Diagnostics of negative ions using probe and laser in plasmas (oxygen discharge)

Abstract

The present paper deals with diagnostics of negative ions in oxygen in a DC (hollow cathode) discharge and RF (parallel-plate capacitive) discharge where negative ions are rich and play important roles. For the negative ion diagnostics, the probe technique and the laser photodetachment technique are applied to measure the negative ion density, the density ratio of negative to positive ions, the negative ion temperature as well as the negative ion species. Experimental results obtained by using the above techniques are shown and discussed. The solution of a rate equation using atomic and molecular processes is compared with the experimental results. This helps to search an optimum condition for the production of negative ions for an ion source and plasma processing, etc.