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...
| Authors: | ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; |
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| Format: | Article |
| Status: | Submitted version |
| Publication date: | 2017 |
| Country: | España |
| Institution: | Universidad de Sevilla (US) |
| Repository: | idUS. Depósito de Investigación de la Universidad de Sevilla |
| OAI Identifier: | oai:idus.us.es:11441/78565 |
| Online Access: | https://hdl.handle.net/11441/78565 https://doi.org/10.1088/0029-5515/57/1/016004 |
| Access Level: | Open access |
| Keyword: | Tokamak Transport Pedestal I-mode H-mode |
| _version_ | 1878735664233578497 |
|---|---|
| author | Ryter, F. |
| 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 |
| author_browse | Barrera Orte, L. Bernert, M. Burckhart, A. Fischer, R. Fuchs, C. Graça, S. da Happel, T. Kurzan, B. McCarthy, P. McDermott, R. M. Pütterich, T. Ryter, F. Suttrop, W. Viezzer, Eleonora Willensdorfer, M. Wolfrum, E. |
| 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 |
| collection | idUS. Depósito de Investigación de la Universidad de Sevilla |
| 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. |
| eu_rights_str_mv | openAccess |
| format | article |
| id | ES_8135fcceca1ff9187c6d7838c06b2ef7 |
| institution | Universidad de Sevilla (US) |
| instname_str | Universidad de Sevilla (US) |
| network_acronym_str | ES |
| network_name_str | España |
| oai_identifier_str | oai:idus.us.es:11441/78565 |
| publishDate | 2017 |
| publishDateSort | 2017 |
| publisher | IOP Publishing |
| publisherStr | IOP Publishing |
| reponame_str | idUS. Depósito de Investigación de la Universidad de Sevilla |
| spelling | I-mode studies at ASDEX Upgrade: L-I and I-H transitions, pedestal and confinement properties 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. Tokamak Transport Pedestal I-mode H-mode 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. European Commission (EUROfusion 633053) IOP Publishing https://hdl.handle.net/11441/78565 https://doi.org/10.1088/0029-5515/57/1/016004 |
| 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 |
| status_str | submittedVersion |
| title | 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_short | 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 |
| topic | Tokamak Transport Pedestal I-mode H-mode |
| topic_facet | Tokamak Transport Pedestal I-mode H-mode |
| url | https://hdl.handle.net/11441/78565 https://doi.org/10.1088/0029-5515/57/1/016004 |