Photoacoustic Sensor for High-sensitivity Measurement of Water Vapor

We propose to build a compact, rugged airborne laser photoacoustic spectrometric (LPAS) sensor based on a tunable mid-IR diode laser for continuous, real-time measurements of water vapor, and perform field tests to qualify it for dynamic airborne in situ monitoring of upper troposphere water vapor. An innovative diode laser frequency locking technique developed by us will be utilized for tunable diode laser wavelength stabilization. Our sensor will be based on our laboratory LPAS instrument (at technology readiness level TRL-4) that has already demonstrated successful detections of water vapor, chemicals, alcohols, and CWAs. It utilizes a tunable infrared laser (interband cascade or quantum cascade), a high sensitivity photoacoustic cell with an air sampler and an efficient algorithm to rapidly complete high sensitivity, selective multi-component measurements in under a minute. In Phase I we will carry out extensive laboratory tests of LPAS and a comprehensive analysis of the sensor performance to determine the limit of detection (LOD) and receiver operating characteristic (ROC) curves for the sensor and establish its feasibility. A rugged and portable prototype sensor (TRL-5) will be built in Phase II. It will be field tested in aircraft (TRL-6) and characterize the sensor.