Enhancement of pure volume negative ion production using a grid bias method or a magnetic filter method.

Volume production of hydrogen negative ion H(-) is studied in pure hydrogen plasmas using a grid bias method for plasma parameter control. The purposes of the present study are as follows. One is to investigate the possibility of controlling plasma parameters with a grid bias method in dc discharge plasmas; the other is to realize efficient negative ion production in H(2) plasmas and to discuss the difference in plasma parameters control and H(-) production between the grid bias method and the usual magnetic filter method. The relationship between plasma parameters and extracted H(-) ion currents is discussed. It is confirmed that both high and low electron temperature T(e) plasmas are produced in the separated regions when the grid is negatively biased. The negative ion production depends strongly on the grid potential and related plasma conditions. Within certain plasma conditions, H(-) production with grid bias method is much higher than one with magnetic filter method.