Relation between separatrix electron density and divertor neutral pressure in Alcator C-Mod, ASDEX Upgrade and JET H-mode plasmas

ORAL

Abstract

The separatrix electron density ne,sep is an important plasma parameter that influences H-mode confinement, detachment achievement, ELM avoidance and sets a limit to H-mode operation. Therefore, quantitative prediction of ne,sep is crucial for a meaningful assessment of a core-edge-SOL integrated scenario solution in next-step devices. For this purpose, assembling a multi-machine database is pivotal to both developing simple physics models that could explain the main parameter dependencies of ne,sep and benchmarking state-of-the-art SOL codes.

In this work, a machine-agnostic procedure to evaluate ne,sep for ELMy and no-ELM H-mode plasmas is presented and used to assemble a ne,sep and Te,sep database which includes Alcator C-Mod, ASDEX Upgrade and JET data. The analysis procedure, which is applied in the same way in all devices, relies on Thomson Scattering (TS) measurements and on the assumption of SOL parallel transport being dominated by Spitzer-Härm electron conduction, see e.g. [1, 2, 3]. It is found that, across all devices, a similar relationship between ne,sep and the divertor neutral pressure p0,div is observed, namely ne,sep ∝ p0,div0.25±0.06. Additionally, upon normalizing ne,sep to the obtained p0,div dependency, no remaining correlation with the plasma current is found. These observations are in agreement with the expected dependencies from the 2-point model [4, 5, 6], and suggest that in the present dataset the upstream separatrix density is mainly determined by divertor target recycling.

[1] S.K. Erents et al., Nucl. Fusion 40, 295 (2000)

[2] A. Leonard et al., Nucl. Fusion 57, 086033 (2017)

[3] T. Eich et al., Nucl. Fusion 61, 086017 (2021)

[4] P. C. Stangeby, Plasma Phys. Control. Fusion 60, 044022 (2018)

[5] S.I. Krasheninnikov et al., Phys. Plasmas 23, 055602 (2016)

[6] A. Kallenbach et al., Plasma Phys. Control. Fusion 60, 045006 (2018)

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Publication: D Silvagni et al., submitted to Nuclear Materials and Energy

Presenters

  • Davide Silvagni

    • Max-Planck-Institut für Plasmaphysik

Authors

  • Davide Silvagni

    • Max-Planck-Institut für Plasmaphysik

  • Ondrej Grover

    • Max-Planck-Institute for Plasmaphysics

  • Adriano Stagni

    • Consorzio RFX Padova

  • Jerry W Hughes

    • MIT Plasma Science and Fusion Center
    • Massachusetts Institute of Technology

  • Marco Andrés Miller

    • MIT Plasma Science and Fusion Center
    • MIT PSFC

  • Bartosz Lomanowski

    • Oak Ridge National Laboratory

  • Guido Ciraolo

    • CEA, IRFM

  • Michael G Dunne

    • Max–Planck–Institut fuer Plasmaphysik

  • Thomas Eich

    • Commonwealth Fusion Systems

  • Lorenzo Frassinetti

    • Fusion Plasma Physics, EECS, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden

  • Carine Giroud

    • United Kingdom Atomic Energy Authority, Culham Campus, Abingdon, UK
    • United Kingdom Atomic Energy Authority, Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK
    • UKAEA (United Kingdom Atomic Energy Authority), Culham Campus, Abingdon, Oxfordshire, OX14 3DB, UK

  • Ionut Jepu

    • UKAEA

  • Arne Kallenbach

    • Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
    • Max-Planck-Institute for Plasmaphysics
    • Max-Planck-Institute for Plasmaphysics (Garching)

  • Anu Kirjasuo

    • VTT

  • Adam Q Kuang

    • Commonwealth Fusion Systems

  • Teobaldo Luda di Cortemiglia

    • Max-Planck-Institut für Plasmaphysik

  • Christian Perez von Thun

    • Institute of Plasma Physics and Laser Microfusion

  • Thomas Pütterich

    • Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany
    • Max-Planck-Institute for Plasmaphysics (Garching)

  • Hongjuan Sun

    • United Kingdom Atomic Energy Authority, Culham Campus, Abingdon, UK

  • Hartmut Zohm

    • Max Planck Institute for Plasma Physics