Simulation and measurement of frequency modulation in submillimeter-wave gyrotron

Frequency modulation of the gyrotron output has been numerically simulated employing the approximation of weakly relativistic, mono-velocity electron beam as well as a quasi-empirical approach, The simulation results are comp ared to a first experiment in the 300-GHz region performed with a submillim eter-wave gyrotron named "Gyrotron FU IV." The modulation amplitude of 30 M Hz has been achieved by a 120-V modulation of the accelerating voltage resu lting in the variation of the relativistic electron mass and in the corresp onding modulation of the electron cyclotron frequency. Calculated amplitude s of frequency modulation are in reasonable agreement with the experimental results.