High-purity ion beam production at high current densities with a liquid-helium-cooled series-field-coil extraction ion diode
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico (USA)
Experiments are described in which a high-purity, high-power (0.15 TW, 1 MeV) proton beam is generated from an ion source consisting of H{sub 2} gas frozen onto a liquid-helium-cooled copper anode at 4.2 K in a series-field-coil extraction diode on the 0.7 TW HydraMITE-II accelerator. Peak anode proton current densities of 2 kA/cm{sup 2} were measured. This current density is a factor of 100 higher than those obtained in previous liquid-helium-cooled cryogenic diode experiments on small accelerators and is in the range required for high-power ion beam applications. Thomson parabola, Faraday cup, and carbon activation measurements indicate an ion beam proton fraction close to 100% for the cryogenic source, compared to 50--70% for the standard hydrocarbon anode tested. The cryogenic proton source is believed to consist of no more than a few monolayers of molecular hydrogen. The hydrogen-coated cryogenic anode shows a faster initial anode turn-on than other materials. However, source-limited emission from the thin hydrogen layer results in a somewhat longer current risetime, reduced ion diode efficiency, lower proton current enhancement over the Child--Langmuir limit, and a proton spectrum of lower average energy than for the hydrocarbon anode. Techniques to overcome these limitations are discussed. Cryogenic ion sources consisting of frozen N{sub 2}, CH{sub 4}, and Ne have also been studied. In each case, high intensity beams consisting predominantly of components of the refrigerated gas were produced.
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5222033
- Journal Information:
- Journal of Applied Physics; (United States), Journal Name: Journal of Applied Physics; (United States) Vol. 70:6; ISSN 0021-8979; ISSN JAPIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATORS
ALLOYS
BEAM CURRENTS
BEAMS
COPPER ALLOYS
CURRENT DENSITY
CURRENTS
ELEMENTS
ENERGY RANGE
GIGAWATT POWER RANGE
HYDROGEN
ION SOURCES
KILO AMP BEAM CURRENTS
LINEAR ACCELERATORS
MEV RANGE
NONMETALS
NUCLEON BEAMS
PARTICLE BEAMS
POWER RANGE
POWER RANGE 100-1000 GW
PRODUCTION
PROTON BEAMS
SOLIDS
ULTRALOW TEMPERATURE