Performance of the microwave reflectometry diagnostic for density profile measurements on ASDEX Upgrade

The broadband reflectometry system on ASDEX Upgrade is now routinely provid ing electron density profiles with a minimum temporal spacing of 30 mus. Th e plasma is probed from zero density to n(e) = 6.64 x 10(19) m(-3) at the l ow field side with combined O and X modes, and from n(e) = 0.318 x 10(19) t o n(e) = 6.64 x 10(19) m(-3) at the high field side using O mode. Here we a nalyze the performance of the diagnostic for profile measurements taking in to account its design options and the experimental results obtained in a wi de range of plasma regimes. We address several questions, in particular the measuring range of the antennas and the range of density gradients. It is shown that it is possible to obtain a detailed evolution of the density pro file and density gradient even in the presence of turbulence, providing tha t sufficient data can be extracted from the plasma. The radial movements of the plasma can be measured with great accuracy, which is especially import ant for the use of reflectometry for plasma position control, as is propose d for the International Thermonuclear Experimental Reactor. The experimenta l results demonstrate that the frequency modulation of a continuous wave re flectometry system on ASDEX Upgrade can provide reliable and accurate densi ty profile measurements at both sides of the plasma with automatic analysis . (C) 2001 American Institute of Physics.