Effect of Ion Irradiation on the Surface Electrical Conductivity of Cucrzr at High Frequencies

The ohmic losses in the Electron Cyclotron Heating system of the DEMO nuclear fusion reactor depend on the surface electrical conductivity of the material at the frequency of the mm-wave beams generated in the gyrotrons. To reduce the ohmic losses, many components will be made or coated with materials with high electrical conductivity, such as CuCrZr. In addition, in the Equatorial Port Plug these components will also have to withstand very high irradiation doses. The objective of this work was to study the effect of ion irradiation on the surface electrical conductivity of CuCrZr at frequencies between 140 and 170 GHz. The samples were irradiated with Cu ions at 1, 3 and 10 dpa, which did not entail any change in the surface roughness, and were measured using a Fabry-Perot resonator. In addition, SEM-EDX analysis was performed to chemically characterize the surface of the samples. The results show that the surface electrical conductivity is reduced by more than 40 % at 10 dpa, which would translate in a significant increase of the ohmic losses, rising the cooling needs of the components in the Electron Cyclotron Heating system.