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基于轻核衰变实验的考虑

华 辉北京大学物理学院

HIRFL-RIBLL1合作组会议 , 中科院近代物理研究所，兰州， 2012-7-5

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二、未来基于轻核衰变实验的考虑

一、已开展研究工作介绍

报告提纲

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一、已开展研究工作介绍

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detector

Beam on & Beam off mode

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Experimental detection system in PKU@2007

Neutron sphereNeutron sphere ：： 88 identical plastic scintillators identical plastic scintillators curved to a radius of curved to a radius of 100 cm100 cm.. E Each (157 cm in length, 40 cm in width at the center, andach (157 cm in length, 40 cm in width at the center, and 20 cm 20 cm in width at both ends, 2.5 cm in thickness)in width at both ends, 2.5 cm in thickness). The total solid angle . The total solid angle 3030%% of of 44..

Neutron wall: 20 short plastic scintillation bNeutron wall: 20 short plastic scintillation bars. Each (40.0 cm in length, 4.5 cm in widtars. Each (40.0 cm in length, 4.5 cm in width, and 2.5 cm in thickness).h, and 2.5 cm in thickness). The total solid aThe total solid angle ngle 8.88.8%% of of 44..

Implantation detector: NE102, 4.0 Implantation detector: NE102, 4.0 cm by 5.0 cm by 3.0 mm thick.cm by 5.0 cm by 3.0 mm thick.

44 clover high-purity germanium (HPGe) clover high-purity germanium (HPGe)

NIMA606, 645(2009)

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Our previous work with this device

? ?

Studied at NSCL

17C 18C

17N 18N 19N 20N 22N

23O

15B

16C

Studied at GANIL

11Li9Li

8He

Studied at many Labs

19C

17B

14Be

Studied at RIKEN

Studied at PKU

Phys. Rev. C 72, 064327(2005),Phys. Rev. C 75, 057302 (2007),Phys. Rev. C 80, 054315(2009).

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I sland of I nversion

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For 18N: an average beam purity of 95%.

For 21N: an average beam purity of 74.5%.

Disadvantage of Beam on & Beam off mode

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Nearly all the implanted nuclide and their daughters and granddaughters need to be considered in the decay calculations.

The background from the environment is very large!

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Disadvantage of Beam on & Beam off mode

A lot of radioactive nuclei wasted!

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Si PINDSSD Si PIN

Veto light particles

Continuous Beam mode

•Implantation DSSD: x-y position (pixel), time

•Decay DSSD: x-y position (pixel), time

Beta Counting System (BCS)

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e-

Si Strips

Continuous Beam mode

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Experimental detection system in PKU@2011

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PreampLog mode

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200 400 600 800 1000 12000

300

600

900

1200

1500

1800

Cou

nts

Energy (keV)

0 2 4 6 8 10 12 14 160

10

20

30

40

E (

keV

)

Strip number

front junction side rear ohmic side

207Bi源内转换电子能量谱 DSSD硅微条的能量分辨

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Beam ： 40Ar, 68.9MeV/u, ~60enARIB: 32Mg

LISE 计算

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粒子注入位置图

Pixel粒子最大注入率 0.053pps

190 200 400 600 8000

500

1000

1500

2000

2500

3000

3500

4000

0 200 400 600 8000

1000

2000

3000

4000ch

anne

l

E(MeV)

探测装置能量响应曲线

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Experimental results DSSD

No pixel limitation

pixel <4

Space correlation

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Primary experimental data DSSD

Same pixel

pixel <2

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0 500 1000 1500 2000 2500 30001

10

100

1000

10000

100000

Background

33Al

32Si

Cou

nts

/ 10m

s

Decay Time (ms)

33Si

T1/2=41.8± 0.1ms

0 500 1000 1500 2000 2500 30001

10

100

1000

10000

100000

Background

33Al

32Si

Cou

nts

/ 10m

s

Decay Time (ms)

33Si

T1/2=41.8± 0.1ms

NNDC T1/2=41.7±0.2ms A.C Morton et al PLB 544 274-279 (2002)

拟合得到的 33Al核衰变半衰期

2316 18 20 2230

40

Hal

f Tim

e [m

s]

Neutron number

100

200

300

400

20

40

60

20

40 Ne

Al

Mg

Na

NNDC PKU

实验得到的目标核衰变半衰期

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31Mgγ谱分析

511

597 947a

669a

a ： 31Al

b ： 31Si

1626a1612a

2314b1695b

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连续束研究的不稳定核位置

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二、未来基于轻核衰变实验的考虑1、提高探测效率

Si PINDSSD Si PIN

Veto light particles

DSSDDSSD DSSD

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2、优化整个探测设备布局

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3、基于 RIBLL束流强度的考虑

T1/2=92±10ms

Nuclide Counts CPS

33Mg 813 0.0016

Literature value T1/2=90.5±1.6msA.C Morton et al

PLB 544 274-279 (2002)

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Literature value T1/2=14.8±0.3msVandana Tripathi et al PRC 73, 054303 (2006)

T1/2=18.3±0.8ms

Nuclide Counts CPS

29Ne 87 0.0002

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未来研究目标

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Nuclide LISE++36Al 0.0084

35Mg 0.000334Mg 0.042233Mg 0.24533Na 0.000232Na 0.005531Na 0.068130Ne 0.000729Ne 0.003

Beam ： 40Ar, 68.9MeV/u, ~60enARIB: 34Mg

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Thank you!

Peking University