Wall conditioning by microwave generated plasmas in a toroidal magnetic field

The suitability of microwave generated plasmas for the purpose of wall coat ing in purr toroidal magnetic fields is investigated in a special test benc h. We report on the results of layer deposition using methane plasmas as a systematic case study for future boron or silicon deposition by other gases (B2H6, SiH4). The produced coatings can be characterized as polymer-like s oft a-C:D-films with a high DIG-ratio due to the low energy of particles hi tting the wall. Neutral hydrocarbon radicals could be identified to play th e major role for film deposition. On the other hand, strong re-erosion indu ced by deuterium ions is observed in regions with plasma-wall contact. The spatial homogeneity and the characteristics of produced coatings are presen ted and observations are correlated with measured plasma parameters. The us e of pulsed plasmas for wall conditioning is compared with steady-state dis charges, (C) 2001 Elsevier Science B.V. All rights reserved.