OBSERVATION OF THE M = 1 MODE BY MICROWAVE TRANSMISSION MEASUREMENTS IN TORE SUPRA

Microwave transmission measurements in TORE SUPRA exhibit low frequency oscillations of the transmitted power, associated with a saturated m = 1, n = 1 mode, as observed by soft X-ray diagnostics. It is shown that these oscillations are related with refraction effects and specifically with modulations of the electron density profile due to a rotating magnetic island. An analytical solution of the ray equations modified by a rotating density perturbation is obtained which explains the frequency spectrum of the oscillations.