kusaka, K. Tanaka, Y. Yanagisawa, M. Ohtake, H. Sato, Y. Shimizu, H. Baba, M. Kurokawa, D. Nishimura Center for Nuclear Study (CNS), University of Tokyo, Japan S. Go, R. Yokoyama, T. Fujii, E. Ideguchi Tohoku University, Japan A. Chiba, Y. Okoda, N. Iwasa Rikkyo University, Japan D. Murai, K. Ieki Kochi University of Technology, Japan S. Momota Osaka University, Japan, H. Nishibata GANIL, France M. Lewitowicz, G. de France, I. Celikovic TU-Munchen, Germany K. Steiger NSCL/MSU, U.S.A. D. Bazin, O. B. Tarasov, D. J. Morrissey, B. M. Sherrill 2011 124Xe-experiment collaboration (Dec. 2011)

19. Thank you for your attention.

21. Present RIBF layout F0-F11: 125.983m High-resolution beam line ZeroDegree SHARAQ BigRIPS by CNS  Maximum energy is ~350 MeV/u for heavy ions up to U ions.  Goal beam intensity is 1 p  A (6 x 10 12 particles/sec). Max. beam power ~100 kW SAUMURAI

22.  Large acceptances Comparable with spreads of in-flight fission at RIBF energies: ±50 mr, ±5 % Parameters:  = ±40 mr  = ±50 mr  p/p = ±3 % B  = 9 Tm L = 78.2 m STQ1-14: superconducting Q triplets D1-6: R.T. dipoles (30 deg) F1-F7: focuses Layout and major features of BigRIPS separator From SRC  Superconducting quadrupoles having a large aperture STQ Pole-tip radius= 17cm, pole tip field= 2.4-2.5T Superferric Q Production & separation Particle identification & two-stage separation 1 st stage Wedge Two-stage separator 2 nd stage  Two-stage separator scheme  2 nd stage with high resolution Excellent particle identification without measuring TKE  PID including charge states

23. Particle identification scheme at BigRIPS TOF-B  -  E method with track reconstruction Measure TOF, B ,  E @ 2 nd stage Z, A/Q + isomeric  -rays PID without measuring TKE 1 st stage2 nd stage Wedge  Improve B  and TOF resolution TOF:  Plastic scinti. B  with track reconstruction PPAC x2  E: MUSIC, Si Isomer  -ray: Ge  35, B    57, B  

24. 1 st stage Wedge 2 nd stage Wedge (energy loss) TOF 37 X 3,  3 X 5,  5 X 5,  5,  E Particle identification TOF-B  -  E method with track reconstruction TOF, trajectories (B  ),  E  Z, A/Q TOF 37 = L 35 /  35 c + L 57 /  57 c B  35 /B  57 = (  ) 35 /(  ) 57  determination by the simultaneous equations  35 (1 st half),  57 (2 nd half) X 3,  3 & X 5,  5 B  determination by track reconstruction B  35 X 5,  5 & X 7,  7 B  57 Ion optics 1 st half: 2 nd half:  35, B    57, B  

25. U+Be 2.9 mm B  01 = 7.990 Tm F1 deg Al 2.18mm  P/P =+-3% Z vs. A/Q plot 109 Zr 39+ 108 Zr 39+ 107 Zr 39+ 106 Zr 39+ 109 Zr 40+ 110 Zr 40+ 111 Zr 40+ A/Q spectrum for Zr isotopes (Z=40) A/Q 112 Zr 40+ r.m.s. A/Q resolution: 0.035 % High enough to well identify charge states of fragments G3 setting in J. Phys. Soc. Jpn. 79 (2010) 073201. Excellent particle identification (PID) power for fission fragments TOF-B  -  E method with track reconstruction

26. New isotopes 2011 New isotopes2008 New isotopes 2007 238 U: ~0.5 pnA 238 U: ~0.22 pnA 238 U: ~0.007 pnA New isotopes 2011 124 Xe: ~9 pnA Summary of search for new isotopes Neutron rich: 61 Proton rich: 4 60 7070 4040 3030

27. Runs 238 U intensityNew isotopesNew isomers May 2007~0.007 pnA (4 x 10 7 pps) 2 : 125 Pd, 126 Pd *None Nov. 2008~0.22 pnA (1 x 10 9 pps) 45 : Mn(Z=25) ~ Ba(Z=56) **18 : Z=22~47 *** Oct. 2011~0.5 pnA (3 x 10 9 pps) 14 : Z =56~6019 : Z =59~66 ~10 pnA during EURICA campaign (Fall 2012 and Spring 2013) **T. Ohnishi, T. Kubo et al.: J. Phys. Soc. Jpn. 79 (2010) 073201. *T. Ohnishi, T. Kubo et al.: J. Phys. Soc. Jpn. 77 (2008) 083201. ***D. Kameda, T. Kubo et al.: Phys. Rev. C 86 (2012) 054319. Results using in-flight fission of a 238 U beam at 345 MeV/u Results using projectile fragmentation of a 124 Xe beam at 345 MeV/u 2011 Dec. ( 124 Xe) ~9 pnA 4 : Z =41~44 none