Pulsed dye laser diagnostics of vacuum arc cathode spots

• Published in: IEEE transactions on plasma science Vol. 20; no. 4; pp. 466 - 472
• Main Authors: Anders, A., Anders, S., Juttner, B., Botticher, W., Luck, H., Schroder, G.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.08.1992; Institute of Electrical and Electronics Engineers
• Subjects: Cathodes; Copper; Electric discharges; Electrodes; Electromagnetic wave absorption; Exact sciences and technology; Ignition; Optical materials; Optical pulses; Photography; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Spatial resolution; Vacuum arcs; Dye laser; Absorption spectrometry; Electric arc; Vacuum; Pulsed laser; Cathode spot; Experimental study
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/27.256775

The ignition and arc phases of vacuum arcs were investigated using differential dye laser absorption photography with simultaneous high spatial (micrometer) and temporal (nanosecond) resolution. The discharge duration was 800 ns, the current 50-150 A, the electrode material copper, and the cathode-anode distance less than 50 mu m. A 0.4 ns laser pulse (tunable, gamma =480-530 nm) was used to obtain momentary absorption photographs of the cathode region. During ignition, an optically thick anode plasma expanded toward the cathode, decaying within 25 ns after bridging the electrode gap. In the arc phase, a fragmentary structure of the cathode spots was observed in situ for the first time. The microspots have a characteristic size of 5-10 mu m. They appear and disappear on a nanosecond time scale. The plasma density of the microspots was estimated to be greater than (3-6)*10/sup 26/ m/sup -3/.< >