Field shaping to improve vacuum-diode voltage holdoff

Conference · Tue Jun 01 04:00:00 EDT 1982

OSTI ID:6729432

Furno, E J; Shafer, R E

In our work we need a small vacuum diode which will reliably hold off a pulse voltage in excess of 150 kV. These diodes typically have an interelectrode spacing of 6 to 10 mm with a glass insulator length 3 to 4 times the interelectrode spacing. We found that the overall holdoff voltage for a diode with a fixed insulator and interelectrode gap length was strongly affected by the position of the interelectrode gap. The highest voltage holdoff was obtained when the interelectrode space was at the negative end of the insulator. Experiments were made with two sizes of diodes, varying the location of the interelectrode space from the negative end to the positive end. The large diode high voltage holdoff ranged from 240 kV with the interelectrode space at the negative end to 180 kV with the interelectrode space in the middle of the insulator. The smaller diode high voltage holdoff ranged from a high of 200 kV with the interelectrode space at the negative end to 130 kV with the interelectrode space at the positive end. The minimum at the middle was not as pronounced in this diode. Since most of the high voltage breakdowns were across the glass insulator, electron avalanching was suspected. Computer generated field plots confirmed this possibility. With the interelectrode space at the negative end, the field lines direct any field emission electrons from the triple junction or the edge of the negative electrode away from the glass. All other configurations direct the electrons toward the glass. Thus shaping the field so that any field emission electrons are directed away from the insulator improves the high voltage holdoff by minimizing the probability of an avalanche type surface breakdown.

• Research Organization: General Electric Co., St. Petersburg, FL (USA). Neutron Devices Dept.
• DOE Contract Number: AC04-76DP00656
• OSTI ID: 6729432
• Report Number(s): GEPP-OP-667a; CONF-821024-6; ON: DE83002617
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420800* -- Engineering-- Electronic Circuits & Devices-- (-1989)
BREAKDOWN
DESIGN
DIODE TUBES
ELECTRIC DISCHARGES
ELECTRIC POTENTIAL
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRODES
ELECTRON TUBES
EMISSION
EQUIPMENT
FABRICATION
FIELD EMISSION
GLASS
PERFORMANCE TESTING
SIZE
TESTING
TOWNSEND DISCHARGE