Investigation of W-fuzz cathode vacuum arcs operation time

Abstract

An experimental technique was developed to determine the vacuum arc operation time in the microsecond range on tungsten cathodes with a nanostructured fuzz layer. The samples used were tungsten plates exposed to helium plasma for 4 hours. As a result of exposure tungsten surface with helium ions, nanostructures called fuzz appear. They are thin tungsten filaments with a thickness of 10–50 nm. The average thickness of the W fuzz layer was 1 µm. A power source with a voltage of 200 V and a direct current of 0.1 to 0.7 A was used as arc supply. It is shown that, as for ordinary metal cathodes, the statistical integral distribution of the arc burning time for cathodes with a fuzz layer is random, has an exponential dependence. Vacuum arc operation time with W fuzz layer is an order of magnitude longer than for ordinary tungsten. Based on the experimental results, the average arc operation time was determined: ~1 μs for a current of 0.17 A and ~40 μs for a current of 0.7 A.