A reduced model for ion temperature gradient turbulent transport in helical plasmas

Nunami, M.; Watanabe, T.‐H.; Sugama, H.

doi:10.1063/1.4822337

Cited by 46 publications

(81 citation statements)

References 33 publications

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“…In this way, the implementation of ITG-turbulence-induced ion heat diffusivity into numerical modelling, such as TASK3D-a, can be considered as pointed out in Ref. [19].…”

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

“…[19], in which nonlinear gyrokinetic simulation results can be predicted from "less-expensive" linear simulations. The deduced model for ITG-turbulence-induced ion heat diffusivity is represented through the linear ITG growth rates and zonal flow decay times, both of which are available from linear gyrokinetic simulations.…”

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

“…In Ref. [19], 21 nonlinear gyrokinetic simulation results were treated taking the following as parameters: radial position, safety factor, magnetic shear, normalized scale lengths of ion-temperature, and density gradient (cf., Table 1 in Ref. [19]).…”

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

“…A reduced model for the ITG-turbulence-induced ion heat diffusivity has been obtained in Ref. [19] in this regard. In this paper, another trial is introduced; a trial based on the multivariable nonlinear regression analysis, with predictor variables available from the temperature and density profiles and equilibrium.…”

Section: Discussionmentioning

confidence: 99%

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Integration of Large-Scale Simulations and Numerical Modelling Tools in Close Link with the LHD Experiment

Yokoyama

Seki

Suzuki

et al. 2014

Plasma and Fusion Research

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An integrated transport analysis suite, TASK3D-a, has been developed with the emphasis on establishing close-link with the LHD experiment database. The suite makes possible energy transport analyses for huge cases, from which the systematic understandings can be elucidated. A statistical approach for implementing largescale simulation results into the integrated modelling has been tested. The importance of strengthening trilateral links among experiments, large-scale simulations, and integrated numerical modelling tools such as TASK3D, is crucial for promoting systematic understandings, performing validations, and then increasing the predictive capabilities.

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“…In this way, the implementation of ITG-turbulence-induced ion heat diffusivity into numerical modelling, such as TASK3D-a, can be considered as pointed out in Ref. [19].…”

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

Section: Approach For Implementing Largescale Simulation Results Intomentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Integration of Large-Scale Simulations and Numerical Modelling Tools in Close Link with the LHD Experiment

Yokoyama

Seki

Suzuki

et al. 2014

Plasma and Fusion Research

View full text Add to dashboard Cite

show abstract

“…[2][3][4][5][6][7][8]. The gyro-kinetic analysis results in tokamak [9][10][11] and helical [12][13][14] plasmas have been studied with the experimental observations. Gyro-kinetic simulations of helical plasmas require a large number of mesh points along the field line in order to capture the helical ripple structure.…”

mentioning

confidence: 99%

A Reduced Transport Model for Ion Heat Diffusivity by Gyro-Kinetic Analysis with Kinetic Electrons in Helical Plasmas

Toda

Nakata

Nunami

et al. 2017

Plasma and Fusion Research

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A high ion temperature plasma in the Large Helical Device is examined in the case in which the ion temperature gradient mode is unstable. The nonlinear gyro-kinetic simulation is performed to evaluate the turbulent ion heat diffusivity with the kinetic electron response. It is clarified that the decay time of zonal flows [S. FerrandoMargalet et al., Phys. Plasmas 14, 122505 (2007)] decreases radially outward due to the trapped electron and the ion energy transport increases outward. To reduce the computational cost for applying to the dynamical transport simulation, an extended transport model for the ion heat diffusivity in terms of the mixing length estimate and the characteristic quantity for the linear response of zonal flows is proposed. Turbulent transport is one of the most critical issues for plasma confinement in magnetic fusion devices. Theoretical expressions for the turbulent transport due to the various instabilities were reviewed [1]. Recently, a large number of the gyro-kinetic simulations which are applied to the turbulent transport have been performed in toroidal plasmas, e.g. [2][3][4][5][6][7][8]. The gyro-kinetic analysis results in tokamak [9][10][11] and helical [12][13][14] plasmas have been studied with the experimental observations. Gyro-kinetic simulations of helical plasmas require a large number of mesh points along the field line in order to capture the helical ripple structure. Therefore, the gyro-kinetic analysis in helical plasmas consumes the larger computer resources than for tokamaks. In helical plasmas, it is not practical to perform the nonlinear gyro-kinetic simulation at each time step of the dynamical transport code. The reduced model, which reproduces the nonlinear gyro-kinetic analysis results, is needed for the dynamical transport simulation in helical plasmas.The GKV code [15] has been used to examine the ion temperature gradient (ITG) mode and zonal flows in the Large Helical Device (LHD) for studying the turbulent transport [13]. The gyro-kinetic simulation with the adiabatic electron is performed for the high ion temperature LHD discharge (shot number 88343 [16]). The ion energy flux by the ITG mode instability agrees with the experimental results [13,14]. The reduced model for the ion heat diffusivity is proposed [14] by the simulation with the adiabatic electron. This reduced model is the function of the author's e-mail: toda@nifs.ac.jp linear growth rate for the ITG mode and the zonal flow decay time [17,18]. In tokamak plasmas, the gyro-kinetic analysis at each time step is globally performed in the dynamical transport simulation [19,20]. How to apply the reduced model of the turbulent ion heat diffusivity from the gyro-kinetic simulation with the adiabatic electron to the transport code has been shown in helical plasmas [21]. The simulation with the kinetic electron shows the larger ion energy flux than the experimental results in the high-T i LHD discharge [22]. On the other hand, the electron and ion energy fluxes of the simulation results with the kinetic el...

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Modification of a machine learning‐based semi‐empirical turbulent transport model for its versatility

Narita

Honda

Nakata

et al. 2023

Contributions to Plasma Physics

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A machine learning‐based semi‐empirical turbulent transport model DeKANIS has been modified to apply it independently of the device. DeKANIS predicts particle and heat fluxes, distinguishing diffusive and non‐diffusive transport processes. DeKANIS consists of a neural network (NN) model, which computes coefficients of the non‐diffusive terms and the ratio of the fluxes based on the gyrokinetic calculations, and a scaling formula, which estimates the turbulent saturation level founded on empirical fluxes. The datasets used for NN training have been prepared based on JT‐60U plasmas so far, but by exploiting JET plasmas, the datasets have been expanded and the parameter ranges covered by the NN models have become wider. The scaling formula has been rebuilt considering the decrease in the residual zonal flow level due to collisions. The new DeKANIS has demonstrated a reasonable profile prediction of an ITER plasma in the pre‐fusion power operation 1 phase with an integrated model GOTRESS+. In validating the prediction results with the gyrokinetic calculations, transport processes causing the fluxes have been exhibited.

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A reduced model for ion temperature gradient turbulent transport in helical plasmas

Cited by 46 publications

References 33 publications

Integration of Large-Scale Simulations and Numerical Modelling Tools in Close Link with the LHD Experiment

Integration of Large-Scale Simulations and Numerical Modelling Tools in Close Link with the LHD Experiment

A Reduced Transport Model for Ion Heat Diffusivity by Gyro-Kinetic Analysis with Kinetic Electrons in Helical Plasmas

Modification of a machine learning‐based semi‐empirical turbulent transport model for its versatility

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