On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade
The maximum achievable density in a tokamak is restricted by the so-called density limit. In this contribution, we observe that a MARFE precedes the final chain of events leading to disruption in ramp up L-mode discharges, resulting in strong power dissipation and plasma cooling, which likely makes...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2025-01-01
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| Series: | Nuclear Fusion |
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| Online Access: | https://doi.org/10.1088/1741-4326/adeda1 |
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| author | G. Grenfell M. Griener M. Bernert J. Adamek D. Brida M. Faitsch P. Manz B.Ph. van Milligen U. Stroth the ASDEX Upgrade Team the EUROfusion Tokamak Exploitation Team |
| author_facet | G. Grenfell M. Griener M. Bernert J. Adamek D. Brida M. Faitsch P. Manz B.Ph. van Milligen U. Stroth the ASDEX Upgrade Team the EUROfusion Tokamak Exploitation Team |
| author_sort | G. Grenfell |
| collection | DOAJ |
| description | The maximum achievable density in a tokamak is restricted by the so-called density limit. In this contribution, we observe that a MARFE precedes the final chain of events leading to disruption in ramp up L-mode discharges, resulting in strong power dissipation and plasma cooling, which likely makes the plasma unstable to MHD modes. However, this phase is preceded by an initial cooling governed by enhanced radial transport due to higher fluctuations and a more favorable cross-phase for transport, which likely impacts the MARFE formation. The increase in radial turbulent transport near the separatrix is primarily observed following the detachment of the outer divertor. This occurs when an X-point radiator forms and the edge collisionality rises, indicating that the increased collisionality influences the turbulence characteristics in the plasma boundary. The causal connection between the events that precede the disruption is discussed. |
| format | Article |
| id | doaj-art-4e1bbe6ff1364b06ad366fcfc8df2d3b |
| institution | DOAJ |
| issn | 0029-5515 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Nuclear Fusion |
| spelling | doaj-art-4e1bbe6ff1364b06ad366fcfc8df2d3b2025-08-20T02:40:58ZengIOP PublishingNuclear Fusion0029-55152025-01-0165808602310.1088/1741-4326/adeda1On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX UpgradeG. Grenfell0https://orcid.org/0000-0003-0107-5787M. Griener1https://orcid.org/0000-0003-2953-536XM. Bernert2https://orcid.org/0000-0003-1131-0867J. Adamek3https://orcid.org/0000-0001-8562-1233D. Brida4M. Faitsch5https://orcid.org/0000-0002-9809-7490P. Manz6https://orcid.org/0000-0002-5724-0174B.Ph. van Milligen7https://orcid.org/0000-0001-5344-6274U. Stroth8https://orcid.org/0000-0003-1104-2233the ASDEX Upgrade Teamthe EUROfusion Tokamak Exploitation TeamMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, GermanyMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, GermanyMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, GermanyInstitute of Plasma Physics of the CAS , Za Slovankou 3, 182 00 Prague 8, Czech RepublicMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, GermanyMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, GermanyInstitute of Physics, University of Greifswald , Felix-Hausdorff-Str. 6, 17489 Greifswald, GermanyNational Fusion Laboratory, CIEMAT , Avda. Complutense 40, 28040 Madrid, SpainMax-Planck-Institut fur Plasmaphysik , Boltzmannstr. 2, Garching, Germany; Physics Department, TUM School of Natural Sciences, Technical University of Munich , 85748 Garching, GermanyThe maximum achievable density in a tokamak is restricted by the so-called density limit. In this contribution, we observe that a MARFE precedes the final chain of events leading to disruption in ramp up L-mode discharges, resulting in strong power dissipation and plasma cooling, which likely makes the plasma unstable to MHD modes. However, this phase is preceded by an initial cooling governed by enhanced radial transport due to higher fluctuations and a more favorable cross-phase for transport, which likely impacts the MARFE formation. The increase in radial turbulent transport near the separatrix is primarily observed following the detachment of the outer divertor. This occurs when an X-point radiator forms and the edge collisionality rises, indicating that the increased collisionality influences the turbulence characteristics in the plasma boundary. The causal connection between the events that precede the disruption is discussed.https://doi.org/10.1088/1741-4326/adeda1tokamakdensity limitplasma turbulenceMARFELangmuir probeX-point radiator |
| spellingShingle | G. Grenfell M. Griener M. Bernert J. Adamek D. Brida M. Faitsch P. Manz B.Ph. van Milligen U. Stroth the ASDEX Upgrade Team the EUROfusion Tokamak Exploitation Team On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade Nuclear Fusion tokamak density limit plasma turbulence MARFE Langmuir probe X-point radiator |
| title | On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade |
| title_full | On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade |
| title_fullStr | On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade |
| title_full_unstemmed | On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade |
| title_short | On the evolution of profiles and fluctuations towards the L-mode density limit in ASDEX Upgrade |
| title_sort | on the evolution of profiles and fluctuations towards the l mode density limit in asdex upgrade |
| topic | tokamak density limit plasma turbulence MARFE Langmuir probe X-point radiator |
| url | https://doi.org/10.1088/1741-4326/adeda1 |
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