Design features and commissioning of pulse arc plasma source and power supply system for the VEST neutral beam injection system

Abstract

A short-pulse, high-power filament arc ion source is developed for the neutral beam injection (NBI) system of the Versatile Experiment Spherical Torus (VEST) device. The 0.6-MW NBI system is designed to deliver positive hydrogen ion beams at 20 keV for a pulse length >10 ms. In addition, the power supply system for the VEST NBI system is designed to change the beam injection energy during the pulse under VEST's initial target plasma parameters to increase beam–plasma coupling efficiency. To satisfy these requirements, a large-area, high-power arc plasma source with a pulse power system based on a Marx generator utilizing high-energy capacitors and a solid-state switching system is developed and successfully commissioned. In this paper, design features of the plasma source and the power supply system for the VEST NBI system is described and the arc plasma discharge characteristics are presented.