Autocorrelation analysis and statistical consideration for the determination of velocity fluctuations in fusion plasmas

A new statistical method is proposed and investigated to detect modulation in the poloidal flow velocity via the motion of turbulent eddies. The technique needs a single-point measurement only, and investigates modulation of the autocorrelation function. In order to evaluate the sensitivity of the method an analytical expression is derived for the relative scatter of the autocorrelation function when the fluctuating signal is composed of random events with a given event rate. Detailed formulas are obtained for the case of identical Gaussian pulses. The result of the calculation allows estimation of the scatter of the autocorrelation function due to both event statistical and detector noise. (c) 2005 American Institute of Physics.