Experimental Investigation on a Relativistic Gyrotron Driven by a Carbon Fiber Array Cathode

The carbon fiber array (CFA) cathode has been successfully utilized in slow wave high power microwave (HPM) sources as a kind of explosive emission cathode (EEC), since it has good emission uniformity, a low explosive emission threshold, and a low cathode plasma expansion velocity. In this letter, the CFA cathode is being used for the first time in a coaxial cavity gyrotrons to increase the output power. The parasitic oscillations were successfully suppressed through the delicate design of the beam tunnel and the beam collector. In the experiment, the unwanted mode competition was suppressed, and stable microwave generation was realized. At an external magnetic field of 0.55 T, a diode voltage of 300 kV and a beam current of 500 A, the coaxial gyrotron generated the designed microwave at 10.3 GHz, with a pulse width was 40 ns and an output power of about 11 MW. The experimental power efficiency was lower than the simulation results, further efforts should be made to decrease the electron velocity spread.