Development of a 28-GHz/50-kW/30-s Gyrotron System for Fusion Application

A complete 28-GHz/50-kW gyrotron system was developed by the Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang, China, as a plasma heating source for the EXL50 fusion device, a compact spherical tokamak constructed by the ENN Group in 2019. The gyrotron employs a triode magnetron injection gun, a TE02-mode cylindrical cavity, a built-in quasi-optical mode converter, a single-stage depressed collector, and a single-disk boron nitride window. The gyrotron system features a match optical unit, a superconducting magnet, a calorimetric dummy load, a high-voltage power supply system, and other auxiliary components, was delivered to the EXL50 site. In the acceptance test, five successive shots of each power over 50 kW were generated for 30 s at 28 GHz. An average power of 51 kW, a maximum power of 55 kW, and 46% overall efficiency were obtained. The gyrotron system was assembled in the EXL50 and applied to a plasma discharge experiment. The gyrotron is the first practical domestic gyrotron produced for fusion applications in China. The design and test results of this instrument are presented in this article.