Electron cyclotron wall conditioning with neon gas (Ne-ECWC) has been performed on the normal conducting spherial tokamak QUEST with metal walls under a trapped particle configuration with O-mode EC waves including X-mode polarization with a frequency of 8.2 GHz and an injection power of 16 kW. The Ne-ECWC removes hydrogen from the wall with small neon retention. The Ne-ECWC decreases hydrogen recycling at the following tokamak discharges, contributing to an improvement of the following tokamak plasma start-up: the plasma current increases and the start-up timing of the plasma current shifts forward. However, defects such as voids and bubbles are formed on tungsten surface exposed to the Ne-ECWC plasma.
This paper investigates the use of electron cyclotron wall conditioning with neon gas (Ne-ECWC) to remove hydrogen from the walls of a spherical tokamak, and its impact on plasma start-up. The Ne-ECWC was found to effectively remove hydrogen while causing minimal neon retention, leading to improved plasma current and start-up timing. However, the process also caused defects on the tungsten surface.