Recent improvements of the broadband FMCW reflectometry system for density profile measurements on ASDEX Upgrade

Abstract

The broadband FMCW reflectometry system on ASDEX Upgrade has had significant improvements extending its measuring capabilities both on high and low density plasmas: (i) the upgrade of the W band to probe electron densities up to 12.4× 1019 m-3 with O mode, (ii) Q and V frequency bands operating in X mode to probe the edge plasma and to provide information for O -mode profile initialization, and (iii) a new dynamic frequency calibration method to take into account all existing delays in the hyperabrupt varactor-tuned oscillator (HTO) tuning port and driver electronics. These improvements are particularly important to measure accurately the edge pedestal region of high density ITER relevant discharges. Density profiles obtained in high density discharges are presented and compared with results from both Li-beam and Thomson scattering diagnostics. © 2006 American Institute of Physics.