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A hollow cathode hydrogen ion sourceHigh current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. This paper describes a hydrogen ion source which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency. A 1.3-cm-diam hollow cathode using a low work function material dispenser performed satisfactorily over a discharge current range of 10-90 A. Cylindrical probe measurements taken without ion extraction indicate maximum ion number densities on the order of 10 trillion/cu cm. Discharge durations ranged from 30 sec to continuous operation. Tests with beam extraction at 2.5 keV and 30 A discharge current yield average ion beam current densities of 0.1 A/sq cm over a 5-cm extraction diameter. Results of this study can be used to supply the baseline information needed to scale hollow cathodes for operation at discharge currents of hundreds of amperes using distributed cathodes.
Document ID
19780055926
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Sovey, J. S.
(NASA Lewis Research Center Cleveland, OH, United States)
Mirtich, M. J.
(NASA Lewis Research Center Cleveland, Ohio, United States)
Date Acquired
August 9, 2013
Publication Date
January 1, 1977
Subject Category
Plasma Physics
Meeting Information
Meeting: Symposium on Engineering Problems of Fusion Research
Location: Knoxville, TN
Start Date: October 25, 1977
End Date: October 28, 1977
Accession Number
78A39835
Distribution Limits
Public
Copyright
Other

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