Large current negative hydrogen ion beam production

Abstract

Large current negative hydrogen ions are extracted from a multicusp ion source with an extraction area of 25×44 cm2. By seeding a small amount of cesium vapor into a source chamber, the H− current is enhanced to several times larger than that in a pure hydrogen discharge, accompanied by a reduction of the electron current and the filling gas pressure. A H− current up to 16 A is obtained with a beam energy of 40 keV from 560 extraction holes of 9 mm in diameter each, where the current density is 45 mA/cm2. The H− current increases linearly with the input arc power.