Deposition of a-C/B : D layers by ICRF-wall conditioning in TEXTOR-94

Wall conditioning and especially wall coating procedures like boronization or siliconization are indispensable for present day machines. They are also needed for future steady state plasma devices with superconducting coils a nd permanent magnetic fields like ITER. However, since important standard c onditioning techniques like Plasma Chemical Vapor Deposition (PCVD), based on de-glow discharges, are not compatible with those fields, new techniques have to be developed. This paper reports on first ion cyclotron range of f requency (ICRF)-assisted in situ deposition of a boron and carbon containin g layer of relevant thickness onto the first wall of a tokamak. The new met hod is called ion cyclotron coating (ICC) and is based on ICRF plasma produ ction in gas mixtures containing appropriate reactive precursor molecules, The new method is compatible with the magnetic held since it depends on its presence in order to produce a plasma. The geometrical arrangement of nece ssary facilities and their characteristic parameters for ICC in TEXTOR-94 w ill be described as well as the experimental procedure. The ICC-process its elf and the properties of the produced layer will be presented. (C) 1999 El sevier Science B.V. All rights reserved.