Validation study of GENE on ASDEX Upgrade using perturbative thermal diffusivity measured with partial sawtooth heat pulses

Creely, A. J.; Görler, T.; Freethy, S. J.; Howard, Nathan; Schneider, P. A.; White, Anne; Willensdorfer, M.

doi:10.1088/1741-4326/aadca1

Cited by 6 publications

(6 citation statements)

References 46 publications

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“…This is supported by extensive verification and validation work, e.g. in [15][16][17][18][19][20][21][22] regarding heat transport, which is the main focus of this paper, but also regarding main particle, impurity and momentum transport (see e.g. [23][24][25][26][27][28]).…”

Section: Non-linear Gyrokinetic and Reduced Modelsmentioning

confidence: 74%

Progress and challenges in understanding core transport in tokamaks in support to ITER operations

Mantica

Angioni

Bonanomi

et al. 2019

Plasma Phys. Control. Fusion

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Fusion performance in tokamaks depends on the core and edge regions as well as on their nonlinear feedbacks. The achievable degree of edge confinement under the constraints of power handling in presence of a metallic wall is still an open question. Therefore, any improvement in the core temperature and density peaking is crucial for achieving target performance. This has motivated further progress in understanding core turbulent transport mechanisms, to help scenario development in present devices and improve predictive tools for ITER operations. In the last two decades, detailed experiments and their interpretation via the gyrokinetic theory of turbulent transport have led to a satisfactory level of understanding of the heat, particle, and momentum transport channels and of their mutual interactions. This paper presents some highlights of the progress, which stems from joint work of several devices and theory groups, in Europe and worldwide within the ITPA (International Tokamak Physics Activities) framework. On the other hand, the achievement of predictive capabilities of plasma profiles via integrated modeling, which also accounts for the nonlinear interactions inherent to the multi-channel nature of transport, is a priority in view of ITER. This requires using faster, reduced models, and the extent to which they capture the complex physics described by nonlinear gyrokinetics must be carefully evaluated. Present quasi-linear models match well experiments in baseline scenarios, and thus offer reliable predictions for the ITER reference scenario, but have issues in advanced scenarios. Some of these challenges are examined and discussed. In the longer term, advances in high performance computing will continue to drive physics discovery through increasingly complex gyrokinetic simulations, allowing also further development of reduced models. The development of neural network surrogate models is another recent advance that bridges the gap towards physics-based fast models for optimisation and control applications.

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Section: Non-linear Gyrokinetic and Reduced Modelsmentioning

confidence: 74%

Progress and challenges in understanding core transport in tokamaks in support to ITER operations

Mantica

Angioni

Bonanomi

et al. 2019

Plasma Phys. Control. Fusion

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“…This quantification was used to develop criteria with which one is able to determine whether or not multi-scale effects will be important in a plasma discharge, without performing nonlinear simulations. These criteria are based on properties of the linear growth rates of the plasmas, similar to some past work, which suggested that g g -k k high low might be one such criterion [13,16,19]. In this criterion, g -k high is the 5 To address a possible confusion, note that c Ricci is not a diffusivity (unlike c e pert ) and is unitless.…”

Section: Riccimentioning

confidence: 94%

“…The perturbative diffusivity therefore measures the extent to which a change in the electron temperature gradient changes the electron heat flux. This study uses the propagation of partial sawtooth generated heat pulses in order to measure the perturbative diffusivity [18,19]. In particular, the Extended-Time-to-Peak calculation method [42] is used on heat pulses generated by partial sawteeth, as these avoid complications associated with full sawteeth [43].…”

Section: Machines and Experimental Measurementsmentioning

confidence: 99%

“…(2) Ion-scale simulations match heat fluxes, but miss other constraints, while multi-scale simulations match everything [16]. (3) Ion-scale simulations simultaneously match heat fluxes and other constraints, indicating that multiscale effects are unimportant [19]. The intent of this article is to outline a set of criteria that differentiates these cases, and in doing so probe the underlying physical phenomena that govern multi-scale turbulent interactions.…”

Section: Introductionmentioning

confidence: 99%

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Criteria for the importance of multi-scale interactions in turbulent transport simulations

Creely

Rodriguez-Fernandez

Freethy

et al. 2019

Plasma Phys. Control. Fusion

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Turbulent transport simulations have been used to develop criteria that indicate when multi-scale turbulent phenomena are important in tokamak plasmas. Twelve experimental plasma discharges from the Alcator C-Mod and ASDEX Upgrade tokamaks are compared to ion-and multi-scale simulations with the Trapped Gyro-Landau Fluid (TGLF) turbulence code. Multi-scale TGLF agrees with all available validation constraints (ion heat flux, electron heat flux, electron temperature fluctuations, and electron perturbative thermal diffusivity) within uncertainty for all cases analyzed. Ion-scale TGLF agrees in only some cases. Two criteria based on the ratios of normalized linear growth rates are able to distinguish cases in which ion-scale simulations are sufficient from cases for which multi-scale simulations are necessary. The form of these criteria reveal the key role of zonal flow mixing in moderating multi-scale effects.

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“…Both models predict a continuous spectrum of electron modes are unstable above k y ρ s = 1, which smoothly transition from a TEM mode at k y ρ s ∼ 1 to the ETG mode by k y ρ e ∼ 0.5-1 (k y ρ s ∼ 30-60). However, both models also predict that these electron modes have growth rates which are still sufficiently small that they are not expected to contribute significantly to transport, based on published criteria [53]. Because of the focus on ion thermal transport in this work, and computational expense of nonlinear multiscale simulations which would self-consistently include both ITG and ETG dynamics, these short-wavelength modes are not considered further in this paper.…”

Section: Comparisons Of Tglf and Cgyro Linear Growth Ratesmentioning

confidence: 99%

Examination of stiff ion temperature gradient mode physics in simulations of DIII-D H-mode transport

et al. 2021

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A systematic evaluation of gyrokinetic and gyrofluid model predictions of ion temperature gradient (ITG) stability and transport using parameters from DIII-D high confinement mode (H-mode) plasmas has been performed. The nonlinear CGYRO code is used to make the gyrokinetic predictions, and the quasilinear TGLF model for the corresponding gyrofluid predictions. The assessments are made at three radii (normalized toroidal flux ρ tor = 0.4, 0.55, and 0.7) in three different plasma scenarios with varying levels of neutral beam heating and torque. For each of the nine cases (3 radii × 3 scenarios) considered, ITG turbulence is found to be the dominant long-wavelength instability and transport mechanism. The inclusions of both transverse magnetic fluctuations and dynamic fast beam ions are stabilizing for all cases considered, with strongest effects seen at ρ or = 0.4 where the fast ion population and normalized plasma pressure β = 2μ 0 nT/B 2 are highest. The further inclusion of parallel magnetic fluctuations does not have a meaningful impact on the ITG turbulence in these scenarios, but does destabilize (in combination with fast ions) new high-frequency instabilities at ρ tor = 0.4 in the high power scenarios. In each case the linear and nonlinear ITG critical gradients are predicted to be lower than the measured ITG scale lengths and their associated uncertainties. Inclusion of equilibrium flow shear in the transport predictions generally leads to an upshift in effective critical gradient rather than a qualitative change in the predicted stiffness, with stronger responses typically seen in the gyrokinetic predictions than in the gyrofluid results. However, in most cases these upshifted gradients still remain below the measured values and their uncertainties. Although the predicted critical gradients are below the measured gradients, both models predicted flux-matching gradients consistent with measured values in six of the nine cases considered, with no clear systematic over- or underprediction. Thus, while the experimental ion temperature profiles do not appear to be closely pinned to the ITG critical gradient, both gyrokinetic and gyrofluid models are able to accurately match the measured gradients reasonably well in most cases.

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Validation study of GENE on ASDEX Upgrade using perturbative thermal diffusivity measured with partial sawtooth heat pulses

Cited by 6 publications

References 46 publications

Progress and challenges in understanding core transport in tokamaks in support to ITER operations

Progress and challenges in understanding core transport in tokamaks in support to ITER operations

Criteria for the importance of multi-scale interactions in turbulent transport simulations

Examination of stiff ion temperature gradient mode physics in simulations of DIII-D H-mode transport

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