Mechanism for negative-ion production in the surface-plasma negative-hydrogen-ion source
The system parameters and surface adsorption conditions of the surface-plasma negative-hydrogen-ion source are reviewed. A mechanism is developed for the production of negative ions by incident energetic hydrogen atoms backscattering from a cesiated tungsten surface. The active electronic level during the course of the collision is approximated as the sum of the negative electron affinity of the cesium hydride negative molecular ion and the image potential. The model predicts negative-ion formation for atomic collisions with all alkali-coated surfaces for alkalis from sodium through cesium. In the case of lithium, the model does not apply due to the breakdown of the image potential approximation close to the surface. Negative-ion formation is also expected to occur for incident positive ions which backscatter from the substrate tungsten as neutrals. The energy thresholds for incident atoms are established. (AIP)
- Research Organization:
- Lawrence Livermore Laboratory, University of California, Livermore, California 94550
- OSTI ID:
- 7268596
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 47:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
ION SOURCES
OPERATION
ADSORPTION
ALKALI METAL COMPOUNDS
ANIONS
ATOM-ATOM COLLISIONS
ATOMIC BEAMS
BACKSCATTERING
CESIUM
CESIUM HYDRIDES
ELECTRIC DISCHARGES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ELECTRON TRANSFER
HYDRIDES
HYDROGEN
IONIZATION
OPTIMIZATION
PLASMA
THRESHOLD ENERGY
TUNGSTEN
WORK FUNCTIONS
ALKALI METALS
ATOM COLLISIONS
BEAMS
CESIUM COMPOUNDS
CHARGED PARTICLES
COLLISIONS
CRYOGENIC FLUIDS
ELEMENTS
ENERGY
FLUIDS
HYDROGEN COMPOUNDS
IONS
METALS
NONMETALS
REFRACTORY METALS
SCATTERING
SORPTION
TRANSITION ELEMENTS
640301* - Atomic
Molecular & Chemical Physics- Beams & their Reactions