Terahertz-frequency-range large-orbit-gyrotrons for physical applications

We describe high-harmonic gyrotrons with axis-encircling electron beams developing on the basis of two experimental setups. The 30 keV / 0.7 A CW gyrotron is developed for the spectroscopy applications. Recently, selective operation at the second (0.267 THz) and at the third (0.394 THz) cyclotron harmonics were achieved. Special quasi-regular cavities are designed to to achieve the fourth-harmonic operation at frequencies of up to 0.65 THz. The pulsed 80-100 keV / 0.7-1.0 A gyrotron is aimed to provide high-power microwave pulses at the third cyclotron harmonic at frequencies close to 1 THz. Now we study possibilities to increase the peak level of the output power up to the level of several kW in order to use this gyrotron in plasma applications.