Investigation of magnetic fluctuations in L-H and H-L transition dynamics on DIII-D

Ashton-Key, T.; Andrew, Y.; Kingham, R.; Kim, E.; Jones, C.; Rhodes, T. L.; Schmitz, L.; Yan, Z.

doi:10.1088/1361-6587/adaaea

Title: Investigation of magnetic fluctuations in L-H and H-L transition dynamics on DIII-D

Journal Article · 24 January 2025 · Plasma Physics and Controlled Fusion

DOI: https://doi.org/10.1088/1361-6587/adaaea · OSTI ID:2506904

^[1];

^[2]; Jones, C. ^[1];

^[3];

^[4]

Imperial College London (United Kingdom)
Coventry University (United Kingdom); Seoul National University (Korea, Republic of)
University of California, Los Angeles, CA (United States)
University of Wisconsin-Madison, WI (United States)

The dynamics of the L-H transition is not fully understood, with many parameters changing the threshold power to enter H-mode and the self-regulation between zonal flows and turbulence in the plasma edge. This paper is primarily a presentation of experimental results for DIII-D L-H and H-L transitions and speculation on the observations made. Power threshold analysis and measurements of pedestal temperatures for these transitions are presented. A comparison is made between an L-H transition and H-L transition of comparable Psep exhibiting oscillatory behaviour, showing symmetry between forward and backward transition dynamics. This paper shows the first observations of magnetic fluctuations during L-H and H-L transitions on DIII-D, and shows that L-H and H-L transitions have similar magnetic fluctuation dynamics. Information geometry analysis has been performed on measurements of plasma density fluctuations, perpendicular plasma velocity fluctuations, and magnetic field fluctuations to investigate the self-regulation and evolution of these variables during the transitions. Perpendicular flow evolution is shown to dominate the transition dynamics in both directions, but self-regulation behaviour is observed between all three variables. A strong correlation between magnetic fluctuation information rate and density fluctuation information rate for these two shots shows the strong influence of magnetic behaviour on both the L-H and H-L transition, and that these transition dynamics necessarily include electromagnetic effects.

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Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FC02-04ER54698; FG02-08ER54999; SC0019352; SC0020287

OSTI ID:: 2506904

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 2 Vol. 67; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Title: Investigation of magnetic fluctuations in L-H and H-L transition dynamics on DIII-D

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