Investigation of the time-delay estimation method for turbulent velocity inference

A key challenge for the development of practical fusion power is to understand how particle and thermal transport are controlled by plasma turbulence. Of particular interest is the turbulent velocity field, which drives the "anomalous" fluxes. Current measurements of the velocity fluctuations have generally been limited to the outer edges of the plasma, but the recently proposed time-delay estimation method offers the possibility of measuring velocity fluctuations further into the plasma, motivating a comprehensive investigation of this method. The first step of this investigation, reported here, is to develop a greater degree of confidence in the method, by testing the technique on known signals and velocity fields. Issues such as optimal sampling rate, noise sensitivity, and the impact of signal processing techniques such as data windowing and interpolation are discussed. Future steps of the investigation will also be presented. (C) 2004 American Institute of Physics.