Theoretical and experimental investigations of submillimeter CW gyrotrons in IAP RAS

The paper presents an overview of research activity for development of relatively low-power (10-100 W) submillimeter CW gyrotrons at the IAP RAS The design of CW IAP RAS gyrotrons on the second harmonic of gyrofrequency in the range 0.2-0.8 THz is discussed in this paper. The choosing of the operating mode was made basing on the one hand at the density of the parasitic mode spectrum, especially on the fundamental harmonic and on the other hand on possibility of formation of the electron beam in a magnetron injection gun. Optimization of the cavity profile for these gyrotrons was made and the maximum efficiency for reasonable accelerating voltage from 5 kV to 20 kV and current of the electron beam up to 1 A was determined. The main results of these calculations are presented in table 1. Also for these gyrotrons the influence of parasitic modes at the fundamental and second harmonics of the cyclotron frequency was investigated. One of these devices -0.26 THz gyrotron was developed, manufactured and tested at IAP RAS. The maximum CW output power of 200 W for accelerating voltage 16 kV and beam current 0.3 A was obtained at the experimental tests. During more than 8 hours CW operation tests at the customer´s site (BRMZ of Frankfurt University) the frequency and power stability of 5*10^-6 and 1 % respectively was demonstrated.