Performance of a high vacuum, high temperature compatible millimeter-range viewing dump for the vertical ECE experiment on TCV

A high vacuum and high temperature compatible viewing dump, made of MACOR, was designed and installed in TCV for Vertical ECE experiments in the 75–110 GHz frequency range. Measurements of the dump prior to installation in the tokamak showed in more than 99% of absorption of the incoming radiation. The dump has remained in-vessel more than 7 years, protected from direct plasma exposure by carbon tiles. However it has still been exposed to carbon and boron deposition. Very recently, ex-vessel and in-vessel measurements were carried out over an extended frequency range up to 170 GHz to assess the change in performance of the dump due to exposure in the Tokamak. The new results show that the dump performance has not been adversely affected by seven years of in-vessel exposure and in fact match the original measurements, showing that the dump is still suitable for Vertical ECE experiments on TCV.