Frequency step-tuning experiments of a second-harmonic gyrotron from 270 to 420-GHz

A second-harmonic frequency step-tuning gyrotron is under development. The oscillation frequencies are separated by approximately 15-GHz steps in a range from 270 to 420-GHz. The operation modes were selected to convert into Gaussian like radiations by one internal mode converter. A triode electron gun was designed in order to operate in a wide range of magnetic fields. The oscillation tests were initiated with a demountable-type axial output tube with no mode-converter. All modes were successfully excited with the designed frequencies.