NEGATIVE-ION PRODUCTION IN LARGE-VOLUME SOURCE WITH SMALL DEPOSITION OF CESIUM

Experimental data on the enhancement of D- (H-) negative ion productio n due to cesium injection into a large volume multiampere negative ion source (MANTIS) are described. The directed deposition of small cesiu m amounts (5-100 mg) from a compact, movable oven, placed into the cen tral part of a MANTIS gas-discharge box was used, A calorimetrically m easured D- beam with an intensity up to 1.6 A and an extracted current density up to 4.2 mA/cm(2) (beam energy 25 kV) was obtained. Exactly 30 mg of cesium provides at least one month of source operation (1000 pulses with a discharge pulse duration of 4 s). The effect of cesium o n NI enhancement was immediately displayed after the distributed Cs de position, but it needed some ''conditioning'' of cesium by tens of dis charge pulses (or by several hours ''pause'') in the case of a localiz ed Cs deposition. No degradation of extraction-acceleration voltage ho lding on within the tested range of cesium injection was observed. (C) 1996 American Institllte of Physics.