ELECTRODE PHENOMENA AND CURRENT DISTRIBUTION IN A RADIAL MULTICHANNELPSEUDOSPARK SWITCH

The microscopic structure and the spatial distribution of the cathode spots in a radial multichannel pseudospark switch have been investigat ed by means of scanning electron microscopy. Current pulses of about 1 5 mu s duration and peak amplitudes up to 340 kA have been applied. Wh en using stainless steel and copper as electrode material cathode spot s of type I and type II are observed. These cathode spots appear in gr oups (macrospots) with a diameter of several 100 mu m. Assuming that t he lifetime of the macrospots corresponds to the half period time of t he current pulse the distribution of the cathode spots within the macr ospots can be explained by a retrograde motion of the spots with a vel ocity of several 100 m/s in the self-magnetic field of the discharge c urrent. Furthermore, the spatial distribution of the cathode spots wit hin the macrospots can be interpreted by assuming a splitting and a re pulsion of the cathode spots. The electrode phenomena show that the di scharge current is distributed over a large area which is prerequisite for low erosion and long lifetime operation of the switch. (C) 1998 A merican Institute of Physics. [S0021-8979(98)02920-X].