Beam intensity and brightness in H- and D- hybrid sources: Measurement of basic parameters

The photodetachment technique developed for measuring negative ion density and temperature has been used to study the difference between hydrogen and deuterium operation of the hybrid source. It was found that the negative ion temperature scales linearly with the electron temperature in both hydrogen and deuterium, but is higher in hydrogen than in deuterium for the same electron temperature. This dependence is affected by the volume of the source chamber. Recent progress in the photodetachment diagnostics of negative ions is reported. The presence of a capacitive component was observed in the photodetachment signal recorded using conventional, conductive probes. Capacitive probes have been constructed and tested. A bare probe at floating potential leads to workable signals. Experiments proving that the capacitive signal is proportional to the negative ion density are described