Introduction

From everyday life, we are familiar with discharges; consider atmospheric discharges which we observe in the form of lightning, and which equalize potential differences of some millions of volts within milliseconds. Very high temperatures can be generated with electric arcs, which were described for the first time by Humphry Davy in the year 1813. Two years later, they were applied to melt and fuse refractory metals [10]. The temperatures are 4700 K at the electrodes and up to 7000 K in the arc itself. With increased current densities, temperatures of up to 50000 K could be reached. These are the surface temperatures of blue-white glowing O-stars (our sun, a G-type, has a surface temperature of about 6000 K [11]).