Optical profilometry on intense neutral beams

A scanning instrument to measure the optical profile of a high-power neutral beam is described. The instrument is capable of both spectral and spatial resolution of Doppler-shifted Balmer-alpha radiation from the beam. To interpret the line-integral data from the scanner a theoretical model giving both the three-dimensional beam particle density and expected (line-integral) optical profiles is presented. By fitting empirical light profiles to experimental data, it is shown how information on beam divergence, beam steering, uniformity and hydrogenic species ratios can be obtained. (author)