McHale Laura E, Hecobian Arsineh, Yalin Azer P
Opt Express. 2016 Mar 7;24(5):5523-5535. doi: 10.1364/OE.24.005523.
The present work used a near-infrared methane cavity ring-down spectroscopy (CRDS) sensor to examine performance and limitations of open-path CRDS for atmospheric measurements. A simple purge-enclosure was developed to maintain high mirror reflectivity and allowed >100 hours of operation with mirror reflectivity above 0.99996. We characterized effects of aerosols on ring-down decay signals and found the dominant effect to be fluctuations by large super-micron particles. Simple software filtering approaches were developed to combat these fluctuations allowing noise-equivalent sensitivity of ~6x10 cmHJ Hz within a factor of ~3 of closed-path systems (based on stability of the absorption baseline). Sensor measurements were validated against known methane concentrations in a closed-path configuration, while open-path validation was performed by side-by-side comparison with a commercial closed-path system.
本研究使用近红外甲烷光腔衰荡光谱（CRDS）传感器来检测用于大气测量的开放路径CRDS的性能和局限性。开发了一种简单的吹扫罩，以保持高镜面反射率，并允许在镜面反射率高于0.99996的情况下运行超过100小时。我们表征了气溶胶对衰荡衰减信号的影响，发现主要影响是由大的超微米颗粒引起的波动。开发了简单的软件滤波方法来对抗这些波动，从而在封闭路径系统约3倍的范围内实现了约6×10⁻⁹ cm⁻¹ Hz的噪声等效灵敏度（基于吸收基线的稳定性）。在封闭路径配置下，根据已知的甲烷浓度对传感器测量进行了验证，而开放路径验证则通过与商用封闭路径系统并排比较来进行。
