Wall material and wall temperature effects on negative ion production in a hydrogen plasma

Abstract

The effect of wall material and wall temperature on negative ion production in a hydrogen plasma has been studied. Under the same plasma conditions, within the combined uncertainties of the measurements, the same negative ion densities were found for Pyrex, stainless steel, copper and molybdenum. However, there seems to be a trend for stainless steel walls to produce somewhat higher negative ion densities. Contamination of the walls with hydrocarbons was found to reduce the negative ion density. It was also found that cooling the Pyrex walls leads to an increase in the negative ion density.