Initial Properties of Steady State RF Plasma Source by Two Turn Flat Loop Antenna for DEMO Relevant Divertor Simulation Experiment

To study DEMO divertors, some linear devices have attempted to create DEMO-grade high-density steady-state divertor simulation plasma in a stronger magnetic field. Helicon plasma sources using a flat-type antenna, which are one of the methods of radio frequency (RF) plasma generation in magnetic field, are expected to achieve this. In this study, we developed a new RF plasma source with a two-turn flat-loop antenna with RF sources having a maximum output power of 30 kW in continuous waves. A two-turn flat-loop antenna is expected to have a large-diameter discharge, and its radial density profile can be controlled. In addition, a water-cooled, double-disc quartz window unit was installed for a high-density, high-power discharge. In the initial experiment, argon and hydrogen plasmas were generated, and the integrity of the new device up to 5 kW, was confirmed in a discharge experiment. The magnetic field conditions were changed in this experiment, and a mode change from capacitively coupled plasma (CCP) to inductively coupled plasma (ICP) during argon discharge was observed. Under the experimental conditions of this study, neither argon nor hydrogen produced helicon plasma. This study hereby, discusses the plasma characteristics and provides guidelines for future development. & COPY; 2023 The Japan Society of Plasma Science and Nuclear Fusion Research