A Two Frequency 1.5 MW Gyrotron Experiment*

Megawatt gyrotrons are an important microwave source for electron cyclotron heating and current drive (ECH/ECCD) in fusion plasmas due to their ability to produce megawatts of power at millimeter wave frequencies. The MIT gyrotron operates nominally at 96 kV and 40 A with 3 $\mu $s pulses and has previously demonstrated 1.5 MW of output power with $>$ 50 {\%} efficiency at 110 GHz with a depressed collector. A new cavity has been designed for 1.5 MW operation at two distinct frequencies: 110 GHz in the TE$_{22,6 }$mode and 124.5 GHz in the TE$_{24,7 }$mode. A new internal mode converter (IMC) consisting of a dimpled wall launcher and four smooth curved mirrors has also been designed and was optimized for both modes. Simulations of the IMC indicate that $>$ 98 {\%} Gaussian beam content could be achieved for each mode. Cold test results for the components will be presented as well as the current status of the hot test experiment.