2017 Volume 12 Pages 1206013
A 300 GHz pulse gyrotron has been developed for use in collective Thomson scattering (CTS) diagnostics in the Large Helical Device (LHD). Single-mode oscillation power of more than 320 kW was produced. The radiation beam has a Gaussian pattern. The frequency spectrum is very narrow and stable across the pulse width. No competing mode was observed in the oscillation pulse, including during the turn-on and turn-off phases.