Status of the European 2 MW, 170 GHz Coaxial Cavity Gyrotron for ITER

A first industrial prototype of a 2 MW, CW, 170 GHz coaxial cavity gyrotron has been fabricated and will soon be delivered next. A suitable superconducting magnet is expected to be available in January 2007. Therefore experimental operation of the gyrotron experiments could start in February 2007. In parallel to the fabrication phase, extensive investigations have been performed on a short pulse 170 GHz coaxial gyrotron equipped with the same main components as the prototype tube. In general, the obtained results confirm the design calculations, although some discrepancies exist with respect to results of numerical simulations. In particular, the observed mode spectrum is more dense than predicted by calculations. This results in a reduced range of excitation of the nominal mode. Possible reasons for the observed discrepancy are under investigation. The performance of the quasi optical RF-output system is in agreement with the design, however, the Gaussian content of the RF output beam is unsatisfactorily low. The design of an improved RF-output system is in progress.