一套反宇宙射线HPGeγ谱仪系统的建立

Establishment of Anti-cosmic Ray HPGe Gamma Spectrometer

放射性核素监测是全面禁止核试验条约(CTBT)国际监测系统(IMS)4种监测手段之一。针对放射性核素样品活度低的特点,研制了一套反宇宙射线HPGeγ谱仪系统。相对于原始的γ能谱,在15~2700 keV能量范围内,反符合方法使全谱积分本底降低为原始谱的1/8,提高了对放射性核素的监测灵敏度。使用该系统对气溶胶样品测量7 d,^(140)Ba的最小可探测活度为10 mBq,达到了全面禁止核试验条约对核素实验室核准认证的技术要求。这不仅在CTBT放射性核素核查工作中具有重要意义,在辐射环境监测中也具有重要的应用前景。

Radionuclide verification is one of the four monitoring technologies used in International Monitoring System of Comprehensive Nuclear-Test-Ban Treaty(CTBT).The activity of radionuclides concerned by CTBT generally performs at the low-level.An anti-cosmic rayγspectrometer system with a HPGe detector was developed by using a combination of active and passive shielding techniques in order to improve the detection sensitivity and reduce the affections of background.By adjusting the system with a delay time and testing anti-coincidence count loss correction,compared with the originalγspectrum,the integral background in the energy range of 15-2700 keV is reduced by a factor of 8.The detection sensitivity is greatly improved by using the anti-coincidence method.For ^(140)Ba,the minimum detectable activity(MDA)is 10 mBq by using the anti-cosmic rayγspectrometer for 7 d measurement,which meets the technical requirements for certification of nuclide laboratory under the CTBT.It is not only of great significance for CTBT radionuclide verification,but also important for radiation environment monitoring.