Analysis of single pass ECH propagation and absorption experiments in MTX

Summary form only given. An experiment is being designed to measure the single-pass propagation and absorption of electron cyclotron heating (ECH) waves in dense plasmas and to compare the results with theoretical predictions. Calculations of microwave transmission through the MTX (Microwave Tokamak Experiment) 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. Ray-tracing calculations show substantial refractive spreading of the beam in the poloidal direction at densities above 1.5×10²⁰ m^-3, well within the range of the experiments. Future experiments with the free-electron laser (FEL) will also explore the nonlinear absorption of high-power ECH pulses. Calculations of the nonlinear absorption, including the spread in N_|| across the beam, have been done using approximate analytic absorption coefficients and with an orbit code. The calculations are compared with data from refraction/diffraction experiments using a high toroidal field, B₀=6.5 T, so that the cyclotron resonance is outside the plasma, and with absorption experiments at B₀ =5.0 T, using a range of plasma densities. Detailed analysis of the density and temperature profiles from the FIR interferometer and ECE data, respectively, for several of these FEL shots was used to calculate the transmitted power fraction reaching a small microwave horn on the inside wall of the tokamak