Surface Analytical Observations During Construction and Initial Operation of TCSU

Abstract

To minimize radiation-loss effects, preparation and in-situ conditioning of plasma-facing surfaces in the Translation Confinement and Sustainment Upgrade experiment (TSCU) was carried out with utmost attention. To assess the condition of the TCSU first walls during the construction and operation, chemical and morphological surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) were utilized. Here we present a summary of the preliminary and ongoing work performed for TCSU wall-conditioning, including preparation of UHV compatible surfaces, glow discharge cleaning (GDC), and siliconization. Effective techniques were developed for cleaning various plasma-facing components, including Al flux rings, stainless steel chambers and components, and quartz surfaces, prior to their installation. Helium-GDC was tested and proved to be useful in reducing the plasma impurities; however, extended periods of GDC resulted in the coating of quartz surfaces due to the sputtering of neighboring stainless steel walls by energetic glow particles. In addition, as a wall conditioning technique, siliconization has been examined in a separate system dedicated for detailed analysis of the process.