用反符合和热中子屏蔽降低γ谱仪本底

Experimental study on background reduction of γ-ray spectrometer using anticoincidence and thermal neutron shielding methods

新建的一台反宇宙射线低本底HPGeγ谱仪,在物质屏蔽的基础上采用反符合和热中子屏蔽联合方法,实验研究次级宇宙射线μ子和中子产生的本底。结果表明,反符合屏蔽(塑料闪烁探测器)能大幅度降低μ子产生的本底,还能有效抑制快中子与锗晶体和屏蔽材料非弹性散射引起的本底,100-2000keV能区反符合积分本底抑制系数可达8倍。热中子屏蔽(镉吸收片)的加入可明显降低锗晶体和屏蔽材料热中子俘获产生的本底,使511keV正电子湮灭峰本底的抑制系数由5.8倍提高到20.7倍,100-2000keV反符合积分本底抑制系提高到13.2倍。

Based on material shielding, a newly developed anti-cosmic low-background γ-ray spectrometer is used to conduct experimental study on background reduction of secondary cosmic muons and neutrons by combining anticoincidence shielding with thermal neutron shielding. The results show that the anticoincidence shielding （plastic scintillation detector） can reduce the μ background significantly on the HPGe detector, while effectively suppressing the background from the fast neutron inelastic scattering on the Ge crystal and shielding materials. The suppression factor of the anticoincidence integrated background is up to 8 in the energy region of 100-2000 keV. The addition of thermal neutron shielding （Cd absorber） can obviously reduce the background generated by the thermal neutron captured in the Ge and shielding materials, increasing the suppression factor of 511 keV γ-ray annihilation peak background from 5.8 to 20.7, and the suppression factor of anticoincidence integrated background in 100-2000 keV to 13.2.