Estimation of wavenumber spectra of fluctuations by using fixed probes

A spectral analysis technique is studied with respect to a stationary and homogeneous random field. The differential coefficients of the covariance function of the field, represented by an analytic signal, is related to its wavenumber spectrum moment. It is shown that the covariance function evaluated by using a pair of fixed probes with an appropriately small separation may provide good estimators of the mean wavenumber and the wavenumber spectral width. This method of measurement may be useful for the experimental study of plasma turbulence. (author)