High power test of a temperature controlled diplexer for electron cyclotron current drive system

A diplexer to be used as a fast switching device of high power millimeter wave for an electron cyclotron current drive system has been developed. The operation frequency of the device is tunable by controlling the thermal expansion of the cavity using a precision chiller. The tunable range of the diplexer is about 225 MHz at the frequency band of 170 GHz. The temperature dependence of the resonant frequency shift in the ring resonator diplexer is −3.4 to −3.9 MHz/K, which agrees with the theoretical prediction. The switching operation is confirmed up to rf power of 260 kW, a pulse duration of 100 ms, and a frequency of 170 GHz.