Spatiotemporal mode structure of nonlinearly coupled drift wave modes

Abstract

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 10 μs 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.

Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices

“…For example, imaging of the unfiltered light emitted by CSDX in an argon plasma showed fluctuating 2-D structures in the radial vs. poloidal plane, which had a statistically significant correlation coefficient (∼0.5) with local density fluctuations measured by a Langmuir probe. 20,21 More recent passive imaging measurements in CSDX used ArI and ArII line filters and identified coherent modes and multiple instabilities during the route to fully developed turbulence, 22,23 and turbulence in linear devices was also imaged with a fast camera in Mirabelle 24 and LAPD. 25 Fast passive imaging has also been done in the small toroidal device TORPEX using a hydrogen plasma, but without an interference filter.…”

Direct extraction of coherent mode properties from imaging measurements in a linear plasma column

“…64 Each filtered sequence was interpreted as a record of the time evolution of a particular mode and the subsequent analysis showed this evolution to FIG. 10.…”

Spatiotemporal Splitting of Global Eigenmodes due to Cross-Field Coupling via Vortex Dynamics in Drift Wave Turbulence

“…[27], however due to strong parallax in that experiment, it could not be unambiguously verified and studied. Moreover since the radial and axial motion could not be decoupled clearly, the effect of radial coupling was not found.…”

“…Azimuthal FFT decomposition of the camera images is used to obtain azimuthal eigenmodes [27][28][29][30][31][32][33][34][35][36]. Radial profiles of the light fluctuation amplitude and the azimuthal angle (phase) are modeselectively extracted to study the temporal evolution of the 2D structure of eigenmodes.…”