Pulsed Absorption Diffractometer for Detecting Trace Species

随着大气污染的增加和公众对由此造成的环境破坏的新的、日益增强的认识，需要新的技术来测量大气中痕量物种的浓度。提取方法是在实验室中对密封的空气样本进行分析，这种方法价格昂贵，而且不适用于连续的、现场的浓度监测。科学研究实验室建议开发一种称为脉冲吸收衍射仪（PAD）的仪器来满足这一需求。该仪器的基础是检测瞬时体积衍射光栅，该光栅是在脉冲激光束被存在于照射区域的微量物质吸收后形成的。PAD将对万亿分之一的微量气体浓度敏感，比基于其他方法监测野外痕量物种的仪器好2-3个数量级。

With the increase in atmospheric pollution and a new, growing public awareness of resulting environmental damage, there is a need for new technology to measure the concentration of trace species in the atmosphere. Extractive methods, in which a sealed sample of air is analyzed in a laboratory, are expensive and are inapplicable to continuous, in situ monitoring of concentrations. Science Research Laboratory proposes the development of an instrument called a Pulsed Absorption Diffractometer (PAD) to fill this need. The basis of this instrument is the detection of a transient, volumetric diffraction grating that is formed after a pulsed laser beam is absorbed by trace species present in the illuminated region. The PAD will be sensitive to parts-per-trillion trace-gas concentrations, 2-3 orders of magnitude better than instruments based on other approaches to monitor trace species in the field.