Raman Hydrogen Sensor, Phase 1

A fast-response 0.25 sec or faster gaseous hydrogen H2 sensor is required in process air ducting at AEDC to support the testing of engines for the National Aerospace Plane. A sensitivity of around 0.1 H2, over a sample pressure range of 2 to 15 PSIA is desired at humidity levels of up to 20 by weight. In the Phase I Raman Hydrogen Sensor Program, Spectral Sciences, Inc. SSI has built and tested a breadboard laser Raman scattering instrument for H2 concentration monitoring, and has demonstrated the feasibility of building a practical instrument that will meet the requirements of AEDC. All of the technical objectives were successfully accomplished. A detection limit of 0.0013 atm of H2 using 18 mW of optical power was demonstrated, and the fundamental response time was found to be 0.3 sec at 1 atm with the current, non-optimized flow system. In addition, the feasibility of active subtraction of background water signals was demonstrated, and a conceptual design for a Phase II brassboard instrument was also developed.