Role of cesium-ion bombardment in the formation of negative hydrogen ions on a converter surface

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.338320· OSTI ID:6639657

van Os, C F.A.; Granneman, E H.A.; van Amersfoort, P W

A fundamental study of the formation of negative hydrogen ions via surface conversion is presented. Employed is a novel type of converter, namely a porous tungsten button with liquid cesium flowing through it towards the side which is in contact with the plasma. A high cesium coverage, i.e., a small work function, can easily be maintained with this approach. This is related to the high flux of neutral cesium atoms to which the converter is exposed and to the small cesium density in the discharge. Despite the small work function, we obtain negative-ion yields which are an order of magnitude smaller than is usually found in more conventional experiments, in which the converter is cesiated via injection of cesium vapor into the discharge. Furthermore, our energy distributions show that no negative ions are formed via desorption by cesium-ion impact. This gives a strong indication that the extracted negative hydrogen ions are primarily formed via this process in cesium seeded discharges. Our view is confirmed by the observation that the negative-ion yield increases with an order of magnitude when a small amount of argon gas is injected into the discharge.

• Research Organization: Association EURATOM-FOM, FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands
• OSTI ID: 6639657
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 61:11; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

640302* -- Atomic
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ANIONS
BEAM PRODUCTION
BEAM-PLASMA SYSTEMS
BEAMS
CESIUM IONS
CHARGED PARTICLES
COLLISIONS
ELEMENTS
HYDROGEN
HYDROGEN 1 MINUS BEAMS
HYDROGEN IONS
HYDROGEN IONS 1 MINUS
ION BEAMS
ION COLLISIONS
IONS
METALS
MOLYBDENUM
NONMETALS
SPUTTERING
TRANSITION ELEMENTS