Overview of the Microwave Tokamak Experiment operation and developments

The Microwave Tokamak Experiment (MTX) is being operated to demonstrate the feasibility of using intense microwave pulses (up to 6 GW peak power) from a free electron laser (FEL) to provide electron cyclotron heating for use in tokamaks, particularly high field machines. Initial results were obtained with the single pulse 140 GHz FEL at peak power levels of 200 to 400 MW late in 1989. Due to excessive transverse electron beam motion, and arcing in the accelerator cells, the accelerator was modified. These modifications have been successfully tested on a small portion of the rebuilt accelerator and have been incorporated in the remaining portion of the accelerator. A 140 GHz, 400 kW gyrotron was used to perform preliminary heating experiments during the fall of 1990. This same gyrotron system is serving as the master oscillator for the burst mode FEL. The new IMP steady state wiggler will be used to produce the high power microwaves for the burst mode. The FE construction has been completed, and it will be used for heating experiments scheduled for this fall