Dual frequency gyrotron development for JT-60SA

A new dual frequency (110 GHz and 138 GHz) gyrotron development began for JT-60SA. An output power and efficiency higher than 1 MW and 30% with a peak heat load lower than 1.4 kW/cm
²
were obtained for both frequencies in calculation. High mode conversion efficiencies of the quasi-optical mode converter (96.8% for 110GHz and 98.3% for 138GHz), which is higher than the previously developed 110 GHz long pulse gyrotron (96.5%), was obtained. The new gyrotron was fabricated and operation started from the middle of June 2012.