Carbon removal from tile gap structures with oxygen glow discharges

The removal of redeposited layers from tile gap structures with ITER-like geometries was investigated with various low-temperature glow discharges in oxygen. The test structure consists of 19 mm deep gaps with widths ranging from 0.5 to 4 mm. Erosion rates inside the gaps are reduced compared with a directly exposed witness surface. Smallest erosion is found for the lowest particle energies. Erosion at the bottom of the gap increases linearly with the gap width. Erosion on the side walls drops nearly exponentially with increasing distance from the top. Side wall erosion dominates the total eroded amount for all cases investigated. The total eroded amount integrated over the whole inner gap surface is larger than the amount that would be eroded on a flat surface with an area identical to the gap opening.