Infrared monitoring of gyrotron windows

A technique for monitoring the gyrotron output window surface temperature with an infrared camera while the gyrotron is in operation has been developed. The IR camera views the window through a perforated waveguide wall, and serves both as a guide for the safe operation at high average power of the tube, as well as an aid in the analysis of new window designs. Window temperatures were studied as a function of a number of parameters, including gun anode voltage, beam current, magnetic field, coolant flow, and load matching. The IR technique is applicable to many types of high average power microwave and millimeter wave tubes. Successful operation of the Varian 60 GHz gyrotron to 214 kW CW was guided by the infrared camera. Analyses on 28, 56 and 60 GHz gyrotrons have led to a number of design changes. A comparison with computer calculations is also presented.