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 and permanent magnetic fields like ITER. However, since important standard conditioning techniques like Plasma Chemical Vapor Deposition (PCVD), based on dc-glow discharges, are not compatible with those fields, new techniques have to be developed. This paper reports on first ion cyclotron range of frequency (ICRF)-assisted in situ deposition of a boron and carbon containing layer of relevant thickness onto the first wall of a tokamak. The new method is called ion cyclotron coating (ICC) and is based on ICRF plasma production in gas mixtures containing appropriate reactive precursor molecules. The new method is compatible with the magnetic field since it depends on its presence in order to produce a plasma. The geometrical arrangement of necessary facilities and their characteristic parameters for ICC in TEXTOR-94 will be described as well as the experimental procedure. The ICC-process itself and the properties of the produced layer will be presented.