针对现有的放射性物质探测手段有效距离近和效率较低等局限性，考虑到高功率微波（HPM）良好的空间辐射特性，研究放射性物质对微波大气击穿特性的影响，以实现利用HPM远距离探测放射性物质的设想。阐释了微波脉冲等离子体击穿原理和自由电子对击穿特性影响，分析了放射性物质¹³⁷Cs射线产生自由电子的过程，在此基础上分析了HPM大气击穿时间和击穿阈值。基于HPM大气击穿等离子体实验装置，分别在6000 Pa、7000 Pa和8000 Pa的低气压环境对有、无放射源存在情形开展多次HPM辐照实验。实验结果表明：放射源的存在降低了约10%的HPM大气击穿阈值，缩短约50%的击穿时间。

In view of the limitations such as close effective distance and low efficiency of the existing radioactive source detection methods, high-power microwave (HPM) is used to detect radioactive materials over a long distance because of its good spatial radiation characteristics. In this paper, the principle of microwave pulsed plasma breakdown and the influence of free electrons on breakdown characteristics are explained, the process of free electrons generated by the decay of radioactive source ¹³⁷Cs is analyzed, and the HPM breakdown time and breakdown threshold are presented. Based on the HPM atmospheric breakdown plasma experimental apparatus, HPM irradiation experiments were performed multiple times in the low-pressure environment of 6000 Pa, 7000 Pa and 8000 Pa with presence and absence of radioactive sources. Experimental results show that the presence of a radioactive source lowers the HPM breakdown threshold by approximately 10% and can reduce the breakdown time by approximately 50%.