High Stabilization of the Output Power of Submillimeter Wave Gyrotron

High frequency, medium power gyrotrons (Gyrotron FU series) have been developed at the Fukui University as radiation sources covering a broad frequency band from millimeter to submillimeter wave region. We have performed cw operation of the Gyrotron FU IV. However, due to the fluctuation of the cathode potential (~40 V), the output power and frequency were not stable (~5% and 2 MHz). The fluctuations were stabilized up to 1% and 300 kHz by decreasing the fluctuation of the cathode potential up to 3 V via introducing a smoothing circuit consisting of a resistor, an induction coil and capacitor