Heavy impurities, such as tungsten (W), can exhibit strongly poloidally asymmetric density profiles in rotating or radio frequency heated plasmas. In the metallic environment of JET, the poloidal asymmetry of tungsten enhances its neoclassical transport up to an order of magnitude, so that neoclassical convection dominates over turbulent transport in the core. Accounting for asymmetries in neoclassical transport is hence necessary in the integrated modeling framework. The neoclassical drift kinetic code, NEO [E. Belli and J. Candy, Plasma Phys. Controlled Fusion P50, 095010 (2008)], includes the impact of poloidal asymmetries on W transport. However, the computational cost required to run NEO slows down significantly integrated modeling. A previous analytical formulation to describe heavy impurity neoclassical transport in the presence of poloidal asymmetries in specific collisional regimes [C. Angioni and P. Helander, Plasma Phys. Controlled Fusion 56, 124001 (2014)] is compared in this work to numerical results from NEO. Within the domain of validity of the formula, the factor for reducing the temperature screening due to poloidal asymmetries had to be empirically adjusted. After adjustment, the modified formula can reproduce NEO results outside of its definition domain, with some limitations: When main ions are in the banana regime, the formula reproduces NEO results whatever the collisionality regime of impurities, provided that the poloidal asymmetry is not too large. However, for very strong poloidal asymmetries, agreement requires impurities in the Pfirsch-Schlüter regime. Within the JETTO integrated transport code, the analytical formula combined with the poloidally symmetric neoclassical code NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] predicts the same tungsten profile as NEO in certain cases, while saving a factor of one thousand in computer time, which can be useful in scoping studies. The parametric dependencies of the temperature screening reduction due to poloidal asymmetries would need to be better characterised for this faster model to be extended to a more general applicability.

VL - 25 IS - 1 U1 -FP

U2 -IMT

U5 - 4124380d82634de2c37d95ae7f073ef4 ER - TY - JOUR T1 - First principle integrated modeling of multi-channel transport including Tungsten in JET JF - Nuclear Fusion Y1 - 2018 A1 - Breton, S. A1 - Casson, F. A1 - Bourdelle, C. A1 - Citrin, J. A1 - Baranov, Y. A1 - Camenen, Y. A1 - Challis, C. A1 - Corrigan, G. A1 - J. Garcia A1 - Garzotti, L. A1 - Henderson, S. A1 - Koechl, F. A1 - Militello-Asp, E. A1 - O'Mulane, M. A1 - Putterich, T. A1 - Sertoli, M. A1 - Valisa, M. AB -For the first time, over five confinement times, the self-consistent flux driven time evolution of heat, momentum transport and particle fluxes of electrons and multiple ions including Tungsten (W) is modeled within the integrated modeling platform JETTO [Romanelli M et al PFR 2014], using first principle-based codes: namely, QuaLiKiz [Bourdelle C. et al. PPCF 2016] for turbulent transport and NEO [Belli E A and Candy J PPCF 2008] for neoclassical transport. For a JET-ILW pulse, the evolution of measured temperatures, rotation and density profiles are successfully predicted and the observed W central core accumulation is obtained. The poloidal asymmetries of the W density modfying its neoclassical and turbulent transport are accounted for. Actuators of the W core accumulation are studied: removing the central particle source annihilates the central W accumulation whereas the suppression of the torque reduces significantly the W central accumulation. Finally, the presence of W slightly reduces main ion heat turbulent transport through complex nonlinear interplays involving radiation, effective charge impact on ITG and collisionality.

VL - 58 IS - 9 U1 -FP

U2 -IMT

U5 - 8b217fe93b83353631a28ae3b1981d0a ER - TY - JOUR T1 - Real-time capable first principle based modelling of tokamak turbulent transport JF - Nuclear Fusion Y1 - 2015 A1 - Citrin, J. A1 - Breton, S. A1 - Felici, F. A1 - Imbeaux, F. A1 - Aniel, T. A1 - Artaud, J. F. A1 - Baiocchi, B. A1 - Bourdelle, C. A1 - Camenen, Y. A1 - J. Garcia VL - 55 IS - 9 U1 - FP U2 - CPP-HT U5 - 90cae35de21da646d707098e7f9862de ER -