Abstract:
Background Electron cyclotron resonance heating (ECRH) is essential for plasma heating in magnetic confinement fusion, relying on high-power gyrotrons. Advanced fusion projects such as ITER, CFETR, and BEST require large numbers of high-frequency, high-power, long-pulse gyrotrons. Although such devices have been developed internationally, a fusion-compatible long-pulse megawatt gyrotron had not been achieved in China.
Purpose This letter presents recent experimental results from a 175 GHz long-pulse gyrotron developed at China Academy of Engineering Physics, aiming to validate its design and demonstrate 100 s continuous operation at the hundred-kilowatt level.
Methods The gyrotron uses a diamond window, operates in the TE28,11 mode, and employs a triode magnetron injection gun and a single-stage depressed collector with vertical sweeping. Power was measured calorimetrically using a water load, and thermal behavior of key components was monitored. Systematic conditioning and parameter tuning extended pulse length progressively.
Results The gyrotron achieved a stable output of 500 kW for 100 s with 46% total efficiency. Output frequency remained at 175.04 GHz with less than 40 MHz drift. The measured efficiency matches the design expectations, confirming stable device performance. This is China’s first hundred-kilowatt-level 100 s ECRH gyrotron operation.
Conclusions Successful 500 kW/100 s operation validates the gyrotron design and supports its application in domestic fusion devices. Future efforts will upgrade the power supply for megawatt long-pulse operation and conduct joint tests with domestic fusion facilities.
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