11 be@ribll experiment june 2012
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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11Be@RIBLL ExperimentJune 2012
PKU Group + Lanzhou Group
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• 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
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Beams applied
• 18O8+ 70MeV/A 200enA~320enA• 初级靶: 9Be 4527um 降能片: 2759um Al
11Be 12Be
能量 37MeV/A 31.8MeV/A
流强 (T1&T2) 8000~18000 pps 2000~3000 pps
纯度 ~90% ~70%
次级靶 4000um Pb 100mg/cm2 C 靶200um Pb 空靶空靶
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Beam time
11Be
靶 4000um Pb 200um Pb 空靶File File 154-167&file 394-399 File 181-215 & file 227-233 File 216-225
time 12h48min 34h53min 8h48minTotal 56h30min
12Be
靶 4He,6He 能量点刻度 100mg/cm2 C 靶 空靶File File 338-348 File 235-309 & file 349-393 File 310-337
Time 2h 9min 92h45min 23hTotal 118h
约 11 天 260 小时
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50cm
y
z
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
MuNCos 实验测试
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1. 11Be@MuNCoS calibration
Method established
H.B. You et al.
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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
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与 10Be 符合后的中子能谱
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•
&
10
* * * * * *
*(1 )target acceptancecsi al livetime beam telescope
backgroundBe nMuNCoS N N
N
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2. 12Be Cluster structure inexcited states
Z.H. Yang et al.
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12Be:Generalized Two-Center Cluster model (GTCM) calculation
AO orbit
MO orbit
AO orbit
S↑ S↑
[PRL100(08)182502 ,PRC85(12)044308]
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Conflicting results for 12Be*
6He+6He,CH2 4He+8He , with P 4He+8He , with C
GANILRef1Freer
MSURef2Charity
Ref1: PRL82(99)1383 Ref2: PRC76(2007)064313
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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.
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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.
12Be + C, MSU exp.
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Detector Setup
Beam : 12Be , 31.8MeV/u , ~3000ppsTarget : Carbon, 100 mg/cm2
DSSD : 32 2mm-stip,300μm ,CsI : 2.5cm*2.5cm*3cm,
40cm13.5cm
5.8cm15.5cm18.8cm
PPAC1 DSSDTargetDSSD
SSD
CsI Array
PPAC2
32.3cm
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Particle Identification
4He 6He
8He
E
ΔE
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Excitation Energy
* 2
2 2 2 2 22( )( ) 2 ( 2 )( 2 ) cos
rel a b a b
a b a a b b a a a b b b
E M M M M M M
M M M T M T M T T M T T M
*MaM
bM
aT
bT
4He+4He 4He+6He 6He+6He 4He+8He
2-xHe events for 12Be
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12Be->4He+8He
Erel resolution(σ) Detection effeciency
12Be->4He+8He
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107.6KeV 8Be(g.s)
504.1KeV:9Be->8Be(2+)
Excitation Energy---4He+4He
Ref1:PLB580(04)129-14Be breakup
Ref1
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Excitation Energy---6He+6He
Ex/MeV 11.7 13.3
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◊4He(12Be,6He+6He)---- Saito et al,NPA738(04)337) -----angular distribution analysis
L=0 L=2
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GANIL exp@1999 (PRL82(99)1383)
J 4 2 0Ex/MeV 13.2 11.7 10.8
Intercept: 10.8MeVSlope: 0.15MeV
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Excitation Energy---4He+8He
Ex/MeV 10.2 12.0 13.4
How to describe the non-resonant breakup process? ---A simple evaporation formula was used here
?√
√
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Summary of Ex. States
GTCM calculation by M.Ito(PRL100(08)182502)
4He+8He 6He+6HeAn overal shift of about 1.5MeV for the 6He+6He band---The difference between Ethres(GTCM) and Ethres(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.