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-Schl{\"u}ter 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.

}, doi = {10.1063/1.5019275}, author = {Breton, S. and Casson, F. J. and Bourdelle, C. and Angioni, C. and Belli, E. and Camenen, Y. and Citrin, J. and Garbet, X. and Sarazin, Y. and Sertoli, M. and JET Contributors} } @article {4051, title = {First principle integrated modeling of multi-channel transport including Tungsten in JET}, journal = {Nuclear Fusion}, volume = {58}, year = {2018}, pages = {096003}, abstract = {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.

}, doi = {10.1088/1741-4326/aac780}, author = {Breton, S. and Casson, F. and Bourdelle, C. and Citrin, J. and Baranov, Y. and Camenen, Y. and Challis, C. and Corrigan, G. and J. Garcia and Garzotti, L. and Henderson, S. and Koechl, F. and Militello-Asp, E. and O{\textquoteright}Mulane, M. and Putterich, T. and Sertoli, M. and Valisa, M.} } @article {4079, title = {Fast H isotope and impurity mixing in ion-temperature-gradient turbulence}, journal = {Nuclear Fusion}, volume = {58}, year = {2018}, pages = {076028}, abstract = {In ion-temperature-gradient (ITG) driven turbulence, the resonance condition leads to ion particle turbulent transport coefficients significantly larger than electron particle turbulent transport coefficients. This is shown in nonlinear gyrokinetic simulations and explained by an analytical quasilinear model. It is then illustrated by JETTO-QuaLiKiz integrated modelling. Large ion particle transport coefficients implies that the ion density profiles are uncorrelated to the corresponding ion source, allowing peaked isotope density profiles even in the absence of core source. This also implies no strong core accumulation of He ash. Furthermore, the relaxation time of the individual ion profiles in a multi-species plasma can be significantly faster than the total density profile relaxation time which is constrained by the electrons. This leads to fast isotope mixing and fast impurity transport in FM regimes. In trapped-electron- mode (TEM) turbulence, in presence of electron heating about twice the ion heating, the situation is the inverse: ion particle turbulent transport coefficients are smaller than their electron counterpart.}, doi = {10.1088/1741-4326/aacd57}, author = {Bourdelle, C. and Camenen, Y. and Citrin, J. and Marin, M. and Casson, F. J. and Kochl, F. and Maslov, M. and JET Contributors} } @article {3899, title = {Tractable flux-driven temperature, density, and rotation profile evolution with the quasilinear gyrokinetic transport model QuaLiKiz}, journal = {Plasma Physics and Controlled Fusion}, volume = {59}, year = {2017}, pages = {124005}, abstract = {Quasilinear turbulent transport models are a successful tool for prediction of core tokamak plasma profiles in many regimes. Their success hinges on the reproduction of local nonlinear gyrokinetic fluxes. We focus on significant progress in the quasilinear gyrokinetic transport model QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036), which employs an approximated solution of the mode structures to significantly speed up computation time compared to full linear gyrokinetic solvers. Optimisation of the dispersion relation solution algorithm within integrated modelling applications leads to flux calculations x10 6-7 faster than local nonlinear simulations. This allows tractable simulation of flux-driven dynamic profile evolution including all transport channels: ion and electron heat, main particles, impurities, and momentum. Furthermore, QuaLiKiz now includes the impact of rotation and temperature anisotropy induced poloidal asymmetry on heavy impurity transport, important for W-transport applications. Application within the JETTO integrated modelling code results in 1 s of JET plasma simulation within 10 h using 10 CPUs. Simultaneous predictions of core density, temperature, and toroidal rotation profiles for both JET hybrid and baseline experiments are presented, covering both ion and electron turbulence scales. The simulations are successfully compared to measured profiles, with agreement mostly in the 5\%{\textendash}25\% range according to standard figures of merit. QuaLiKiz is now open source and available at www.qualikiz.com.}, doi = {10.1088/1361-6587/aa8aeb}, url = {https://arxiv.org/abs/1708.01224}, author = {Citrin, J. and Bourdelle, C. and Casson, F. J. and Angioni, C. and Bonanomi, N. and Camenen, Y. and Garbet, X. and Garzotti, L. and Gorler, T. and Gurcan, O. D. and Koechl, F. and Imbeaux, F. and Linder, O. and van de Plassche, K. and Strand, P. and Szepesi, G. and JET Contributors} } @article {2819, title = {Real-time capable first principle based modelling of tokamak turbulent transport}, journal = {Nuclear Fusion}, volume = {55}, year = {2015}, pages = {092001}, doi = {10.1088/0029-5515/55/9/092001}, author = {Citrin, J. and Breton, S. and Felici, F. and Imbeaux, F. and Aniel, T. and Artaud, J. F. and Baiocchi, B. and Bourdelle, C. and Camenen, Y. and J. Garcia} } @article {2365, title = {Identification of the ubiquitous Coriolis momentum pinch in JET tokamak plasmas}, journal = {Nuclear Fusion}, volume = {52}, year = {2012}, month = {Apr}, pages = {042001}, type = {Article}, abstract = {A broad survey of the experimental database of neutral beam heated plasmas in the JET tokamak has established the theoretically expected ubiquity, in rotating plasmas, of a convective transport mechanism which has its origin in the vertical particle drift resulting from the Coriolis force. This inward convection, or pinch, leads to inward transport of toroidal angular momentum and is characterized by pinch numbers RV/chi(phi), which rise from near unity at r/a approximate to 0.25 to around 5 at r/a approximate to 0.85. Linear gyrokinetic calculations of the Coriolis pinch number and the Prandtl number chi(phi)/chi(i) are in good agreement with the experimental observations, with similar dependences on plasma parameters. The data, however, do not rule out contributions from different processes, such as residual stresses.}, isbn = {0029-5515}, doi = {10.1088/0029-5515/52/11/114024}, url = {http://iopscience.iop.org/0029-5515/52/11/114024/}, author = {Weisen, H. and Camenen, Y. and Salmi, A. and Versloot, T. W. and de Vries, P. C. and Maslov, M. and Tala, T. and Beurskens, M. and Giroud, C.} } @article {2396, title = {Ubiquity of non-diffusive momentum transport in JET H-modes}, journal = {Nuclear Fusion}, volume = {52}, number = {11}, year = {2012}, pages = {114024}, abstract = {A broad survey of the experimental database of neutral beam heated baseline H-modes and hybrid scenarios in the JET tokamak has established the ubiquity of non-diffusive momentum transport mechanisms in rotating plasmas. As a result of their presence, the normalized angular frequency gradient R \∇ \ω / \ω is higher than expected from momentum diffusion alone, by about unity in the core ( r / a\ \∼\ 0.3), rising to near 5 close to the edge, where its contribution to the total gradient is comparable to the gradient associated with the diffusive flux. The magnitude and parameter dependences of the non-diffusive contribution to the gradient are consistent with a theoretically expected pinch, which has its origin in the vertical particle drift resulting from the Coriolis force. Linear gyrokinetic calculations of the pinch number RV / \χ \φ and the Prandtl number \χ \φ / \χ i are in good agreement with the experimental observations, with similar dependences on R / L n , q and \ε\ =\ r / R . A contribution due to residual stresses may also be present, but could not be identified with certainty.}, doi = {10.1088/0029-5515/52/11/114024}, url = {http://www.iop.org/Jet/article?EFDP11051\&EFDP11055}, author = {Weisen, H. and Camenen, Y. and Salmi, A. and Versloot, T. W. and de Vries, P. C. and Maslov, M. and Tala, T. and Beurskens, M. and Giroud, C. and JET-EFDA Contributors} } @article {2053, title = {Overview of toroidal momentum transport}, journal = {Nuclear Fusion}, volume = {51}, number = {9}, year = {2011}, note = {ISI Document Delivery No.: 818DPTimes Cited: 1Cited Reference Count: 114SI}, month = {Sep}, pages = {094027}, type = {Article}, abstract = {Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related to the breaking of symmetry (parity) along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E x B shearing, particle flux, and up-down asymmetric equilibria) are reasonably well understood. At higher order, expected to be of importance in the plasma edge, the theory is still under development.

}, keywords = {ALCATOR-C-MOD, ANGULAR-MOMENTUM, CYCLOTRON WAVE, FLOWS, INJECTION, ION TEMPERATURE, NEUTRAL-BEAM INJECTION, OFF-LAYER, OHMIC H-MODE, PLASMA ROTATION, RADIAL ELECTRIC-FIELD, TEMPERATURE-GRADIENT MODE}, isbn = {0029-5515}, doi = {10.1088/0029-5515/51/9/094027}, author = {Peeters, A.G. and Angioni, C. and Bortolon, A. and Camenen, Y. and Casson, F. J. and Duval, B. and Fiederspiel, L. and Hornsby, W. A. and Idomura, Y. and Hein, T. and Kluy, N. and Mantica, P. and Parra, F. I. and Snodin, A. P. and Szepesi, G. and Strintzi, D. and Tala, T. and Tardini, G. and P. de Vries and Weiland, J.} }