Ion Temperature and Neutral Density Measurements in the DC Octopole by Induced Optical Fluorescence.

A continuous wave tunable dye laser, operating either with a broadband (0.50 A bandwidth) or with a locked single frequency output (.0001 A bandwidth) was used to investigate the local density and velocity distribution of sodium metal neutrals present in a magnetically confined laser produced sodium metal plasma. In the broadband mode, the intensity of fluorescence radiation was proportional to the local neutral density, and from the temporal evolution of this quantity inferences concerning the efficiency of the limiter and the sticking probability of the sodium neutrals on the vacuum vessel may be evaluated. With the locked single frequency input the structure of the velocity distribution became accessible. In particular, when the plasma was seeded with additional sodium neutrals from an external oven source, the charge exchange products achieved sufficient concentration that the neutral doppler profile acquired recognizable wings.