Observations of Fast H-Mode Pedestal Dynamics with New MSE/CER Dual-Spectrum Diagnostic at DIII-D
ORAL
Abstract
Two novel single-channel Czerny-Turner spectrometers [1,2] have been deployed at DIII-D for simultaneous and co-located measurements of the spectrally resolved Motional Stark Effect (MSE) Beam Emission and the Carbon CVI charge exchange emission at high spectral (∆λ=0.13 nm) and temporal resolution (1-5 kHz). High throughput optics (f/#=2.8) allow for good signal-to-noise at high time resolution using fast EMCCD detectors. Measurements in ITER-similar H-mode plasmas show clear toroidal rotation collapse during ELM crashes, accompanied by Sigma/Pi ratio changes over a similar timescale. At these timescales, non-equilibrium neutral beam populations appear to play a large role in pedestal MSE line ratios, as qualitatively predicted by the NOMAD quantum collisional codebase. Complex neutral beam physics have also been observed and successfully reproduced with a physics forward model, revealing a continuum of beam energies that further complicate the MSE spectrum. Tentative simultaneous fits of the magnetic pitch, non-equilibrium populations, and toroidal velocity will be shown.
[1] Albosta R et al.: Rev. Sci. Instrum. 93, 113546 (2022)
[2] Albosta R et al.: Rev. Sci. Instrum. 95, 093519 (2024)
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Publication: - Albosta R et al.: Rev. Sci. Instrum. 93, 113546 (2022)<br>- Albosta R et al.: Rev. Sci. Instrum. 95, 093519 (2024)<br>- Albosta R, Thesis: "Simultaneous Measurement of the Pedestal Magnetic Pitch and Toroidal Velocity...". Department of Physics, University of Wisconsin-Madison (2025)<br>
Presenters
Ryan Albosta
University of Wisconsin - Madison
Authors
Ryan Albosta
University of Wisconsin - Madison
Benedikt Geiger
University of Wisconsin - Madison
George R McKee
University of Wisconsin - Madison
Filipp Khabanov
University of Wisconsin Madison, University of Wisconsin, Madison, University of Wisconsin - Madison
