Equivalent Model of Transient Gyrotron Cathode Response

The cathode power supply is one of the most important ancillary devices of gyrotrons. Some interesting transient phenomena about the cathode voltage and the cathode current were found in the gyrotron operation in the electron cyclotron (EC) resonance heating system of the Experimental Advanced Superconducting Tokamak. The cathode voltage drops to about 10% of the original value in about
$90~\mu \text{s}$
in the overcurrent case, which is much longer than the
$25~\mu \text{s}$
in the normal case. In order to explain these phenomena, an equivalent circuit model of the magnetron injection gun was proposed. The equivalent circuit is composed of parallel resistors and capacitors, and it can explain the test results very well. Using the equivalent circuit model to analyze gyrotrons can be an effective means of developing and operating an EC heating system.