Radioisotopes of the noble gases xenon and argon can be important indicators of underground nuclear explosions. The Comprehensive Nuclear-Test-Ban Treaty (CTBT) includes monitoring capabilities to identify potential nuclear explosions conducted in violation of the CTBT. This monitoring currently focuses on measurement of the xenon isotopes ^131mXe, ¹³³Xe, ^133mXe, and ¹³⁵Xe. However, it is predicted that within 100 days of an underground nuclear explosion (UNE) ³⁷Ar would be released to the atmosphere at higher concentrations than xenon and with a higher signal to background ratio, depending on the radioxenon background levels. Therefore, inclusion of ³⁷Ar measurement capabilities at atmospheric International Monitoring System (IMS) stations may represent an improvement in the capability to detect a nuclear explosion.

At an IMS station location, an understanding of the expected range of background ³⁷Ar activity concentrations is critical to determining what levels would constitute an elevated concentration. This work describes our analysis of atmospheric samples for ³⁷Ar to evaluate the range of background concentrations. Samples were collected at multiple locations withing the United States, with approximately half coming from a sampler co-located with an IMS xenon monitoring station (RN75). The range of ³⁷Ar concentrations measured in atmospheric air samples was relatively narrow; for samples considered detectable, the minimum and maximum measured concentrations were 0.56 and 2.3 mBq/m³, respectively. Comparison of ³⁷Ar and ¹³³Xe concentrations measured at the IMS station indicated some correlation between the measured concentrations. The results presented here demonstrate the capability to detect background concentrations of ³⁷Ar in atmospheric air and provide a basis for potential implementation of ³⁷Ar monitoring at IMS stations.

稀有气体氙和氩的放射性同位素可能是地下核爆炸的重要指标。《全面禁止核试验条约》（CTBT）包括监测能力，以查明违反《全面禁试条约》进行的潜在核爆炸。该监视当前集中在氙同位素^131m Xe，¹³³ Xe，^133m Xe和¹³⁵ Xe的测量上。但是，据预测，在地下核爆炸（UNE）的100天之内，根据放射性氙的本底水平，会以比氙更高的浓度和更高的信噪比将³⁷ Ar释放到大气中。因此，列入³⁷大气国际监测系统（IMS）站的Ar测量能力可能代表了探测核爆炸能力的提高。

在IMS站位置，了解背景³⁷ Ar活度浓度的预期范围对于确定什么水平会构成升高的浓度至关重要。这项工作描述了我们对³⁷ Ar大气样品的分析，以评估背景浓度的范围。在美国附近的​​多个地方收集了样品，其中大约一半来自与IMS氙气监测站（RN75）并置的采样器。在大气样品中测得的³⁷ Ar浓度范围相对较窄。对于认为可检测的样品，最小和最大测量浓度分别为0.56和2.3 mBq / m ³。比较³⁷在IMS站测得的Ar和¹³³ Xe浓度表明测得的浓度之间存在一定的相关性。此处显示的结果证明了检测大气中³⁷ Ar的背景浓度的能力，并为在IMS站进行³⁷ Ar监测的潜在实施提供了基础。