Effect of density on peeling limited pedestals in JET-ILW, MAST-U and TCV and implications for ITER pedestal predictions

Abstract Plasmas with low collisionality and with the pedestal limited by peeling modes have been achieved in JET-ILW, MAST-U and TCV. The achieved electron–electron pedestal collisionality and the achieved ratio between electron separatrix density to pedestal density are in the ranges <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ν</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.3</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> </mml:math> , approaching ITER values. In these conditions, the experimental results show that the pedestal pressure increases with increasing density and no degradation of the pedestal pressure with increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> has been observed. These behaviours are opposite to what observed in ballooning limited pedestals. However, in all three machines, both the increase of the pedestal density and the increase of the separatrix density destabilize the ballooning modes and tend to move the pedestal from being peeling limited to being limited by coupled peeling–ballooning modes. The Europed pedestal predictions have been validated against the experimental results in all the three machines, showing a good qualitative agreement and a reasonable quantitative agreement when approaching ITER-relevant parameters of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ν</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ρ</mml:mi> <mml:mrow/> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> (normalized ion Larmor radius). The Europed predictions have been applied to ITER showing that the instabilities that will limit its pedestal strongly depend on the values of and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> . Nonetheless, assuming type I ELMy H-modes, the ITER pedestal in the Q = 10 scenario will reach <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>≈</mml:mo> <mml:mn>60</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mtext>kPa</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> </jats:i

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Journal
Nuclear Fusion
Published
2026-04-07
DOI
https://doi.org/10.1088/1741-4326/ae5c1c
Primary Topic
Magnetic confinement fusion research
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article
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article

Effect of density on peeling limited pedestals in JET-ILW, MAST-U and TCV and implications for ITER pedestal predictions

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Magnetic confinement fusion research
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Effect of density on peeling limited pedestals in JET-ILW, MAST-U and TCV and implications for ITER pedestal predictions

D. Silvagni, J.M. Fontdecaba, A. Kappatou, E. Kowalska-Strzęciwilk, G. Pucella, K. Imada, R. Scannell, Ewa Pawelec, A. Merle, B. Labit, E. Alessi, H.J. Sun, S. Elmore, E. Giovannozzi, Sam Blackmore, Carine Giroud, A. Czarnecka, Christian Perez von Thun, Ivo Samuel Carvalho, David Keeling, Hampus Nyström, Morten Lennholm, Adriano Stagni, James R Harrison, Pedro Carvalho, Mathias Brix, Andy Meigs, Damian King, Sheena Menmuir, Peter Ryan, Rennan Bianchetti Morales, Domagoj Kos, Mikhail Maslov, Samuli Saarelma, Stuart Scott Henderson, Lorenzo Frassinetti, Nicola Vianello, Sven Wiesen
article en

Abstract

Abstract Plasmas with low collisionality and with the pedestal limited by peeling modes have been achieved in JET-ILW, MAST-U and TCV. The achieved electron–electron pedestal collisionality and the achieved ratio between electron separatrix density to pedestal density are in the ranges <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ν</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.3</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> </mml:math> , approaching ITER values. In these conditions, the experimental results show that the pedestal pressure increases with increasing density and no degradation of the pedestal pressure with increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> has been observed. These behaviours are opposite to what observed in ballooning limited pedestals. However, in all three machines, both the increase of the pedestal density and the increase of the separatrix density destabilize the ballooning modes and tend to move the pedestal from being peeling limited to being limited by coupled peeling–ballooning modes. The Europed pedestal predictions have been validated against the experimental results in all the three machines, showing a good qualitative agreement and a reasonable quantitative agreement when approaching ITER-relevant parameters of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ν</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>ρ</mml:mi> <mml:mrow/> <mml:mrow> <mml:mo>∗</mml:mo> <mml:mrow> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> (normalized ion Larmor radius). The Europed predictions have been applied to ITER showing that the instabilities that will limit its pedestal strongly depend on the values of and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>n</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>sep</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> . Nonetheless, assuming type I ELMy H-modes, the ITER pedestal in the Q = 10 scenario will reach <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>p</mml:mi> <mml:mrow> <mml:mtext>e</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mtext>ped</mml:mtext> </mml:mrow> </mml:mrow> </mml:msubsup> <mml:mo>≈</mml:mo> <mml:mn>60</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mtext>kPa</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> </jats:i

Nuclear FusionVol. 66(5)
ITER (FR), National Agency for New Technologies, Energy and Sustainable Economic Development (IT), University of Opole (PL), Forschungszentrum Jülich (DE), Culham Centre for Fusion Energy (GB), Tokamak Energy (United Kingdom) (GB), Culham Science Centre (GB), Institute of Industrial Organic Chemistry (PL), Max Planck Institute for Plasma Physics (DE), Institute of Plasma Physics and Laser Microfusion (PL), Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati (IT), Instituto Superior de Educação e Ciências (PT), Consorzio per la Ricerca Sanitaria (IT), Institute for the Science and Technology of Plasmas (IT), École Polytechnique Fédérale de Lausanne (CH), University of York (GB), KTH Royal Institute of Technology (SE)
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