Development of 170 GHz high power gyrotron and transmission line for ECH in JAERI

The high order mode escalation which reduces the heat load at the cavity of 170 GHz has succeeded without the adjacent mode competition. We performed 0.5 MW-0.75 sec and 0.175 MW-10 sec oscillation, but the output power was limited by the gyrotron window. For this solution, we have lately confirmed that the large size window disk of diamond manufactured by chemical vapor deposition (CVD) has the outstanding property; low loss tangent (tanδ⩽1.4×10^-4) and high thermal conductivity (1800 W m^-1 K^-1) and is available for 0.5 MW continuous wave (cw) transmission. On the basis of the result above, the modified 170 GHz 0.5 MW, long pulse gyrotron with the diamond window has been fabricated. We will also construct the 100 GHz range transmission line and the high power (1 MW level) and long pulse transmission experiment will be carried out