Development of a submillimeter wave gyrotron, Gyrotron FU VA, with a carefully designed cavity

A new submillimeter wave gyrotron, called Gyrotron FU VA, is now in an advanced stage of development which is being pursued in collaboration between the FIR Research Center at Fukui University, the Institute for Plasma Research at the University of Stuttgart and the Institute for High Power Pulse and Microwave Technology at the Research Center (FZK) in Karlsruhe. One of the main design goals of this device is to achieve a high purity mode output. For this reason, a carefully designed resonant cavity has been developed and installed. Another objective is to attain a long-term operation by the use of an 8T He-free superconducting magnet. Here we summarize some recent results obtained in the experiments with the Gyrotron FU VA