Experimental study of drift-wave saturation in quadrupole geometry

Abstract

We describe measurements of non-linear interactions between drift waves and law-frequency flute-like modes in the UMIST quadrupole. We present experimental measurements of the bispectrum, and a l s ~ results from a technique of "amplitude correlation" which we believe provides a more direct way of determining the direction of the energy flow. On the basis of the results we propose a model olenergy flaw in the drift-wave spectrum: the observed spectrum contains regions af growth at high frequency and damping at low frequency, with flow dawn the spectrum via a cascade mediated by the flute-like modes.

Study of intermittent small-scale turbulence in Wendelstein 7-AS plasmas during controlled confinement transitions

“…Our technique is similar to the one introduced in Refs. [20,21], it is fundamentally different from the standard signal correlation. This correlation calculation can be done between band autopower signals at different frequencies as illustrated in The reduction in frequency range from good to bad confinement implies that the speed U (magnitude of the poloidal velocity U) of the density fluctuations decreases.…”

Experimental progress on zonal flow physics in toroidal plasmas

“…Energy transfer between disparate scale waves or fluctuations has been studied using nonlinear energy transfer [37] and autocorrelation analyses [38] in H1-heliac. These analyses have shown the evidence of inverse cascade in both frequency and wavenumber domains, and difference of energy transfer structure between L-and H-mode [17,26,39].…”

MeanE×Bflows and GAM-like oscillations in the H-1 heliac

“…The second term on the right-hand side of equation 2 The m = 1, n = 1(2) spectral feature observed in the fluctuations of the floating potential ( figure 4(a)) is spectrally coupled to the m = 0 low-frequency oscillations at f ≈ 0. The analysis of this spectral connection is performed in the frequency domain using the amplitude correlation technique [25]. This technique has been successfully used to analyse spectral transfer in H-1 [14,17].…”