Test of SiC-electrodes in a high current pseudospark switch
- Univ. of Erlangen-Nuernberg, Erlangen (Germany). Dept. of Physics
The electrode erosion is a limiting factor in the lifetime of pseudospark switches. In a low pressure gas discharge like the pseudospark this leads to pre- and misfiring during a very long conditioning phase. Therefore alternative electrode materials were investigated. Polycrystalline SiC-discs embedded in plane molybdenum electrodes show promising results. The switch was triggered by a surface flashover in the back of the hollow cathode. At currents up to 100 kA corresponding to a holdoff voltage of about 20 kV tests were done by discharging a capacitor bank. The voltage breakdown and the current rise showed no difference to metal electrodes. Fast shutter photographs of the main gap showed the start of the discharge on axis, then a widening up to the edges of the central apertures. A very homogeneous plasma column of about 10 mm in diameter is burning stable in the center. A bright plasma sheath is observed on the SiC disc surfaces. No cathode spots (type A) were observed by this optical investigation: after the tests no erosion pattern of spots were detected. After current reversal the discharge reignited at the border SiC--metal in a few small sparks. These moved to the center and collapsed in less than 50 ns. Then the discharge burned again in a central plasma column. At the SiC surfaces a bright plasma sheath could be observed as before. First experiments with BC showed similar results. The time depending evolution of the discharge is presented.
- OSTI ID:
- 178230
- Report Number(s):
- CONF-950612--; ISBN 0-7803-2669-5
- Country of Publication:
- United States
- Language:
- English
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