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Proceedings Paper

Negative ions from magnetically insulated diodes
Author(s): Robert M. Prohaska; Amnon Fisher; Norman Rostoker
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Paper Abstract

1407_63In testing a gas puff cathode, it was found that a hydrocarbon gas, butane, gave better results than hydrogen or ammonia. Butane's long molecule may provide both a larger collision cross section and probably some ability to absorb excess collision energy in internal vibration. The butane puff diode gave much lower current density than a solid polyethylene cathode and the difference might be attributed to the lower density of the butane puff versus the solid cathode. The emittance of the puff diode was much better with an angular spread of only a few milliradians. A new generation of puff valves have been developed which have demonstrated opening speeds faster than the existing valve by about a factor of two. Use of the new valve will let one determine if gas density really helps and if it does, the design of the valves can be further refined for about another factor of three improvement. UV irradiation of solid polyethylene cathodes is studied. A titanium hydride active cathode remains an option if it proves to be the best performer. Magnetic insulation much stronger than the 8 kG used to date may be necessary to obtain the best results. As a first step a cathode is being developed with internal insulation coils and an internal capacitor bank requiring no outside connection during a shot. Magnetic field lines in such a diode always close back on the cathode providing minimum leakage for a given field strength. External coils can be added to enhance the insulation if needed. Such a design will be relatively self-contained and so could be installed on beam generators in the USSR.

Paper Details

Date Published: 1 April 1991
PDF: 7 pages
Proc. SPIE 1407, Intense Microwave and Particle Beams II, (1 April 1991); doi: 10.1117/12.43533
Show Author Affiliations
Robert M. Prohaska, Univ. of California/Irvine (United States)
Amnon Fisher, Univ. of California/Irvine (Israel)
Norman Rostoker, Univ. of California/Irvine (United States)

Published in SPIE Proceedings Vol. 1407:
Intense Microwave and Particle Beams II
Howard E. Brandt, Editor(s)

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