Design and operation of a 200 kW CW, 140 GHz gyrotron oscillator

This paper presents significant design issues and a description of the final tube design of a 200 kW CW, 140 GHz gyrotron, presently under development at Varian. Tests on our first two 140 GHz gyrotrons have produced output powers up to 100 kW CW, 150 kW for long pulses and 200 kW for short pulses. The first tube was rebuilt with an improved electron gun and has yielded higher efficiencies than our previous tubes. The 200 kW CW gyrotron design combines the best of the previous designs to provide high efficiency and high output powers at 140 GHz with good dynamic range and stability.