Spatiotemporal mode structure of nonlinearly coupled drift wave modes

This paper presents full cross-section measurements of drift waves in the linear magnetized plasma of the Mirabelle device. Drift wave modes are studied in regimes of weakly developed turbulence. The drift wave modes develop azimuthal space-time structures of plasma density, plasma potential, and visible light fluctuations. A fast camera diagnostic is used to record visible light fluctuations of the plasma column in an azimuthal cross section with a temporal resolution of 10μs corresponding approximately to 10% of the typical drift wave period. Mode coupling and drift wave dispersion are studied by spatiotemporal Fourier decomposition of the camera frames. The observed coupling between modes is compared to calculations of nonlinearly coupled oscillators described by the Kuramoto model

On turbulence-correlation analysis based on correlation reflectometry

Équipe 107 : Physique des plasmas chaudsInternational audienceDrift wave micro-turbulence is the main source of anomalous transport in a tokamak. Correlation reflectometry is a powerful diagnostic tool which provides information on plasma turbulence and subsequently on underlying instability. In this paper, theoretical expressions for the analysis of radial correlation reflectometry (RCR) data are derived. Integral kernels, which convert the correlation function of two microwave reflectometry signals into a correlation function of plasma turbulence and inverse, are discussed. The analytical expression and the method of combining the RCR diagnostic and another local density fluctuation (e.g. Doppler enhanced scattering or heavy ion beam probe) is proposed. The correlation between reflectometry signals and those from other local fluctuation measurements is analysed. The long-range tail of the correlation decays much more gradually than the turbulence correlation, however, it decays faster than that of two microwave reflectometry signals. The way to calculate turbulence wave number spectrum for this case is also proposed

Non-Gaussian properties of global momentum and particle fluxes in a cylindrical laboratory plasma

Non-Gaussian statistical properties of the azimuthally averaged momentum and particle fluxes driven by turbulence have been simultaneously observed in inhomogeneous magnetized plasmas for the first time. We identified the stretched Gaussian distribution of the both fluxes and the transition from the point-wise distribution to averaged ones was confirmed. The change of the particle flux precedes that of the momentum flux, demonstrating that the momentum flux is induced by the relaxation of density gradient. © 2011 American Institute of Physics