Investigation of Tin Removal for Liquid Metal Tokamak Divertor by Low Pressure Argon Arc with Hot Tungsten Cathode System

The influence of a low-pressure argon arc with a hot tungsten cathode on the thin tin film with a negative bias voltage applied during the plasma treatment was investigated to study the tin film removal from the sample surface. Samples were prepared on a stainless-steel substrate using DC magnetron sputtering and hybrid HiPIMS assisted with electron cyclotron wave resonance (ECWR). During treatment an optical emission spectroscopy was employed to detect and characterize the emission line of tin spectrum and the electron density and temperature were measured by Langmuir probe. Morphological study by a scanning electron microscope helped to gain insight to the mechanism of tin removal from the substrate. In addition, elemental compositions of tin layer before and after treatment was measured by an energy dispersive X-ray spectroscopy. We believe that this study contributes to finding a proper treatment for tin removal from plasma facing surfaces of tokamaks using tin in the liquid metal divertor.