A Concept of Negative Ion Flow Velocity Measurement Using a Laser Photodetachment Velocimetry (LPDV)

Abstract

Abstract A concept of the thermal and flow velocities measurement for negative ions by means of a laser photodetachment technique, laser photodetachment velocimetry (LPDV), is presented. The difference in the temporal evolution of the photodetached excess electron current between the upstream and the downstream regions corresponds to the flow velocity, while the average of the recovery times corresponds to the thermal velocity, namely the negative ion temperature. Initial results in a divertor/edge plasma simulator MAP(material and plasma)‐II suggest that the parallel flow velocity is small in the periphery of the linear plasma column where the negative ions exist. The negative ion temperature is similar to that of helium ion obtained for helium discharges. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)