Generation of H sup minus ions in negative ion sources via recombination of H sub 2 sup + and H sub 3 sup + ions incident upon cesium and barium surfaces
Negative ion source development over the last decade has followed two general approaches: production of hydrogen negative ions by positive ion bombardment of low-work-function surfaces, notably cesium surfaces, and, the direct extraction of negative ions from a hydrogen discharge. The intensive development of this latter cesium-free volume-source system, however, has led to the useful generation of only rather modest current densities. Necessarily limiting the discharge hydrogen-gas-pressure to a value near ten millitorr so as not to impose excessive collisional beam losses in the accelerator column, production of negative ions in the volume source discharge is also limited. The useful H{sup {minus}} current densities achieved to date with these restricted gas pressures has been approximately 10mAcm{sup {minus}2}. But by properly shaping the electron-energy distribution function in both chambers of a tandem-source configuration, and be selecting axial lengths for these chambers in an optimum way, useful current densities in the range of 20--30Acm{sup {minus}2} should ultimately be achievable even with the constraint of a restricted pressure regime. The need for higher current densities at lower ion-source pressures has motivated the use of cesium or barium electrodes and/or convertors inside the source configuration. This paper discusses the use of these electrodes to generation H{sup {minus}} ions in negative ion sources.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- Sponsoring Organization:
- DOD
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6616972
- Report Number(s):
- UCRL-JC-104776; CONF-9005194--2; ON: DE90016476; CNN: AFOSR-ISSA-89-0039
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
430301* -- Particle Accelerators-- Ion Sources
ALKALI METALS
ALKALINE EARTH METALS
ANIONS
BARIUM
CATIONS
CESIUM
CHARGED PARTICLES
DESIGN
ELEMENTS
ENERGY
HYDROGEN IONS
HYDROGEN IONS 1 MINUS
HYDROGEN IONS 2 PLUS
HYDROGEN IONS 3 PLUS
ION SOURCES
IONS
KINETIC ENERGY
METALS
MOLECULAR IONS
PRODUCTION
RECOMBINATION
SURFACES
TRANSVERSE ENERGY