Measuring Hydrogen Plumes With Raman Lidar

Prototype Raman lidar system measures concentration of hydrogen gas in atmosphere as function of position, with range resolution of 3 ft over 3,000 ft. Sensitive to concentrations smaller than 0.5 percent, 10 times below minimum flammable concentration. Pulsed ultraviolet laser beam excites Raman emissions from molecules to be detected. Backscattered light collected by telescope, filtered at appropriate wavelengths, and sent to photodetectors. Developed for use as safety monitor, and to study dispersion of hydrogen gas leaking into atmosphere.