Modeling of H sup minus surface conversion sources; binary (H-Ba) and ternary (H-Cs/W) converter arrangements

Journal Article · Sun Sep 01 04:00:00 EDT 1991 · Journal of Applied Physics; (United States)

DOI:https://doi.org/10.1063/1.349365· OSTI ID:5251865

van Os, C F.A.; Kunkel, W B ^[1]; Leguijt, C; Los, J ^[2]

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1. Lawrence Berkeley Laboratory, University of California, 1 Cyclotron Road, Berkeley, California (USA)
2. Association EURATOM-FOM, FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, NL-1098 SJ Amsterdam (The Netherlands)

The production process for the formation of H{sup {minus}} ions in a surface conversion source is sputtering of hydrogen atoms from the converter surface layers by incident positive ions, followed by electron attachment via resonant charge exchange with the converter surface. The sputtering process is in direct relation to the converter surface composition. New experimental data led us to identify two different classes of converters: metallic converters, like solid barium(binary) and adlayer converters, like cesium on tungsten (ternary). For a binary converter the hydrogen in the surface layers is directly sputtered by the incoming ions. Consequently, the negative ion yield scales with the hydrogen concentration in the surface layers. In the cesium/tungsten system (ternary) the hydrogen at the surface is {ital believed} {ital to} {ital be} sandwiched between the cesium adlayer and the tungsten surface. Hence, the negative ion yield scales with the sputter coefficient of hydrogen on adsorbed cesium. This is experimentally confirmed.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5251865
• Journal Information: Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 70:5; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

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