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11 Be@RIBLL Experiment June 2012

11 Be@RIBLL Experiment June 2012. PKU Group + Lanzhou Group. 名称： 12Be 激发态集团结构研究。 内容： 1. 11 Be@MuNCoS calibration ； 2. 12 Be Cluster structure in excited state. Beams applied. 18 O 8+ 70MeV/A 200enA~320enA 初级靶： 9Be 4527um 降能片： 2759um Al. Beam time. 约 11 天 260 小时.

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11 Be@RIBLL Experiment June 2012

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  1. 11Be@RIBLL ExperimentJune 2012 PKU Group + Lanzhou Group

  2. 名称：12Be激发态集团结构研究。 • 内容： 1. 11Be@MuNCoS calibration； 2. 12Be Cluster structure in excited state

  3. Beams applied 18O8+ 70MeV/A 200enA~320enA 初级靶：9Be 4527um 降能片：2759um Al

  4. Beam time 约 11天 260小时

  5. MuNCos实验测试 初级束: 18O8+ 70A MeV 200enA~320enA 初级靶: 9Be 次级束: 11Be@37A MeV，~104 pps, 纯度 ~90%, 到靶上能量：33A MeV 次级靶: 4mm Pb, 200um Pb, 空靶 y z 50cm

  6. 1. 11Be@MuNCoS calibrationMethod establishedH.B. You et al.

  7. 粒子鉴别图 • 0度望远镜粒子鉴别图 • MuNCoS打火数为1，n探测单元阈值：6MeVee • 右图加入中子能量选择，中子能量选择30-40MeV • 0度望远镜挑选出10Be

  8. 与10Be符合后的中子能谱

  9. 2. 12Be Cluster structure inexcited statesZ.H. Yang et al.

  10. 12Be:Generalized Two-Center Cluster model (GTCM) calculation [PRL100(08)182502 ,PRC85(12)044308] S↑ S↑ AO orbit MO orbit AO orbit

  11. Conflicting results for 12Be* GANIL Ref1 Freer MSU Ref2 Charity 4He+8He，with P 4He+8He，with C 6He+6He,CH2 Ref1: PRL82(99)1383 Ref2: PRC76(2007)064313

  12. GANIL exp. M.Freer et al. (PRL-1, PRC-1) PRL82(99)1383 12Be, 31.5 MeV/u, 2 x 104 pps, C target, 10 mgcm-2; （CH2）n ,20 mgcm-2. 10 telescopes; each with 500 um-thick 5 x 5 cm2 DSSD 2 mm strip, 20-240 Lab around the beam line. measuring: 6He+6He; 4He + 8He; reconstruct Ex PRC63(01)034301 the same exp. As above. 10Be and 12Be breakup fragments, no neutron detection.

  13. 12Be + C, MSU exp. • MSU exp., R.J. Charity et al. (PRC-2) PRC76(07)064313 12Be, 50 MeV/u, 105 pps, C target 0.4 mm, CH target 1 mm. beam spot 1 cm x 2 cm 16 HERA telescopes: 2.70-24.80 DSSD(1.5mm thick, 2mm strip) + CsI + 4 LASSA: 29.40-61.50; DSSD(0.5 mm thick, 3mm strip) + CsI very much contradicting GANIL exp. (Freer et al) PRC78(08)054307 the same exp. As above decay to 3H, xLi etc.

  14. Detector Setup PPAC2 DSSD PPAC1 DSSD SSD Target 32.3cm CsI Array 40cm Beam： 12Be，31.8MeV/u，~3000pps Target：Carbon, 100 mg/cm2 DSSD：32 2mm-stip,300μm , CsI：2.5cm*2.5cm*3cm, 5.8cm 13.5cm 15.5cm 18.8cm

  15. Particle Identification 8He ΔE 6He 4He E

  16. Excitation Energy 2-xHe events for 12Be

  17. Detection effeciency Erel resolution(σ) 12Be->4He+8He 12Be->4He+8He

  18. Excitation Energy---4He+4He 107.6KeV 8Be(g.s) 504.1KeV: 9Be->8Be(2+) Ref1 Ref1:PLB580(04)129-14Be breakup

  19. Excitation Energy---6He+6He

  20. ◊4He(12Be,6He+6He)----Saito et al,NPA738(04)337) -----angular distribution analysis L=0 L=2

  21. GANIL exp@1999 (PRL82(99)1383) Intercept: 10.8MeV Slope: 0.15MeV

  22. Excitation Energy---4He+8He √ ? √ How to describe the non-resonant breakup process? ---A simple evaporation formula was used here

  23. Summary of Ex. States We agree well with Freer et al and Saito et al., supporting the cluster structure. 4He+8He 6He+6He An overal shift of about 1.5MeV for the 6He+6Heband ---The difference between Ethres(GTCM) and Ethres(exp) is 1.7MeV ---This shift may be attributed to the adopted interaction strength. GTCM calculation by M.Ito(PRL100(08)182502)

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