Design studies of the collector sweeping system for the 2 MW 170 GHz coaxial gyrotron for ITER

The design of the collector for the 2 MW coaxial gyrotron has been verified taking into account the effect of eddy currents in the collector walls by using the ANSYS finite element code. As a result, it has been found that the eddy currents in the walls significantly influence the sweeping behaviour of the electron beam along the collector surface. An estimation according to the well known skin effect is therefore not sufficient. This modified field distribution results in a strong reduction of the sweeping range and thus in an unacceptable increase of the power loading on the collector wall.