MOMENTUM INTERCHANGE BETWEEN CATHODE-SPOT PLASMA JETS AND BACKGROUND GASES AND VAPORS AND ITS IMPLICATIONS ON VACUUM-ARC ANODE-SPOT DEVELOPMENT

Expressions are developed for the momentum flux density in collimated and expanding cathode-spot plasma jets by multiplying the ion flux density by the momentum carried by individual ions. Cathode spots placed in a gas background produce a hemispherical metal-vapor plasma region whose radius may be predicted by equating the plasma-jet momentum flux density with the background gas pressure. In hot anode vacuum arcs and in anode-spot vacuum arcs a vapor plume from the anode expands into the cathodic plasma. Significant expansion occurs when the anodic vapor pressure becomes comparable to the cathodic momentum flux density. © 1990 IEEE