Design and Experiment of a 220/420-GHz Gyrotron for Nondestructive Evaluation

We report the design and experiment of a 220/420-GHz gyrotron oscillator for nondestructive evaluation which operates at the fundamental near 220 GHz and the second harmonic near 420 GHz of the electron cyclotron resonance frequency. Through optimizing electron gun for both operation modes, the TE
₂₆
mode at 423.1 GHz and the TE
₀₃
mode at 221 GHz are observed at output powers up to 8 and 6 kW, respectively, by only changing the beam voltage at a magnetic field of 8.2 T. The experimental results are in reasonable agreement with the design and simulation. In addition, the measurements of potential operation modes with peak output power are also presented in this paper.