Measurements on the LANSCE upgrade H--source

For the upgrade of the Los Alamos Neutron Science Center (LANSCE) Facility, the Lawrence Berkeley National Laboratory is developing an H ^- ion generator that can deliver the required beam. The output current has to be 40 mA at a repetition rate of 120 Hz and a pulse length of 1 ms (12 % duty factor), and the normalized emittance must be less than 0.1 n mm mrad. During the last years, we improved the so-called surface-conversion source for the generation of higher H^- currents. Experiments with magnetic filter fields have shown that the output current increases linearly with the discharge power in contrast to saturation when operating without a filter. In the latest source configuration, the filter field is generated by the cusp magnets itself, resulting in a simple and reliable setup. In this paper we present measurements on the output current as a function of discharge power. We discuss operation conditions of the source at the required 40 mA output current. Furthermore, preliminary results using 2 MHz RF power with an antenna for plasma generation are described