AbstractA TE22,6 gyrotron with conventional hollow cylindrical resonator has attained a maximum output power of 2.1 MW at 140 GHz and an efficiency of 34% (53% with depressed collector). Fast stepwise frequency-tunability with 1-s time steps has been demonstrated with this TE22,6 gyrotron at a power level of 1 MW. Fast frequency-tunable gyrotrons are of interest for controlling instabilities in magnetically confined plasmas. Two small auxiliary normal conducting magnets in the cryostat bore hole outside the cryostat have been added to the superconducting magnet system. A fast change of the magnetic field by ±326 mT results in a fast frequency change of about ±7.3 GHz with the center frequency at 140 GHz. A TE31,17 coaxial cavity gyrotron operated at 165 GHz has been developed. A maximum output power of 2.2 MW with an efficiency of 28% at a beam current of 84 A has been achieved with a pulse length of 1 ms. The maximum output efficiency of 30% (48% with depressed collector) has been measured at an output power of 1.5 MW at 56 A.