Preliminary Experimental Studies of the Proposed High Power RF Antenna to assist Glow Discharge Cleaning of SST-1 at Low Pressure

Abstract

The wall conditioning system for Steady-state Superconducting tokamak (SST-1) with a high power RF antenna to assist the glow discharge cleaning (GDC) is developed to operate at the low pressure. The antenna is designed as per the SST-1 port space constraints and simulated using CST-MWS. The simulated and measured results showed that the antenna is naturally resonating at ~184.1 MHz and 173 MHz with a return loss of ~12 dB and ~18 dB respectively. The antenna is then made to resonate at 13.56 MHz with an external L-type capacitive lumped element matching network. The fixed frequency (13.56 MHz) RF source is used to feed 2.5 kW of power to the antenna under the matched condition along with the 550 V DC voltage and current ~7.5 A is applied at the GDC electrodes. The initial test experiment achieved the dense plasma discharge of helium gas at ~1.3e-4 Torr which can help in achieving the wall conditioning of SST-1 with Helium gas at the low pressure up to ~1e-5 Torr in the next campaign of SST-1.