探测器自身放射性本底

CsI crystalCsI Powder

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t eaea

脉冲形状甄别 PSD

Pulse Shape Discrimination

i

ii

A

tAt

图 5.2.3 一个实测甄别谱形，采用电荷比较法。 左图是甄别谱，此图计算出的优质因子 FOM＝2.21

Quenching factor (ionization yield energy)

thR

eeR

E

outputee

outputRR

Ee

RR E

E

L

L

L

L

沟道效应

DAMA/LIBRA NaI(Tl) Scintillator at Gran Sasso : total 0.82 ton-year dataObserve annual modulation in the 2-6 keV single-hit signal band, total 11 cycles, > 8Reject gamma by PSDNo modulations at higher energy & for multiple-hits

December30 km/s~ 232 km/s

60°

June30 km/s

NaI 晶体实验

2-6 keV

6-14 keV

2-6 keV

6-14 keV

Annual Modulation in single hit at 2-6 keVAnnual Modulation in single hit at 2-6 keV

No Modulation for multiple hits at 2-6 keV No Modulation for multiple hits at 2-6 keV

No Modulation for single hit above 6 keVNo Modulation for single hit above 6 keV

multiple-hits residual rate (green points) vs single-hit residual rate (red points)

Single-Hit Power Spectrum

Single Hit 2-6 keV Signal Region

DAMA/NaI (7 years) + DAMA/LIBRA (4 years)

Total exposure: 300555 kgday = 0.82 tonyr

表 4-1： 各种常用闪烁体的性能比较

材料 最强发光

波长(nm)

发光衰减

时间

折射

率

密度

(g/ cm3)

光产额

(光子/ MeV)

NaI (Tl ) 410 0. 23 s 1. 85 3. 67 42000

CsI (Tl ) 565 1. 0 s 1. 79 4. 51 55000

ZnS(Ag) 450 0. 2 s 2. 4 4. 09 8Li (Eu) ～480 1. 4 s 1. 95 4. 08

Li 玻璃 395. 9 75ns 1. 53 2. 5

BGO 480 0. 3 s 2. 15 7. 13 8900

BaF2 310 6 s /

0. 6ns

1. 56 4. 89 9900

CWO ～500 5 s 2. 3 7. 9 19700

蒽 447 30ns 1. 62 1. 25

芪 410 4. 5ns 1. 63 1. 16

液体闪烁体 420 2. 4～4ns 1. 52 0. 9

HP Ge detector / PC Ge detector

High efficiency

High resolution

Large mass

Pure material

Low noise/ Low threshold

?10-710-610-610-510-3h lifetime (s) h

?10-810-510-610-610-3e lifetime (s) e

70040010100440,000h mobility h(cm2/Vs)

110080001000110010040,000e mobility e(cm2/Vs)

0.140.090.190.08Fano factor

4.24.64.44.22.97e-h pair creation energy (eV)

1.61.431.571.502.130.74Band gap (eV)

13, 5131, 3348, 30, 5248, 5280, 5332Atomic number

AlSbGaAsCdZnTeCdTeHgI2Ge (77K)Material

?10-710-610-610-510-3h lifetime (s) h

?10-810-510-610-610-3e lifetime (s) e

70040010100440,000h mobility h(cm2/Vs)

110080001000110010040,000e mobility e(cm2/Vs)

0.140.090.190.08Fano factor

4.24.64.44.22.97e-h pair creation energy (eV)

1.61.431.571.502.130.74Band gap (eV)

13, 5131, 3348, 30, 5248, 5280, 5332Atomic number

AlSbGaAsCdZnTeCdTeHgI2Ge (77K)Material

Semiconductor detector materials

HPGe 的体积，质量最大 ( Kg)

HPGe 的能量分辨最好

三种 HPGe 探测器

planar Coaxial detector

Vb

p (n)

p+ (n+)

n+ (p+)S0

S1

p

PCGe detector

反冲电子或核的次级电子空穴的收集形成信号

- V Q

t

Charge induction

+

+

- V Q

t

+

+

+

+

+

+

Charge induction

- V Q

t

+

++++++++

+

Charge induction

Planar detector with perfect charge transport

- V Qind

t

+ -

+ -

+ -