Peculiarity of highly radiating multi-impurity seeded H-mode plasmas on JET with ITER-like wall

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Physica Scripta, Volume 2020, issue T171
On JET with fully metallic first wall, highly radiative conditions with N2, Ne and Ar as well as their mixture as radiators are approached in high density H-mode plasmas. The confinement increases from H 98(y,2) = 0.65 in unseeded pulses with γ rad ∼ 30% to a value of H 98(y,2) = 0.75 at γ rad ∼ 50% with N2 injection. A degradation of the pedestal profile is compensated by steeper core n e and T e profiles. Further increase of γ rad with increase of the N2 seeding rate leads to a moderate confinement degradation which can be avoided by applying of combined impurity seeding. The enhancement of the plasma performance for the radiation fractions beyond 55% with the maximum value of H 98(y,2) = 0.78 is reached with combined N2 + Ne and N2 + Ar impurity injections. The observed intense, strongly localized radiation at the X-point inside the confined plasma in the scenarios with the highest radiated power fraction is interlinked to complete divertor detachment. In the JET-ILW, the X-point radiation is stable, reproducible and reversible.
| openaire: EC/H2020/633053/EU//EUROfusion
Detachment, Divertors, Impurities in plasmas, Power exhaust, Radiation, Tokamaks
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Huber, A, Wischmeier, M, Bernert, M, Wiesen, S, Glöggler, S, Aleiferis, S, Brezinsek, S, Calabro, G, Carvalho, P, Huber, V, Sergienko, G, Solano, E R, Giroud, C, Groth, M, Jachmich, S, Linsmeier, C, Matthews, G F, Meigs, A G, Mertens, P, Sertoli, M, Silburn, S & Telesca, G 2020, ' Peculiarity of highly radiating multi-impurity seeded H-mode plasmas on JET with ITER-like wall ', Physica Scripta, vol. T171, no. 1, 014055 .