NEGATIVE-ION DENSITY DETERMINATION USING PROBE TO DETECT PHOTO-DETACHED ELECTRON BY CONTINUOUS-WAVE LASER

Theoretical calculation of probe current increase caused by photo-deta chment of electrons by laser irradiation in a plasma and experimental studies have been done in order to determine the absolute negative ion density. The positive column of a hollow cathode DC Ar:O-2 discharge is used in the experiment. During laser irradiation of the anode, dete cted photo-detached electron current increases with increase of the la ser on-off frequency because of temporal space potential change. The O - densities determined from the theoretical calculation show good agre ement with those theoretically predicted based on Ichikawa's theory wh en the laser does not irradiate the anode.