Progress in the development of a multistage depressed collector system for high power gyrotrons

The development of a highly efficient multistage depressed collector system for the recovery of the major part of the spent electron beam energy is the key to increase the gyrotron efficiency. For several years there has been a significant effort at Karlsruhe Institute of Technology (KIT) in order to design a reliable, robust and efficient multistage depressed collector system for high power gyrotrons. The progress and the recent results of these studies will be presented.