使用短脉冲CO2激光器远程检测放射性材料
Remote detection of radioactive material using a short pulse CO2 laser
AI总结：
本研究利用70皮秒长波红外CO2激光脉冲，在10米远距离实现了基于雪崩击穿的3.6 mCi阿尔法粒子源远程检测，通过放大后向散射信号使灵敏度提高百倍以上，且该系统可扩展至100米以上。
摘要：
在大于辐射粒子范围的距离处检测放射性材料是国防和灾难响应等领域应用的重要目标。在此，我们展示了使用70皮秒长波红外（lambda=9.2微米）CO2激光脉冲，在10米的远距离上实现基于雪崩击穿的3.6 mCi阿尔法粒子源远程检测。这比我们之前使用中红外激光器的结果长约10倍。主要检测方法是从激光聚焦体积中产生的微等离子体的直接后向散射。后向散射信号在通过CO2激光链返回传播时被放大，灵敏度提高了100倍以上。我们还通过荧光成像表征了击穿等离子体，并提出了一个简单的模型来估计后向散射信号作为激光聚焦体积中种子密度剖面的函数。所有这些都是通过相对较长的驱动激光聚焦几何形状（f/200）实现的，该几何形状可轻松扩展到100米以上。
英文摘要：
Detection of radioactive material at distances greater than the radiated particle range is an important goal with applications in areas such as national defense and disaster response. Here we demonstrate avalanche-breakdown-based remote detection of a 3.6 mCi alpha-particle source at a stand-off distance of 10 m, using 70 ps, long wave infrared (lambda=9.2 micron) CO2 laser pulses. This is ~10X longer than our previous results using a mid-IR laser. The primary detection method is direct backscatter from microplasmas generated in the laser focal volume. The backscatter signal is amplified as it propagates back through the CO2 laser chain, enhancing sensitivity by >100X. We also characterize breakdown plasmas with fluorescence imaging, and present a simple model to estimate backscattered signal as a function of the seed density profile in the laser focal volume. All of this was achieved with a relatively long drive laser focal geometry (f/200) that is readily scalable to >100 m.
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