The set of data processing techniques used on ASDEX Upgrade to automatically evaluate edge
density profile characteristics from broadband data, obtained with the frequency-modulated
continuous-wave reflectometer, has recently been upgraded to include (i) an adaptive algorithm that
automatically optimizes the length of the window used in the spectrogram analysis of broadband
signals and (ii) a new method to estimate the edge pedestal density based on the evolution of the
local derivative of the group delay curve, removing the need for user supplied parameters. These
tools are especially important in cases where the group delay of the reflected signals varies
significantly in a short probing frequency range, such as when the profile exhibits a density shoulder
at the edge. The application of these techniques in ASDEX Upgrade H-mode density limit
discharges, to automatically obtain the time evolution of the edge pedestal parameters, namely, its
density, position, and width, shows a clear improvement both on the time-frequency resolution of
the group delay characteristic and on the detection of the density shoulder. |