Comparison of density fluctuation measurements between O -mode and X -mode reflectometry on Tore Supra

Reflectometry is a versatile diagnostic which allows both electronic density profile and density fluctuation measurements. Fast sweep heterodyne technique is particularly suitable for precise measurement of the phase of the reflected signal, which records the story of the wave propagation through the plasma up to the cutoff layer, including the density fluctuations. The present article exhibits a comparison of the density fluctuation radial profile measurements between fast sweep frequency technique, both using O -mode and X -mode polarizations, and fixed frequency technique. The correct agreement between all measurements of the relative values of the density fluctuation profiles reinforces the validity of the approximations used.