ELM-free H-mode phase and decoupling of peeling-ballooning stability boundary in the MAST Upgrade tokamak

the MAST Upgrade Team

doi:10.1088/1361-6587/ad877c

ELM-free H-mode phase and decoupling of peeling-ballooning stability boundary in the MAST Upgrade tokamak

the MAST Upgrade Team

Fusion Energy Division

Research output: Contribution to journal › Article › peer-review

Abstract

A linear magnetohydrodynamic (MHD) peeling-ballooning stability analysis of the edge-localized mode (ELM)-free phase of a MAST Upgrade (MAST-U) H-mode plasma is presented. In contrast to other similar discharges, #47018 is found to have a significantly higher and wider pedestal during its ELM-free H-mode phase that lasts for approximately 80 ms; this is made possible by the reduced core MHD mode activity on the q = 2 surface. During this period, there is sustained decoupling of peeling and ballooning branches of the stability boundary on J-α space, opening an access channel to the second stability regime with higher peaks in pedestal current density J N , ped and pressure gradient (α). Such decoupling of the stability boundary has not previously been observed in MAST-U H-modes, and if such a condition can be readily reproduced, it opens a wide range of opportunities for MAST-U to explore low-collisionality peeling-limited pedestal regimes as well as advanced scenarios such as quiescent H-modes that are relevant to future reactors such as STEP and ITER.

Original language	English
Article number	125011
Journal	Plasma Physics and Controlled Fusion
Volume	66
Issue number	12
DOIs	https://doi.org/10.1088/1361-6587/ad877c
State	Published - Dec 2024

Funding

This research is funded by US Department of Energy, through General Atomics (Contract Number DE-SC0018990) and Oak Ridge National Laboratory (Contract Number DE-AC05-00OR22725), as well as UKRI Energy Programme through EPSRC, Grant Numbers EP/T012250/1 and EP/R034737/1.

Funders	Funder number
U.S. Department of Energy
UK Research and Innovation
General Atomics	DE-SC0018990
General Atomics
Oak Ridge National Laboratory	DE-AC05-00OR22725
Oak Ridge National Laboratory
Engineering and Physical Sciences Research Council	EP/T012250/1, EP/R034737/1
Engineering and Physical Sciences Research Council

Keywords

ELMs
MAST Upgrade
pedestal stability
spherical tokamak

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1088/1361-6587/ad877c

Cite this

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title = "ELM-free H-mode phase and decoupling of peeling-ballooning stability boundary in the MAST Upgrade tokamak",

abstract = "A linear magnetohydrodynamic (MHD) peeling-ballooning stability analysis of the edge-localized mode (ELM)-free phase of a MAST Upgrade (MAST-U) H-mode plasma is presented. In contrast to other similar discharges, #47018 is found to have a significantly higher and wider pedestal during its ELM-free H-mode phase that lasts for approximately 80 ms; this is made possible by the reduced core MHD mode activity on the q = 2 surface. During this period, there is sustained decoupling of peeling and ballooning branches of the stability boundary on J-α space, opening an access channel to the second stability regime with higher peaks in pedestal current density J N , ped and pressure gradient (α). Such decoupling of the stability boundary has not previously been observed in MAST-U H-modes, and if such a condition can be readily reproduced, it opens a wide range of opportunities for MAST-U to explore low-collisionality peeling-limited pedestal regimes as well as advanced scenarios such as quiescent H-modes that are relevant to future reactors such as STEP and ITER.",

keywords = "ELMs, MAST Upgrade, pedestal stability, spherical tokamak",

author = "{the MAST Upgrade Team} and K. Imada and Osborne, {T. H.} and S. Saarelma and A. Kirk and S. Blackmore and M. Knolker and R. Scannell and Snyder, {P. B.} and C. Vincent and Wilson, {H. R.}",

note = "Publisher Copyright: {\textcopyright} 2024 The Author(s). Published by IOP Publishing Ltd.",

year = "2024",

month = dec,

doi = "10.1088/1361-6587/ad877c",

language = "English",

volume = "66",

journal = "Plasma Physics and Controlled Fusion",

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TY - JOUR

T1 - ELM-free H-mode phase and decoupling of peeling-ballooning stability boundary in the MAST Upgrade tokamak

AU - the MAST Upgrade Team

AU - Imada, K.

AU - Osborne, T. H.

AU - Saarelma, S.

AU - Kirk, A.

AU - Blackmore, S.

AU - Knolker, M.

AU - Scannell, R.

AU - Snyder, P. B.

AU - Vincent, C.

AU - Wilson, H. R.

PY - 2024/12

Y1 - 2024/12

N2 - A linear magnetohydrodynamic (MHD) peeling-ballooning stability analysis of the edge-localized mode (ELM)-free phase of a MAST Upgrade (MAST-U) H-mode plasma is presented. In contrast to other similar discharges, #47018 is found to have a significantly higher and wider pedestal during its ELM-free H-mode phase that lasts for approximately 80 ms; this is made possible by the reduced core MHD mode activity on the q = 2 surface. During this period, there is sustained decoupling of peeling and ballooning branches of the stability boundary on J-α space, opening an access channel to the second stability regime with higher peaks in pedestal current density J N , ped and pressure gradient (α). Such decoupling of the stability boundary has not previously been observed in MAST-U H-modes, and if such a condition can be readily reproduced, it opens a wide range of opportunities for MAST-U to explore low-collisionality peeling-limited pedestal regimes as well as advanced scenarios such as quiescent H-modes that are relevant to future reactors such as STEP and ITER.

AB - A linear magnetohydrodynamic (MHD) peeling-ballooning stability analysis of the edge-localized mode (ELM)-free phase of a MAST Upgrade (MAST-U) H-mode plasma is presented. In contrast to other similar discharges, #47018 is found to have a significantly higher and wider pedestal during its ELM-free H-mode phase that lasts for approximately 80 ms; this is made possible by the reduced core MHD mode activity on the q = 2 surface. During this period, there is sustained decoupling of peeling and ballooning branches of the stability boundary on J-α space, opening an access channel to the second stability regime with higher peaks in pedestal current density J N , ped and pressure gradient (α). Such decoupling of the stability boundary has not previously been observed in MAST-U H-modes, and if such a condition can be readily reproduced, it opens a wide range of opportunities for MAST-U to explore low-collisionality peeling-limited pedestal regimes as well as advanced scenarios such as quiescent H-modes that are relevant to future reactors such as STEP and ITER.

KW - ELMs

KW - MAST Upgrade

KW - pedestal stability

KW - spherical tokamak

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U2 - 10.1088/1361-6587/ad877c

DO - 10.1088/1361-6587/ad877c

M3 - Article

AN - SCOPUS:85209374357

SN - 0741-3335

VL - 66

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

IS - 12

M1 - 125011

ER -

ELM-free H-mode phase and decoupling of peeling-ballooning stability boundary in the MAST Upgrade tokamak

Abstract

Funding

Keywords

UN SDGs

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