Analysis of single pass ECH propagation and adsorption experiments in MTX

Initial ECH absorption experiments in the Microwave Tokamak Experiment (MTX) use single pulse, 140 GHz microwaves from an FEL with up to 1 - 2 GW peak power; experiments to date have been done in the range 0.2 - 0.4 GW. Future experiments will also use ECH power from a gyrotron and multiple pulses from the FEL. One of the goals of these experiments is to measure the single pass propagation and absorption of ECH waves in dense plasmas and to compare the results with theoretical predictions. Calculations of microwave transmission through the MTX access port, propagation of the waves through the plasma and the resulting power deposition profile on a calorimeter located on the tokamak inside wall have been performed. The microwave transmission calculations include the relative phase slippage of waveguide modes in the narrow tokamak port to determine the spatial structure of the wavefront at the duct exit. Ray-tracing calculations show substantial refractive spreading of the beam in the poloidal direction at densities above 1.5 x 1020 m-3, well within the range of the experiment