Simulation of correlation reflectometry

Recently the principles of a new technique for diagnosing microturbulence called correlation reflectometry was presented. Two microwave beams with a small difference in frequency are launched against a density profile. By measuring the phases of the reflected signals, which are functions of cut-off layer positions, it is possible by crosscorrelation technique to get information of the relative motion of plasma perturbations between two different positions. We carry out a performance study of a model of a correlation reflectometer. A level of random plasma density fluctuations is modelled in plane geometry by superimposing moving density pulses on a given density profile. By the proper choice of the shapes of these pulses, we are in principle able to model any spectrum for disturbances propagating in the direction along the density gradient. With the speed of propagation known in the numerical experiment, we are able to determine the accuracy of the predictions of the characteristic velocity deduced from the crosscorrelation of the fluctuating phase signals of the reflectometer. Studies are carried out for statistically distributed disturbance velocities. The analysis uses a fullwave solution and results are compared with WKB-solutions. (author) 5 refs., 5 figs