低本底内充气正比计数管测量<sup>37</sup>Ar活度

低本底内充气正比计数管测量³⁷Ar活度

摘要: ³⁷Ar是全面禁止核试验条约现场视察重要监测核素之一，高灵敏地探测³⁷Ar活度是地下核试验监测的关键环节。本文研究建立了低本底内充气正比计数管³⁷Ar活度测量装置，在铅屏蔽室上、下各装配1个塑料闪烁体探测器，主动屏蔽宇宙射线在计数管中产生的本底。相对于原始能谱，反宇宙射线能谱中³⁷Ar峰区本底计数率降至原来的7.3%，测量24 h，³⁷Ar的最小可探测活度达2.5 mBq。

Abstract: ³⁷Ar is one of the important radionuclides for on-site inspection compliance with Comprehensive Nuclear-Test-Ban Treaty. High sensitive detection of ³⁷Ar is a key step for underground nuclear test monitoring. A low background internal gas proportional counter system was established in Beijing Radionuclide Laboratory. The background of proportional counter caused by cosmic-ray was actively shielded by plastic scintillator detectors which were equipped on the top and the bottom of the lead shielding. The background count rate of ³⁷Ar peak region in anti-cosmic spectrum was reduced to 7.3% of which in the original spectrum. Within 24 h measurement, the minimum detectable activity of ³⁷Ar of 2.5 mBq was achieved.