I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties

The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g. with unfavourable ion B ∇ direction. It is characterised by the development of a temperature pedestal while the density remains roughly as in the L-mode. This leads to a confinement improvement above the L-mode l...

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Autores: Ryter, F., Fischer, R., Fuchs, C., Happel, T., McDermott, R. M., Viezzer, Eleonora, Wolfrum, E., Barrera Orte, L., Bernert, M., Burckhart, A., Graça, S. da, Kurzan, B., McCarthy, P., Pütterich, T., Suttrop, W., Willensdorfer, M.
Tipo de recurso: artículo
Estado:Versión enviada para evaluación y publicación
Fecha de publicación:2017
País:España
Institución:Universidad de Sevilla (US)
Repositorio:idUS. Depósito de Investigación de la Universidad de Sevilla
OAI Identifier:oai:idus.us.es:11441/78565
Acceso en línea:https://hdl.handle.net/11441/78565
https://doi.org/10.1088/0029-5515/57/1/016004
Access Level:acceso abierto
Palabra clave:Tokamak
Transport
Pedestal
I-mode
H-mode
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spelling I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement propertiesRyter, F.Fischer, R.Fuchs, C.Happel, T.McDermott, R. M.Viezzer, EleonoraWolfrum, E.Barrera Orte, L.Bernert, M.Burckhart, A.Graça, S. daKurzan, B.McCarthy, P.Pütterich, T.Suttrop, W.Willensdorfer, M.TokamakTransportPedestalI-modeH-modeThe I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g. with unfavourable ion B ∇ direction. It is characterised by the development of a temperature pedestal while the density remains roughly as in the L-mode. This leads to a confinement improvement above the L-mode level which can sometimes reach H-mode values. This regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has been studied again since 2009 taking advantage of the development of new diagnostics and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold, pedestal characteristics and confinement, are independent of the heating method. The power required at the L-I transition exhibits an offset linear density dependence but, in contrast to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be mainly determined by the edge pressure gradient and the comparison between ECRH and NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often evolves gradually over a few confinement times until the transition to H-mode which offers a very interesting situation to study the transport reduction and its link with the pedestal formation. Exploratory discharges in which n = 2 magnetic perturbations have been applied indicate that these can lead to an increase of the I-mode power threshold by flattening the edge pressure at fixed heating input power: more heating power is necessary to restore the required edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in detail.European Commission (EUROfusion 633053)IOP PublishingFísica Atómica, Molecular y NuclearEuropean Commission (EC)2017info:eu-repo/semantics/articleinfo:eu-repo/semantics/submittedVersionapplication/pdfapplication/pdfhttps://hdl.handle.net/11441/78565https://doi.org/10.1088/0029-5515/57/1/016004reponame:idUS. Depósito de Investigación de la Universidad de Sevillainstname:Universidad de Sevilla (US)InglésNuclear Fusion, 57, 016004 (23pp).633053http://iopscience.iop.org/article/10.1088/0029-5515/57/1/016004/metainfo:eu-repo/semantics/openAccessoai:idus.us.es:11441/785652026-06-17T12:51:07Z
dc.title.none.fl_str_mv I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
title I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
spellingShingle I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
Ryter, F.
Tokamak
Transport
Pedestal
I-mode
H-mode
title_short I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
title_full I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
title_fullStr I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
title_full_unstemmed I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
title_sort I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties
dc.creator.none.fl_str_mv Ryter, F.
Fischer, R.
Fuchs, C.
Happel, T.
McDermott, R. M.
Viezzer, Eleonora
Wolfrum, E.
Barrera Orte, L.
Bernert, M.
Burckhart, A.
Graça, S. da
Kurzan, B.
McCarthy, P.
Pütterich, T.
Suttrop, W.
Willensdorfer, M.
author Ryter, F.
author_facet Ryter, F.
Fischer, R.
Fuchs, C.
Happel, T.
McDermott, R. M.
Viezzer, Eleonora
Wolfrum, E.
Barrera Orte, L.
Bernert, M.
Burckhart, A.
Graça, S. da
Kurzan, B.
McCarthy, P.
Pütterich, T.
Suttrop, W.
Willensdorfer, M.
author_role author
author2 Fischer, R.
Fuchs, C.
Happel, T.
McDermott, R. M.
Viezzer, Eleonora
Wolfrum, E.
Barrera Orte, L.
Bernert, M.
Burckhart, A.
Graça, S. da
Kurzan, B.
McCarthy, P.
Pütterich, T.
Suttrop, W.
Willensdorfer, M.
author2_role author
author
author
author
author
author
author
author
author
author
author
author
author
author
author
dc.contributor.none.fl_str_mv Física Atómica, Molecular y Nuclear
European Commission (EC)
dc.subject.none.fl_str_mv Tokamak
Transport
Pedestal
I-mode
H-mode
topic Tokamak
Transport
Pedestal
I-mode
H-mode
description The I-mode is a plasma regime obtained when the usual L-H power threshold is high, e.g. with unfavourable ion B ∇ direction. It is characterised by the development of a temperature pedestal while the density remains roughly as in the L-mode. This leads to a confinement improvement above the L-mode level which can sometimes reach H-mode values. This regime, already obtained in the ASDEX Upgrade tokamak about two decades ago, has been studied again since 2009 taking advantage of the development of new diagnostics and heating possibilities. The I-mode in ASDEX Upgrade has been achieved with different heating methods such as NBI, ECRH and ICRF. The I-mode properties, power threshold, pedestal characteristics and confinement, are independent of the heating method. The power required at the L-I transition exhibits an offset linear density dependence but, in contrast to the L-H threshold, depends weakly on the magnetic field. The L-I transition seems to be mainly determined by the edge pressure gradient and the comparison between ECRH and NBI induced L-I transitions suggests that the ion channel plays a key role. The I-mode often evolves gradually over a few confinement times until the transition to H-mode which offers a very interesting situation to study the transport reduction and its link with the pedestal formation. Exploratory discharges in which n = 2 magnetic perturbations have been applied indicate that these can lead to an increase of the I-mode power threshold by flattening the edge pressure at fixed heating input power: more heating power is necessary to restore the required edge pressure gradient. Finally, the confinement properties of the I-mode are discussed in detail.
publishDate 2017
dc.date.none.fl_str_mv 2017
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/submittedVersion
format article
status_str submittedVersion
dc.identifier.none.fl_str_mv https://hdl.handle.net/11441/78565
https://doi.org/10.1088/0029-5515/57/1/016004
url https://hdl.handle.net/11441/78565
https://doi.org/10.1088/0029-5515/57/1/016004
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Nuclear Fusion, 57, 016004 (23pp).
633053
http://iopscience.iop.org/article/10.1088/0029-5515/57/1/016004/meta
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
application/pdf
dc.publisher.none.fl_str_mv IOP Publishing
publisher.none.fl_str_mv IOP Publishing
dc.source.none.fl_str_mv reponame:idUS. Depósito de Investigación de la Universidad de Sevilla
instname:Universidad de Sevilla (US)
instname_str Universidad de Sevilla (US)
reponame_str idUS. Depósito de Investigación de la Universidad de Sevilla
collection idUS. Depósito de Investigación de la Universidad de Sevilla
repository.name.fl_str_mv
repository.mail.fl_str_mv
_version_ 1869411957060141056
score 15.30478

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