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基于放射性束 的核结构、核天体物理研究 刘 忠

基于放射性束 的核结构、核天体物理研究 刘 忠. Outline Brief introduction to RIB physics 100 Sn 区域奇异核衰 变 远 离稳定线核素质量测 量 ( 直 接质子放射性 核 ) Nuclear Detectors R&D for RIB physics Outlook. Rm ∝. 208 Pb. Halo nuclei. Hansen & Jonson , Europhys. Lett ., 1987, 4:409. Halo nuclei.

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基于放射性束 的核结构、核天体物理研究 刘 忠

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  1. 基于放射性束的核结构、核天体物理研究刘 忠 Outline • Brief introduction to RIB physics • 100Sn区域奇异核衰变 • 远离稳定线核素质量测量 • (直接质子放射性核) • Nuclear Detectors R&D for RIB physics • Outlook

  2. Rm∝ 208Pb Halo nuclei Hansen & Jonson, Europhys. Lett., 1987, 4:409. Halo nuclei

  3. Gamow-Teller Strength in its Decay 100Sn: rp process

  4. Shell Model Orbitals

  5. 100Sn GT-strength is unique tool to study wave fct. pure spin-flip transition 0+ => (pg9/2-1 ng7/2)1+ large decay energy => most of GT strength in b-decay window Shell model Grawe et al. measure: T1/2 b-endpoint energy (branching) => GT-strength

  6. Gamow-Teller Strength in its Decay Search for its Isomer 100Sn: rp process

  7. Gamow-Teller Strength in its Decay Search for its Isomer Particle Stability of Neighbours: key to the rp-process 100Sn: rp process

  8. key to the astrophysical rp-process

  9. 100Sn history

  10. the FRagment Separator (FRS) F4 F2 ~109 s-1 ΔE 1st Bρ separation 2nd Bρ separation identification F2-F4: DE => Z Br(x,x´,a´) = b gA/q m0c q = Z TOF => b

  11. the FRagment Separator (FRS) ~109 s-1

  12. 259 100Sn s = 6pb 103Sb? 99Sn 97In 93Ag 95Cd 100Sn setting (full statistics, 15 days) Z N=Z N=Z+1 N=Z+2 N=Z-1 Te Sb Sn In Cd Ag A/Q

  13. Silicon Implantation Detectorand Beta AbsorberSIMBA 7 x-strips 7 x-strips 10 SSSD 60x40x1 mm3 10 SSSD 60x40x1 mm3 100Sn 3 DSSD 60x40x0.7 mm3 Gassiplex+ Mesytec X SSSD 60x60x0.3 mm3 Y SSSD 60x60x0.3 mm3 R - chain pixels in implantation zone: 3x60x40 = 7200

  14. Implantation RISING SIMBA DEGRADER

  15. and how it looks in reality 100Sn

  16. RISING + 15 x 7 Germanium detectors ePhoto~ 11% @ 662 keV

  17. Correlation of Implantation and Decay require same position within ± 1mm in x,y,z record all decay triggers within 15 s (b+ of 3 generations) Maximum Likelihood analysis varying the 100Sn half-life with known: daughter decays, efficiencies, dead times, background T1/2 = 1.16 ± 0.20 s Comparison: MSU 2007 0.55 s GSI 1997 0.94 s 100Sn only 1st decays +0.70 -0.31 +0.54 -0.26

  18. Gamma Spectrum after Beta Decay of 100Sn all events within 4 s after implantation 141 511 436 96 141 436 1297 2048 96

  19. what do we expect? Stone, Walters 1985 2003 g intensities corrected for efficiency and M1 conversion 511 (pg9/2)-1ng7/2 111 total b+ decays 70 100Sn b+ decays (pg9/2)-1nd5/2 Gamma Intensities 5 lines add up to 4018 keV ???

  20. E*(1+) = (2.71 + x) MeV with x ≈ 0.05 MeV • because: • total sum energy = 2.76(0.43) MeV (Schneider et al.) • DMc2- QEC(1+)= 2.6(1.0) MeV (Chartier et al.) • one b-delayed proton event: • Ep + Sp(100In) = 2.93(0.34) MeV (Audi et al.)

  21. compare to shell model Grawe et al. Nowacki, Sieja

  22. Extraction of Beta Spectrum sum over total energy within 3 s after implantation in implantation zone + calorimeter tested (by eye) for uninterrupted tracks from maximum likelihood Emax = 3.29 ± 0.20 MeV QEC = 4.31 ± 0.20 MeV to excited state => I(b+)= 87% => log ft = 2.62 100Sn b spectrum conv. line? result of ML analysis +0.13 -0.19 range of analysis

  23. superallowed GT 100Sn known log(ft) values Nuclear Data Sheets 84 (1998) 487 log (ft)

  24. Decay of the heaviest N=Z doubly magic nucleus 100Sn

  25. Gamow Teller Strength GT strength of even Sn isotopes extreme SM SM truncated QRPA FFS exp. A. Bobyk, W. Kaminski, I. Borzov 2000 H. Grawe, 2010

  26. why is BGT that large? wave functions must be rather pure I i > = {(pg9/2)10} 0+ < f I = {(pg9/2)9 (ng7/2)1} 1+ 10 protons can transform into a neutron

  27. Conclusions the 100Sn shell gap is robust - doubly magic -

  28. 5 4 Eg/MeV 3 3 isomer decays after ToF=200ns decaying within 25 ns ? 2 1 T/ms 0 15 5 20 10 6+ isomer in 100Sn ? Eg/MeV

  29. what‘s new? 103Sb T1/2 < 50 ns ! 99Sn T1/2 > 0.2 ms 97In 95Cd 93Ag

  30. Conclusions • first observation of 93Ag, 95Cd, 97In, and 99Sn • reduced rate of 103Sb => T1/2 < 50 ns • 102Sn: new isomeric state • 100Sn: probably no isomer • 1stg-spectrum after decay of 100Sn • 100Sn decay: T1/2, Ebmax, Eg, BGT • superallowed GT transition • => dominant configurations (pg9/2)10 =>(pg9/2)9 (ng7/2)1

  31. The 100Sn Team photo taken by Hans Geissel

  32. Study of N ≥Z proton drip-line nuclei 96,97,98Cd with astrophysical consequencesSpokespersons: A. Blazhev, P. Boutachkov Z. Liu, R. Wadsworth • Shell structure near doubly-magic 100Sn • Abundance of isomeric states • Exotic decay mode

  33. Neutron-proton pairing T=1, S=0 T=0, S=1 Tz=0

  34. N=Z nuclei, unique systems to study np correlations T=0 Pairing may become Important in A>80 N=Z nuclei A. L. Goodman , PRC 60, 014311 (1999) Experimental signals for T=0 np pairing Binding energy differences Deutron transfer reactions  Rotational properties: delayed alignments in N=Z nucl Level structure: 92Pd, B. Cederwallet al.Nature 469, 68-71 (2011) Spin-gap isomer: 96Cd

  35. E6 Spin gap T=0 T=0 No T=0 96Cd Effect of T=0 np interaction in 96Cd Shell model calculations by H. Grawe

  36. Z A/Q RISING S352 Experimental Setup Stopped RISING Primary beam 124Xe @ 850 MeV/u Active stopper 96Ag

  37. 0.27(14) s new known: R. Grzywacz et al. PRC 55 (1997) 1126 B(E4; 19+ 15+) = 0.4(3) W.u. 4168 Counts SE 4264 B(E2; 19+ 17+) = 4(3) W.u. E[keV] 1.58(3) s 78(8) s B(E3; 13- 10+) = 0.187 (20) W.u. 96Ag Tf<1 s

  38. T1/2 (421) = 0.67  0.15 s(96Cd g.s.) 96Cd  T1/2(470, 1506, 667) = 0.29-0.10 + 0.11 s 0-0.2 μs 0.2 – 4.5 μs 96Cd 0.2 – 4.5 μs

  39. Effect of iso-scalar np interaction in 96Cd, 16+ isomer E6 Spin gap

  40. Beta decay GT strengths in GF space 100% g9/2 → g9/2, similar to the case of g9/2 → g7/2 seen in 100Sn 16+ 15+ BGF = 0.14 with quenching factor of 0.6 (Herndl and Brown NPA627, 35 (1997)) Bexp= [3860(18) *  ] / (f T1/2) = 0.19 + 0.08-0.07 with T1/2 = 0.29 secs

  41. 96Cd ResultsB. S. Nara Singh, Z. Liu et al. ,Phys. Rev. Lett. 107, 172502 (2011) • Evidence for the existence of the 16+ E6 “spin-gap” isomer in 96Cd • Evidence for the strong influence of the iso-scalar neutron-proton interaction • Our work allows to deduce T1/2 = 0.67 ± 0.15 s for the g.s. in 96Cd

  42. Results in other nuclei • -decaying high-spin isomers were observed in • 94Pd • 96Ag • 98Cd • Core-excited states aross the N=Z=50 shell closure • identified in 96Ag • more in 98Cd • Phys. Rev. C 82, 061309(R)(2010) • Phys.Rev. C 84,044311 (2011) • J.Phys.:Conf.Ser. 205, 012035 (2010)

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