Diagnostics and Modeling of H (-) Ion Sources
Final rept. 1 Sep 1989-31 Dec 1991,
ECOLE POLYTECHNIQUE PALAISEAU (FRANCE) LAB DE PHYSIQUE DES MILIEUX IONISES
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The negative ion temperature has been measured in hydrogen and deuterium, using the laser photodetachment technique. The negative ion temperature is strongly dependent on the neutral gas pressure, the discharge current and the electron temperature. It was inferred that many-body processes fields, turbulence or collisions in fields cause an increase in the negative ion temperature and adversely affect extracted beam quality. The deuterium negative ion temperature is significantly lower, compared to that found in hydrogen. The modeling of surface effects has been initiated by varying the surfacevolume ratio in a pure volume negative ion source. It was found that the increase of this ratio was only effective for enhancing the negative ion density when the power density was high enough, so that the volume destruction processes should control the production of vibrationally excited molecules. The modeling of a volume source with some amount of surface negative ion production due to positive ion and atom impact has shown that increasing the surfacevolume ratio leads to a significant increase in negative ion density.
- Plasma Physics and Magnetohydrodynamics