The low frequency edge oscillation in alcator C-Mod and ASDEX upgrade I-mode

McCarthy, W.; Hubbard, A. E.; Terry, J.; Labombard, B.; Kuang, A.; Bielajew, R.; Hutchinson, I.; Hughes, J. W.; Silvagni, D.; Happel, T.; Gil, L.

doi:10.1088/1361-6587/adbc1e

The low frequency edge oscillation in alcator C-Mod and ASDEX upgrade I-mode

Journal Article · Thu Mar 13 00:00:00 EDT 2025 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/adbc1e· OSTI ID:2530773

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Abstract

The low frequency edge oscillation (LFEO) is a low frequency fluctuation in many plasma quantities in the pedestal region of the I-Mode confinement regime. It is observed on Alcator C-Mod between 10–30 kHz and on ASDEX Upgrade between 5–10 kHz. On both tokamaks it has been previously identified as a geodesic acoustic mode (GAM), however the recent discovery of the edge temperature ring oscillation (ETRO) in a similar frequency and spatial location as the LFEO in I-Modes on EAST has called this identification into question. In this paper we investigate the LFEO on C-Mod and AUG using a variety of different experimental techniques including spectral analysis, magnetic mode number analysis, localization, and direct measurement of the LFEO zonal structure and propagation using a mirror Langmuir probe. This investigation has reconfirmed the identification of the LFEO as a GAM and determined that it has several key differences from the ETRO.

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Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0014264

OSTI ID:: 2530773

Alternate ID(s):: OSTI ID: 2526296

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 4 Vol. 67; ISSN 0741-3335

Publisher:: IOP PublishingCopyright Statement

Country of Publication:: United Kingdom

Language:: English

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