Extension of Frequency Tuning Band in sub-THz Gyrotrons with Strong External Reflections

We demonstrate that extension of frequency tuning bands in sub-THz gyrotrons can be provided by using strong external reflections. Simultaneously, it allows reducing the operating currents while maintaining the kilowatt output power level. Simulations show that using a Bragg-type reflector we can achieve 3 GHz smooth frequency tuning band in a 200 GHz gyrotron with output power up to 1 kW. Such parameters are needed for testing of quantum electrodynamics predictions through the spectroscopy of positronium.