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Cathode degradation and erosion in high pressure arc dischargesThe various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.
Document ID
19850034294
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Hardy, T. L.
(NASA Lewis Research Center Cleveland, OH, United States)
Nakanishi, S.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1984
Subject Category
Spacecraft Propulsion And Power
Meeting Information
Meeting: International Electric Propulsion Conference
Location: Tokyo
Country: Japan
Start Date: May 28, 1984
End Date: May 31, 1984
Sponsors: Japan Society for Areonautical and Space Sciences, AIAA, and DGLR
Accession Number
85A16445
Distribution Limits
Public
Copyright
Other

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