Experimental and analytical development of the application of a transit laser velocimeter

Spectron Development Laboratories, Inc. has designed, constructed and demonstrated a rugged, compact, and reliable coaxial backscatter laser transit anemometer system. Measurements have been made through a 1.25 inch thick window without seeding at a range of 400 mm from very clean air at 1200 m/s with 80 mW of laser power incident on the sampling volume and a 100 mm diameter collection lens. The system employs many refined and/or new techniques which include specially prepared single fiber optic light guides, spatial filtering of flare light from the opposite spot, high gain photomultiplier tubes with preamplifiers, filter/discriminators which reject single photon events and estimate pulse center time, microcomputer control of optics and electronics, with on-line flow parameter estimation and graphics display.