H- production in pure hydrogen discharges of surface-plasma sources

2014 The pure-hydrogen discharges in surface-plasma sources with a semiplanotron electrode configuration are described. In short pulse (10-3 s) mode the extracted Hemission density was up to 1.1 A/cm2 at cathode discharge current density 60 A/cm2. The multi-slit short pulse extraction delivered the Houtput with current of up to 1 A. In the long pulse (0.6 s) mode the Hyield was 0.15 A at discharge current density 10 A/cm2. The experiments have shown strong dependencies of Hyield on the shape, temperature and conditions of cathode surface. The energy spectra of extracted Hions consisted of several groups, corresponding to the surface (anode and cathode) and volume origin of Hions. Revue Phys. Appl. 23 (1988) 1889-1892 DÉCEMBRE 1988, : Classification Physics Abstracts 29.25C 52.20 In the last decade the interest to Pure Hydrogen (PH) gas discharge systems for H-production has increased in connection with the study of a new intense channel for H-production via vibrationally excited molécules. This channel enabled one to explain the anomalously high negative ion density in hydrogen plasma [1] and high negative ion output from PH discharges [2]. The discovery of the surface-plasma negative ion production method [3], delivering the multiampere beams of Hwith an emission current density up to 5 A/cm2 gave a priority to the studies and development of Surface-Plasma Sources (SPS) with high current hydrogen glow discharge and cesiated electrodes. The Houtput from PH discharges of SPS had also relatively high emission density of up to 0.75 A/cm2 as it has been established [3] in 1972. Results on H-production in PH multi-aperture SPS with large emission surface are described below. The expérimental device. The PH discharges in SPS with a semiplanotron electrode configuration were investigated. The high current glow crossed field discharge was sustained in the extended narrow gap between the massive Mocathode and the anode cover (Fig. 1). Electron oscillations were maintained in the space between the cathode side projections along the magnetic field lines. One of the cathode ends was made with the increased up to 4 mm cathode side projections for improving electron confinement and accumulation and decreasing the hydrogen density in the glow discharge [4]. The discharge propagated over the Fig. 1. Layout of a flat cathode semiplanotron. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/rphysap:0198800230120188900