The Development of a 77-GHz, 1-MW ECRH System for the Large Helical Device

A 77-GHz, 1-MW gyrotron is being newly installed in the Large Helical Device not only to enhance the total heating power but also to increase the possibility of controlling the local plasma parameters. Our progress in installing the new gyrotron and evaluating its properties is discussed. We have already finished the installation of the peripheral components, including the transmission line, and conducted a test at 1 MW for a short pulse. Our plan is to operate this gyrotron at a power of up to 1 MW for 5 s. The conditioning of the gyrotron has been smoothly conducted, and a gyrotron output power up to 810 kW for 3.6 s has been achieved so far. The total injected power of electron cyclotron resonance heating to the plasma reached a value of [approximately]2.5 MW.