High resolution density pedestal measurements during edge localized modes by short-pulse reflectometry in the TCV tokamak
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21ja042_full.pdf
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4.83 MB
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5633af294870538909cafd55089c9203
Author(s)
Molina Cabrera, Pedro A.
Labit, B.
Coda, S.
Porte, L.
Date Issued
December 2020
Journal
Plasma Physics and Controlled Fusion
Publisher
IOP
Abstract
This publication presents high spatio-temporal resolution (mm/μs) density profile measurements of the pedestal top during type I, III, and small edge localized mode (ELM) H-mode plasmas in the Tokamak à Configuration Variable (TCV). These measurements were performed using a novel short-pulse reflectometer. Average inter-ELM density profiles are obtained via conditional averaging using the Dα trace as ELM indicator. Changes to the pedestal density profile gradients prior to type-III ELMs reveal unique pedestal dynamics leading to the ELM crash which can provide important experimental data for validation of non-linear MHD ELM simulations. The small-ELM scenario is found to feature a ∼25-35 kHz quasi-coherent density fluctuation near the separatrix rho_psi ∼0.993-1.05 not observed during a similar type-I ELM discharge. This oscillation is also found in low-field-side magnetic pick- up probes displaying a ballooning character and n=+1 toroidal mode number. This oscillation could help explain the markedly different pedestal dynamics observed in the small-ELM regime.
Description
Submitted for publication in Plasma Physics and Controlled Fusion
MIT Department
Massachusetts Institute of Technology. Plasma Science and Fusion Center
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1088/1361-6587/ac0797
