Abstract
Two megawatt-class gyrotrons at frequencies of 117.5 GHz and 170 GHz have recently been fabricated and tested at CPI. The 117.5 GHz gyrotron was designed to produce up to 1.8 MW for 10-second pulses, and will be used for electron cyclotron heating and current drive on the DIII-D tokamak at General Atomics. The 170 GHz gyrotron is specified as a 500 kW CW system, but has been designed with the goal of generating up to 1 MW CW. Oak Ridge National Laboratory will use the gyrotron in ITER ECH transmission line testing.
Highlights
Gyrotrons capable of generating 1-2 MW at mm-wave frequencies are a key technology for large-scale magnetically confined fusion experiments, which rely on localized electron cyclotron heating for plasma heating, current profile control, and suppression of potentially disruptive plasma instabilities
This gyrotron, which is to be used for transmission line component testing by the US ITER program, is specified as a 500 kW CW device, but is designed to produce 1 MW CW
2.2 Test results on 117.5 GHz gyrotron In Figure 2 we show a photograph of the 117.5 GHz gyrotron after installation into the test enclosure
Summary
Gyrotrons capable of generating 1-2 MW at mm-wave frequencies are a key technology for large-scale magnetically confined fusion experiments, which rely on localized electron cyclotron heating for plasma heating, current profile control, and suppression of potentially disruptive plasma instabilities. At a frequency of 117.5 GHz, a gyrotron designed to produce 1.5 to 1.8 MW of output power, for pulse lengths up to 10 seconds, has been fabricated and tested. At 170 GHz, CPI’s prototype gyrotron has been rebuilt to address deficiencies observed in initial tests. This gyrotron, which is to be used for transmission line component testing by the US ITER program, is specified as a 500 kW CW device, but is designed to produce 1 MW CW. The short-pulse (~5 ms) tests demonstrated output power levels up to 1.8 MW (for a beam current of 60 A, an accelerating voltage of 98 kV, and a collector depression voltage of 25 kV). Thermal imaging of the output beam confirmed the proper operation of the internal converter, consistent with cold-test measurements that were performed prior to completion of gyrotron assembly. Work is currently underway to improve the longpulse performance of the gyrotron
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