Simulations of divertor particle and heat loads in ohmic and L-mode plasmas in DIII-D, AUG, and JET using UEDGE Simulations of divertor particle and heat loads in ohmic and L-mode plasmas in DIII-D, AUG, and JET using UEDGE and the DIII-D and ASDEX Upgrad

Abstract (134 words) Measurements and simulations with the UEDGE code of radiated power, and ion saturation currents and power loads to the target plates have been compared for density scans in ohmic and low confinement mode plasmas in DIII-D, ASDEX Upgrade, and JET. Overall, a significantly better match has been obtained when cross-field drifts are used and elevated chemical sputtering yields of 3-4% are assumed. Using these assumptions the simulations DRAFT 3 2 reproduce the measured currents and powers, and their functional dependence on upstream density to within a factor of 2, with the exception of the ion currents to the low field side target in ASDEX Upgrade and the high field side target in JET. The applicability of using enhanced sputtering yields is discussed by comparing measured and simulated emission from low charge state carbon in the divertor regions

Turbulence stabilization due to high beta and fast ions in high-performance plasmas at ASDEX Upgrade and JET

High-performance fusion plasmas are desired to reach high plasma beta. Yet, the dependence of the thermal confinement time on this important parameter is unclear: Dedicated experiments yielded inconclusive results [1] and most theoretical results are obtained in simplified setups (overview e.g. in Ref. [2]). Using high accuracy plasma parameter measurements and realistic geometry for recent H-mode discharges at ASDEX Upgrade and JET (with ITER-like-wall), turbulent transport is studied by means of GENE gyrokinetic simulations in the plasma core. Electromagnetic effects in plasma microturbulence The gyrokinetic simulation code GENE is developed for studying microturbulence in strongly magnetized plasmas, such as fusion plasmas. In this work, we use the local flux-tube version of GENE A pair of ASDEX Upgrade discharges varying β In the ASDEX Upgrade discharges #29197 (case A, β N = 1.67) and #29224 (case B, β N = 2.6), β e varies by a factor of two at mid-radius, while changes in other dimensionless parameters, such as ρ ⋆ and ν ⋆ , as well as magnetic geometry are by far less pronounced 42 nd EPS Conference on Plasma Physics P1.15

NBI Modulation Experiments to Study Momentum Transport and Magnetic Field Induced Ripple Torque on JET

Abstract. Several parametric scans have been performed to study momentum transport on JET. NBI modulation technique has been applied to separating the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density gradient length, with an experimental scaling for the pinch number being -Rv pinch = 1.2R/L n + 1.4. There is no dependence of the pinch number on collisionality. The Prandtl number was not found to depend either on R/L n , collisionality or on q. The gyrokinetic simulations show qualitatively similar dependence of the pinch number on R/L n , but the dependence is weaker in the simulations. Gyro-kinetic simulations do not find any clear parametric dependence in the Prandtl number, in agreement with experiments, but the experimental values are larger than the simulated ones. The extrapolation of these results to ITER illustrates that at R/L n >2 the pinch number becomes large enough (> 3 4) to make the rotation profile peaked provided that the edge rotation is non-zero. And this rotation peaking can be achieved with small or even with no core torque source. The absolute value of the core rotation is still very challenging to predict partly due to the lack of the present knowledge of the rotation at the plasma edge, partly due to insufficient understanding of 3D effects like braking and partly due to the uncertainties in the extrapolation of the present momentum transport results to a larger device

NBI Modulation Experiments to Study Momentum Transport and Magnetic Field Induced Ripple Torque on JET NBI Modulation Experiments to Study Momentum Transport and Magnetic Field Induced Ripple Torque on JET

AbstrAct Several parametric scans have been performed to study momentum transport on JET. NBI modulation technique has been applied to separating the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density gradient length, with an experimental scaling for the pinch number being -Rv pinch / χφ = 1.2R/L n + 1.4. There is no dependence of the pinch number on collisionality. The Prandtl number was not found to depend either on R/L n , collisionality or on q. The gyro-kinetic simulations show qualitatively similar dependence of the pinch number on R/L n , but the dependence is weaker in the simulations. Gyrokinetic simulations do not find any clear parametric dependence in the Prandtl number, in agreement with experiments, but the experimental values are larger than the simulated ones. The extrapolation of these results to ITER illustrates that at R/L n >2 the pinch number becomes large enough (> 3−4) to make the rotation profile peaked provided that the edge rotation is non-zero. And this rotation peaking can be achieved with small or even with no core torque source. The absolute value of the core rotation is still very challenging to predict partly due to the lack of the present knowledge of the rotation at the plasma edge, partly due to insufficient understanding of 3D effects like braking and partly due to the uncertainties in the extrapolation of the present momentum transport results to a larger device

TH/P3-45 Integrated Core-SOL-Divertor Modelling for ITER Including Impurity: Effect of Tungsten on Fusion Performance in H-mode and Hybrid Scenario

Abstract. The compatibility of two operational constraints -operation above the L-H power threshold and at low power to divertor -is examined for ITER long pulse H-mode and hybrid scenarios in integrated core-SOLdivertor modelling including impurities (intrinsic Be, He, W and seeded Ne). The core thermal, particle and momentum transport is simulated with the GLF23 transport model tested in the self-consistent simulations of temperatures, density and toroidal rotation velocity in JET hybrid discharges and extrapolated to ITER. The beneficial effect of toroidal rotation velocity on fusion gain is shown. The sensitivity studies with respect to operational (separatrix and pedestal density, Ne gas puff) and unknown physics (W convective velocity and perpendicular diffusion in SOL as well as W prompt re-deposition) parameters are performed to determine their influence on the operational window and fusion gain

Modelling of Hybrid Scenario: from present-day experiments toward ITER , ASDEX-Upgrade Team, JET-EFDA contributors * , and the EU-ITM ITER Scenario Modelling group

Abstract. The 'hybrid' scenario is an attractive operating scenario for ITER since it combines long plasma duration with the reliability of the reference H-mode regime. We review the recent European modelling effort carried out within the Integrated Scenario Modelling group which aims at (i) understanding the underlying physics of the hybrid regime in ASDEX-Upgrade and JET, and, (ii) extrapolating them toward ITER. JET and ASDEX-Upgrade hybrid scenarios performed under different experimental conditions have been simulated in an interpretative and predictive way in order to address the current profile dynamics and its link with core confinement, the relative importance of magnetic shear, s, and ExB flow shear on the core turbulence, pedestal stability and H-L transition. The correlation of the improved confinement with an increased s/q at outer radii observed in JET and ASDEX-Upgrade discharges is consistent with the predictions based on the GLF23 model applied in the simulations of the ion and electron kinetic profiles. Projections to ITER hybrid scenarios have been carried out focusing on optimization of the heating/current drive schemes to reach and ultimately control the desired plasma equilibrium using ITER actuators. Firstly, access condition to the hybrid-like q-profiles during the current ramp-up phase has been investigated. Secondly, from the interpreted role of the s/q ratio, ITER hybrid scenario flat-top performance has been optimized through tailoring the q-profile shape and pedestal conditions. EPED predictions of pedestal pressure and width have been used as constraints in the interpretative modelling while the core heat transport is predicted by GLF23. Finally, model based approach for real-time control of advanced tokamak scenarios has been applied to ITER hybrid regime for simultaneous magnetic and kinetic profile control