Characterization of edge and scrape-off layer fluctuations using the fast Li-BES system on COMPASS

Abstract

Recently the Li-Beam Emission Spectroscopy (Li-BES) system on COMPASS has reached its full diagnostic power in terms of routine automatic operation in any kind of plasma scenarios and it is normally used as a standard tool for reconstruction of ultra fast density profiles in the edge region of COMPASS plasmas. The purpose of this study is to investigate the advantages and limitations of the COMPASS Li-BES system in characterizing plasma electron density fluctuations. We show how the atomic physics of plasma-beam interactions can affect the interpretation of the measurement at different radial positions and for different electron density profiles. We also demonstrate the usability of generalized sequential probability ratio test for automatic event detection. Using non-perturbative diagnostic, we verify the validity of the stochastic Garcia-model for scrape-off layer filaments and accompanying holes (density deficits).

arXiv commentsuggestions from the coauthors included some text added to explain fig. 9

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Cited by in corpus (4)

• Theory-based scaling laws of near and far scrape-off layer widths in single-null L-mode discharges
• Stochastic modelling of blob-like plasma filaments in the scrape-off layer: Theoretical foundation
• Numerical turbulence simulations of intermittent fluctuations in the scrape-off layer of magnetized plasmas
• Deviations from spectral Dirac comb due to semiperiodic pulses