New experimental results on the gyro-TWT with a helically grooved waveguide

Experimental results are presented for a frequency-broadband efficient gyrotron traveling wave tube based on a novel microwave system in the form of a waveguide with a helical corrugation of its inner surface. The gyro-TWT utilizes a low-relativistic axis-encircling electron beam with an energy up to 80 keV, current up to 10 A and pulse duration up to 10 μs, which is produced by a thermionic cusp gun. The interaction between the beam and an operating mode of a helically grooved waveguide occurs at the second cyclotron harmonic. The maximum efficiency is measured to be 28%, the maximum output power amounts to 180 kW and the saturated gain is about 25 dB. At present the frequency bandwidth of 35.1-36.8 GHz (∼5%) is limited by capabilities of an available RF driving source.