Gyrotrons for ECH applications

Gyrotron oscillators have served as effective sources for electron cyclotron heating (ECH) applications in the area of magnetic confinement fusion. Successful development programs at frequencies at 28 GHz, 60 GHz, and 140 GHZ, have led to the availability of wide-range gyrotron sources with high-average-power capabilities. Since 1975, over 100 pulsed and CW gyrotrons with typical power levels of 200 kW at frequencies ranging from 28-106 GHz have been used by various fusion laboratories. Present development activity is aimed at providing sources that will generate power levels up to 1 MW CW at frequencies in the range 100-140 GHz for the ECH experiments that are currently being planned. Initial experimental efforts in this area have verified many of the concepts to be employed in forthcoming 1-MW CW test vehicles. Source requirements, that are even more formidable, are foreseen for the next generation magnetic fusion facilities. Frequencies ranging from 200-300 GHz with power generation capabilities of 1-2 MW CW per tube are being considered for these future applications. To this end, various gyrotron designs have been conceived that address these demanding specifications.