Arcing in magnetic fusion devices

Referring to the similarities with arc discharges in the cathode material vapour in vacuum environment the characteristics of arcing phenomena in magnetic fusion devices are reviewed. Attention is paid to the cathode phenomena of vacuum arcs, such as the motion of arc spots, the arc tracks produced, the erosion rate and the charged and neutral components of the emitted cathode material. It is pointed out that arc tracks found in fusion devices do not always come from 'unipolar arcs', but they may also originate from different types of bipolar arcs. In present-day devices, arcing can be suppressed successfully by proper surface conditioning and smooth plasma operation. So far, however, there are no real means to theoretically predict the occurrence of arcing in fusion devices. (author). 136 refs, 8 figs, 3 tabs