Re-deposition of ITER-grade Be on plasma gun facility QSPA-Be: Characterization & plasma cleaning. (March 2022) - Dmitriev, A.M.
Highlights: · The paper presents studies of deposits produced by QSPA-Be machine. · Characterization of the deposits revealed PC-BeO stricture of the films. · The deposits were found to be similar to those obtained in JET-ILW outer divertor.· The one pulse of QSPA-Be provided deposition of ∼7 nm contaminant layer. · Test plasma cleaning of DTS protective window mock-ups is discussed. Abstract: Studies of contaminants obtained by spraying ITER-grade Be on a quasi-stationary plasma gun facility QSPA-Be are presented. Contaminating films, consisting mainly of Be and O in approximately equal proportions, were deposited on substrates of quartz, sapphire, single crystalline silicon (SC-Si) and NaCl crystal. Characterization of the deposits was performed using SEM, XPS, EBS, AFM, SE, TEM&SAED and micro-interferometry showing polycrystalline BeO films similar as found in JET-ILW. Films on SC-Si and NaCl were used to characterize their composition and morphology. The cleaning rates in the 81.36 MHz RF discharges in He or D2 at 2 Pa were measured on the SC-Si target. The measured etching rate of the deposited films was several times higher than the rate calculated from the theoretical value of beryllium oxide sputtering yield. Test cleaning of these contaminants was carried out in a capacitively coupled RF discharge (CCRF) from the surface of sapphire and quartz plates, which were considered as a mock-ups of the protective window of the first mirror unit (FMU) designed for ITER divertor Thomson scattering diagnostic system (DTS).