Effect of cesium seeding on hydrogen negative ion volume production

Journal Article · Thu Aug 20 04:00:00 EDT 1998 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.56360· OSTI ID:21199176

Bacal, M; Balghiti-Sube, F El; Elizarov, L I; Tontegode, A J ^[1]

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1. Laboratoire de Physique des Milieux Ionises, Laboratoire du C.N.R.S., Ecole Polytechnique 91128 Palaiseau (France)

The effect of cesium vapor partial pressure on the plasma parameters has been studied in the dc hybrid negative ion source ''CAMEMBERT III.'' The cesium vapor pressure was varied up to 10{sup -5} Torr and was determined by a surface ionization gauge in the absence of the discharge. The negative ion relative density measured by laser photodetachment in the center of the plasma extraction region increases by a factor of four when the plasma is seeded with cesium. However the plasma density and the electron temperature (determined using a cylindrical electrostatic probe) are reduced by the cesium seeding. As a result, the negative ion density goes up by a factor of two at the lowest hydrogen pressure studied. The velocity of the directed negative ion flow to the plasma electrode, determined from two-laser beam photodetachment experiments, appears to be affected by the cesium seeding. The variation of the extracted negative ion and electron currents versus the plasma electrode bias will also be reported for pure hydrogen and cesium seeded plasmas. The cesium seeding leads to a dramatic reduction of the electron component, which is consistent with the reduced electron density and temperature. The negative ion current is enhanced and a goes through a maximum at plasma electrode bias lower than 1 V. These observations lead to the conclusion that the enhancement of pure volume production occurs in this type of plasma. Possible mechanisms for this type of volume process will be discussed.

• OSTI ID: 21199176
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 439; ISSN 0094-243X; ISSN APCPCS
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CESIUM
ELECTRODES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRONS
ELECTROSTATIC PROBES
HYDROGEN
HYDROGEN IONS
ION DENSITY
ION SOURCES
LASER RADIATION
PARTIAL PRESSURE
PLASMA
PLASMA DENSITY
PLASMA DIAGNOSTICS
SURFACE IONIZATION
VAPOR PRESSURE