Global gyrokinetic simulations of ASDEX Upgrade up to the transport timescale with GENE–Tango

Abstract

An accurate description of turbulence up to the transport time scale is essential for predicting core plasma profiles and enabling reliable calculations for designing advanced scenarios and future devices. Here, we exploit the gap separation between turbulence and transport time scales and couple the global gyrokinetic code GENE to the transport-solver Tango, including kinetic electrons, collisions, realistic geometries, toroidal rotation and electromagnetic effects for the first time. This approach overcomes gyrokinetic codes' limitations and enables high-fidelity profile calculations in experimentally relevant plasma conditions, significantly reducing the computational cost. We present numerical results of GENE-Tango for two ASDEX Upgrade discharges, one of which exhibits a pronounced peaking of the ion temperature profile not reproduced by TGLF-ASTRA. We show that GENE-Tango can correctly capture the ion temperature peaking observed in the experiment. By retaining different physical effects in the GENE simulations, e.g., collisions, toroidal rotation and electromagnetic effects, we demonstrate that the ion temperature profile's peaking is due to electromagnetic effects of submarginal (stable) KBM modes. Based on these results, the expected GENE-Tango speedup for the ITER standard scenario is larger than two orders of magnitude compared to a single gyrokinetic simulation up to the transport time scale, possibly making first-principles ITER simulations feasible on current computing resources.

Predictions of improved confinement in SPARC via energetic particle turbulence stabilization

“…A quantitative analysis would require gyrokinetic simulations allowing the plasma profiles to self-consistently evolve due to the combined effect of turbulence and external particle and heat sources. These analyses will be performed in the near future, exploiting the recent GENE-Tango code coupling [21].…”

“…Substantial speedups have been reported in the literature with such code coupling, enabling profile predictions with gyrokinetic codes. This (or similar approaches) is done both with flux-tube [7,35] and radially global gyrokinetic codes [21].…”

“…Based on predictive TRANSP simulations with EPED-TGLF, the here considered off-axis ICRF heating scenario is predicted to reach a fusion gain of Q ∼ 0.9. In the following, we will present dedicated local and radially global gyrokinetic GENE [15,16] simulations demonstrating that energetic particle effects-only partially captured by TGLF [17][18][19][20][21] when run with unusual high resolution [22])-strongly suppress turbulent transport in a narrow core region and ultimately trigger a transport barrier.…”

Maximizing the ion temperature in an electron heated plasma: from WEST towards larger devices

“…QuaLiKiz, hence its neural network regression, captures these effects. Regarding the problem of ion temperature saturation, it was found that the T e /T i dependence of turbulent transport was exacerbating this saturation [31]. It is therefore essential to explore the impact of larger T e /T i on turbulent transport and quantify its impact against collisional equipartition in explaining the T i saturation.…”

An IMAS-integrated workflow for energetic particle stability

“…Non-linear (gyro-) fluid models [7] can cover longer timescales, but besides the lack of kinetic effects, the deep non-linear evolution poses still some unresolved challenges. Also, direct coupling schemes of high-fidelity simulations and transport codes are presently developed [8], which however are also extremely costly. Therefore, robust reduced models for the analysis of stability and transport are needed as an additional tool.…”