Gyrotron Microwave Heating of Vacuum Arc Plasma for High-Charge-State Metal Ion Beam Generation

High-charge-state heavy metal ion beams have been formed by high-power microwave heating of vacuum arc plasma confined in magnetic traps. Two types of magnetic traps were investigated: one is a simple mirror configuration, and the other is a cusp configuration with inherent “minimum- $B$ ” structure. Pulsed high-power ( $>$ 100 kW) gyrotrons with frequencies of 37.5 and 75 GHz were used for heating the vacuum arc plasma injected into the traps. Two different approaches were used for injecting the metal plasma—axial injection from a miniature arc source located on axis near the microwave window and radial injection from sources mounted radially at the midplane of the trap. High-charge-state heavy metal ion beams were extracted from the heated plasma.