Design and experimental progress of a 105/140 GHz dual-frequency MW-level gyrotron

The design and latest experimental progress of a 105/140 GHz dual-frequency megawatt-level gyrotron for fusion applications are presented. The resonant cavity, quasi-optical mode converter and BN output window of the gyrotron adopt the design of dual-frequency sharing, the electron gun adopts the triode magnetron injection gun with dual-frequency multiplexing, and the collecting pole adopts the single-stage depressed collector. The experimental results are as follows: under the ms short-pulse condition with repetitive rate of 1 Hz, pulse powers of 710 kW at 105 GHz and 1.057 MW at 140 GHz have been achieved. The pulse width is 0.7 ms, and the total efficiency is 34% at 105 GHz and 49% at 140 GHz, respectively. Through pulse width extension and aging, the experimental results of 105 GHz/300 kW/2 s, 105 GHz/400 kW/1 s and 140 GHz/400 kW/1 s are obtained. The temperature of BN window reaches 606 ℃, 503 ℃ and 633 ℃, respectively, in the three states. The frequencies during long-pulse operations are stable, indicating that there are no parasitic modes. The experiment basically verifies the physical design of the device.