11 Experiment June 2012 PKU Group + Lanzhou Group

名称： 12Be 激发态集团结构研究。 内容： calibration ； 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 11Be12Be 能量 37MeV/A31.8MeV/A 流强 (T1&T2) 8000~18000 pps2000~3000 pps 纯度 ~90%~70% 次级靶 4000um Pb 100mg/cm 2 C 靶 200um Pb 空靶

Beam time 11Be 靶 4000um Pb200um Pb 空靶 FileFile &file File & file File time12h48min34h53min8h48min Total56h30min 12Be 靶 4He,6He 能量点刻度 100mg/cm2 C 靶空靶 FileFile File & file File Time2h 9min92h45min23h Total118h 约 11 天 260 小时

50cm y z 初级束 : 18 O 8+ 70A MeV 200enA~320enA 初级靶 : 9 Be 次级束 : 11 MeV ， ~10 4 pps, 纯度 ~90%, 到靶上能量： 33A MeV 次级靶 : 4mm Pb, 200um Pb, 空靶 MuNCos 实验测试

1. 11 calibration Method established H.B. You et al.

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 MeV – 0 度望远镜挑选出 10 Be

与 10 Be 符合后的中子能谱

2. 12 Be Cluster structure in excited states Z.H. Yang et al.

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

Conflicting results for 12 Be* 6He+6He,CH2 4He+8He ， with P4He+8He ， with C GANIL Ref1 Freer MSU Ref2 Charity Ref1: PRL82(99)1383 Ref2: PRC76(2007)064313

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

MSU exp., R.J. Charity et al. (PRC-2) PRC76(07) Be, 50 MeV/u, 10 5 pps, C target 0.4 mm, CH target 1 mm. beam spot 1 cm x 2 cm 16 HERA telescopes: DSSD(1.5mm thick, 2mm strip) + CsI + 4 LASSA: ; DSSD(0.5 mm thick, 3mm strip) + CsI very much contradicting GANIL exp. (Freer et al) PRC78(08) the same exp. As above decay to 3 H, x Li etc. 12 Be + C, MSU exp.

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

Particle Identification 4He 6He 8He E ΔEΔE

Excitation Energy 4 He+ 4 He 4 He+ 6 He 6 He+ 6 He 4 He+ 8 He 2- x He events for 12 Be

12 Be-> 4 He+ 8 He E rel resolution(σ) Detection effeciency 12 Be-> 4 He+ 8 He

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

Excitation Energy--- 6 He+ 6 He Ex/MeV

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

GANIL (PRL82(99)1383) J420 Ex/MeV Intercept: 10.8MeV Slope: 0.15MeV

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

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