Electron emission from conductors subjected to intense, short-pulse electric fields
We studied electron emission from metal electrodes subjected to electric fields ranging from 0.5 to 2.5 MV/cm for pulse durations of 3 to 10 ns. We used two high-voltage pulsers for these tests; a 500- to 700-kV, 72-..cap omega.. pulser that generated a 3-ns gaussian pulse; and a 2-MV, 60-..cap omega.. pulser that generated a 10-ns flat-top pulse with a 1-ns risetime. The high voltage levels allowed emission studies using electrode spacings of several millimeters to several centimeters. Our studies emphasized bare and anodized aluminum surface shaving surface finishes that ranged from rolled stock to machined finishes of 2 to 400 ..mu..in. roughness. We also investigated polished stainless steel and brass. Emphasis was on first-shot performance with subsequent pulses applied to check for possible conditioning. The background pressure was typically 5 x 10/sup -5/ Torr. Our studies showed that for 10-ns pulse lengths, anodized aluminum surfaces could hold off more than twice the electric field strength of bare aluminum surfaces without appreciable electron emission. Anodized surfaces performed well at 1.0 to 1.5 MV/cm, while bare surfaces emitted at 0.5 to 0.7 MV/cm. For the shorter, 3-ns pulse lengths, anodizing was less effective at improving suppression of electron emission, while surface finish became the important factor. Electrodes with surface finishes of 40-..mu..in. or better roughness performed well at field strengths of up to 2.4 MV/cm. The behavior of velvet cloth as an emitter was also investigated using the 3-ns pulser. We found that velvet would emit within 3 ns at field strengths approaching 100 kV/cm. 9 refs., 9 figs.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA); Pulse Sciences, Inc., San Leandro, CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5482483
- Report Number(s):
- UCRL-96204; CONF-870656-49; ON: DE88005412
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
420200* -- Engineering-- Facilities
Equipment
& Techniques
ALLOYS
ALUMINIUM
BRASS
CHROMIUM ALLOYS
COPPER ALLOYS
COPPER BASE ALLOYS
CORROSION RESISTANT ALLOYS
ELECTRIC CONDUCTORS
ELECTRIC FIELDS
ELECTRODES
ELECTROMAGNETIC PULSES
ELECTROMAGNETIC RADIATION
ELECTRON EMISSION
ELEMENTS
EMISSION
INTERNAL ELECTROMAGNETIC PULSES
IRON ALLOYS
IRON BASE ALLOYS
METALS
PERFORMANCE
PULSES
RADIATIONS
STAINLESS STEELS
STEELS
SURFACES
WAVE FORMS
ZINC ALLOYS