TIME-RESOLVED OBSERVATION OF THE EROSION OF BORON-CONTAINING PROTECTIVE COATINGS ON WALL ELEMENTS OF TEXTOR-94 BY MEANS OF COLORIMETRY

The paper describes the investigation of the progressive erosion of an a-B:D coated test piece during 22 pulses in the SOL of TEXTOR-94. Tim e resolved observations by colorimetry reveal that the erosion proceed s in steps: during an intermediate phase the rates do not exceed appro ximate to -1.5 nm/s. Thereafter they jump to about -6 nm/s. This is du e to carbon ed when the concentration approaches approximate to 40%. T he changing composition may influence the ratio of the BII/CII emissio n near the surface. The process ends with a carbon rich layer on the r emnants of the boron film. Combination of different investigations (AE S, NRA, EPMA) results in a preliminary model description.