Integrated modelling of neon impact on JET H-mode core plasmas

Marin, Michèle; Citrin, J.; Giroud, C.; Bourdelle, C.; Camenen, Y.; Garzotti, L.; Ho, A.; Sertoli, M.

doi:10.1088/1741-4326/aca469

Cited by 5 publications

(3 citation statements)

References 62 publications

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“…Impurity-induced reduction of ETG modes, together with ITG stabilization by E × B shear and high T i /T e , could be acting synergistically to reduce the transport and improve the global confinement in JPN 96994. Similar results are obtained in highly radiating scenarios at JET [4,5,13], where the modelling identifies in the reduced core transport (via ITG and ETG turbulence stabilization) and in the increased pedestal T i and T e the causes for the improved performance with neon. However the baseline shots presented in this paper have lower neon seeding, lower recycling, lower gas puff, lower edge collisionality and a higher performance with respect to the ones presented in [4], in which the divertor is pushed towards detachment.…”

Section: Transport and Turbulence Analysissupporting

confidence: 79%

“…One technique that can lead to turbulence stabilization is the controlled injection of impurities [2,3]. In fact, it has been demonstrated on different tokamaks that the seeding of impurities (mainly neon) into the plasma can lead to a higher confinement with respect to equivalent unseeded pulses [2][3][4][5][6]. In addition to this, the injection of low-to-mid Z impurities (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Neon seeding effects on two high-performance baseline plasmas on the Joint European Torus

et al. 2023

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We present the JETTO-QuaLiKiz-SANCO fully predictive modelling of two JET-ILW high-performance baseline plasmas, a Ne seeded shot and an equivalent unseeded one. The motivation of the work lies in the experimental observation of a slightly higher confinement and performance of the Ne seeded shot with respect to the unseeded one, despite sharing the same main plasma parameters and heating powers. Moreover, the neon seeded shot shows a lower pedestal electron density and a higher core ion temperature with respect to the unseeded one. Integrated modelling is performed in order to understand if the cause of the improved confinement has to be ascribed to the improved pedestal parameters with neon seeding or if an impurity-induced turbulence stabilization is at play. The QuaLiKiz transport model is used for predicting the electron density, electron and ion temperatures and rotation in the core up to the pedestal top, while the pedestal is empirically modelled to reproduce the experimental kinetic profiles. The thermal diffusivities of the two shots, computed by QuaLiKiz, are compared, as well as the turbulence spectra, suggesting that the reduced transport found in the neon seeded shot is due in part to the stabilization of ITG and ETG modes. Further modelling is performed in order to disentangle the neon seeding effects, which are a direct effect on the turbulence stabilization and an indirect effect on the pedestal parameters. The results suggest that the improved performance with neon is due to a combination of turbulence stabilization and improved pedestal parameters.

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Section: Transport and Turbulence Analysissupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Neon seeding effects on two high-performance baseline plasmas on the Joint European Torus

et al. 2023

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“…Recent developments in integrated modelling have been dedicated to the description of impurity transport [17][18][19][20][21][22][23][24], including the evolution of the background plasma with radiative losses by impurities [25][26][27]. However, some limitations are present either because the boundary condition is set well inside the confined plasma, or because empirical impurity transport coefficients are used at the edge.…”

Section: Introductionmentioning

confidence: 99%

Full-radius integrated modelling of ASDEX Upgrade L-modes including impurity transport and radiation

Fajardo,

Angioni,

Dux

et al. 2024

Nucl. Fusion

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An integrated framework that demonstrates multi-species, multi-channel modelling capabilities for the prediction of impurity density profiles and their feedback on the main plasma through radiative cooling and fuel dilution is presented. It combines all presently known theoretical elements in the local description of quasilinear turbulent and neoclassical impurity transport, using the models TGLF-SAT2 and FACIT. These are coupled to the STRAHL code for impurity sources and radiation inside the ASTRA transport solver. The workflow is shown to reproduce experimental results in full-radius L-mode modelling. In particular, a set of ASDEX Upgrade L-modes with differing heating power mixtures and plasma currents are simulated, including boron (B) and tungsten (W) as intrinsic impurities. The increase of predicted confinement with higher current and the reduction of core W peaking with higher central wave heating are demonstrated. Furthermore, a highly radiative L-mode scenario featuring an X-point radiator (XPR) with two intrinsic (B, W) and one seeded argon (Ar) species is simulated, and its measured radiated power and high confinement are recovered by the modelling. The stabilizing effect of impurities on turbulence is analyzed and a simple model for the peripheral X-point radiation is introduced. A preliminary full-radius simulation of an H-mode phase of this same discharge, leveraging recent work on the role of the E×B shearing at the edge, shows promising results.

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Simulation of neoclassical heavy impurity transport in ASDEX Upgrade with applied 3D magnetic fields using the nonlinear MHD code JOREK

Korving,

Mitterauer,

Huijsmans

et al. 2024

Physics of Plasmas

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Accumulation of heavy impurities in the tokamak core is detrimental for its performance and can lead to disruption of the plasma. In small to medium-sized tokamaks the effective neoclassical transport in the pedestal is typically oriented radially inward. In larger tokamaks—e.g., ITER—where the temperature gradient is higher and density gradients are lower due to the need to operate in a radiative divertor regime, the neoclassical transport is predicted to be outwards. The models are derived for axisymmetric quasi-steady-state plasmas. Applied 3D magnetic fields, i.e., Resonant Magnetic Perturbation (RMPs) as they are used to suppress Edge Localized Modes (ELMs), have experimentally been observed in AUG to enhance the outflow of heavy impurities in the pedestal. There is no model that can predict neoclassical heavy impurity transport in these ergodized 3D magnetic fields self-consistently. In this contribution, we present our kinetic tungsten transport simulation for an ASDEX Upgrade plasma with applied RMPs. Our model based on Hoelzl et al. [Nucl. Fusion 61, 065001 (2021)], van Vugt et al. [Phys. Plasmas 26, 042508 (2019)], and Korving et al. [Phys. Plasmas 30, 042509 (2023)] utilizes a full-orbit pusher, ionization, recombination, effective line, and continuum radiation and neoclassical collisions with the background plasma. The effective collisional radiative rates are from the OpenADAS database, the neoclassical collision operator uses the framework of Homma et al. [J. Comput. Phys. 250, 206–223 (2013)] and Homma et al. [Nucl. Fusion 56, 036009 (2016)]. We show that the adopted collision operator produces neoclassical transport within a satisfactory degree of accuracy. A sufficiently high RMP current causes an increase in tungsten diffusion in the pedestal by a factor of 2. We compare the average radial transport between axisymmetric and 3D RMP scenarios in the pedestal region. RMPs enhance the pedestal permeability for impurities, which results in enhanced transport. In addition to the enhanced transport, some of W is found to be trapped in 3D potential wells in the scrape-off layer. Due to the lack of suitable diagnostics for W in the pedestal, we investigate and suggest that argon can be an adequate substitute in experiments for model validation and further understanding impurity transport in scenarios with applied 3D magnetic fields. With the newly developed neutral model [Korving et al., Phys. Plasmas 30, 042509 (2023)], we can combine the interaction in the divertor with the 3D RMPs to model the tungsten transport from the divertor toward the core of the plasma.

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Integrated modelling of neon impact on JET H-mode core plasmas

Cited by 5 publications

References 62 publications

Neon seeding effects on two high-performance baseline plasmas on the Joint European Torus

Neon seeding effects on two high-performance baseline plasmas on the Joint European Torus

Full-radius integrated modelling of ASDEX Upgrade L-modes including impurity transport and radiation

Simulation of neoclassical heavy impurity transport in ASDEX Upgrade with applied 3D magnetic fields using the nonlinear MHD code JOREK

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