ECR-Driven Multicusp Volume H- Ion Source.

We studied the negative ion current extracted from the plasma created by seven elementary ECR sources, operating at 2.45 GHz, placed in the magnetic multipole chamber “Camembert III”. We varied the pressure from 1 to 4 mTorr, with a maximum power of 1 kW and studied the plasma created in this system by measuring the various plasma parameters, including the density and temperature of the negative hydrogen ions. We found that the electron temperature is optimal for negative hydrogen ion production at 9.5 cm from the ECR sources. The tantalum-covered wall surface pollution reduces the extracted negative ion current and enhances the electron current. Tantalum evaporation has a positive effect. The use of a grid and of a collar in front of the plasma electrode did not lead to any enhancement of the extracted negative ion current. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]