Impact of Magnetic Field Configuration on Heat Transport in Stellarators and Heliotrons

Warmer, F.; Tanaka, K.; Xanthopoulos, P.; Nunami, M.; Nakata, M.; Beidler, C. D.; Bozhenkov, S.; Beurskens, M.; Brunner, K. J.; Ford, O.; Fuchert, G.; Funaba, H.; Geiger, J.; Gradic, D.; Ida, K.; Igami, H.; Kubo, S.; Langenberg, A.; Laqua, H. P.; Lazerson, S.; Morisaki, T.; Osakabe, M.; Pablant, N.; Pasch, E.; Peterson, B.J.; Satake, S.; Seki, R.; Shimozuma, Τ.; Smith, H. M.; Stange, T.; Stechow, A. von; Sugama, H.; Suzuki, Yasuhiro; Takahashi, H.; Tokuzawa, T.; Tsujimura, Toru Ii; Turkin, Y.; Wolf, R. C.; Yamada, I.; Yanai, Ryoma; Yasuhara, Ryo; Yokoyama, M.; Yoshimura, Y.; Yoshinuma, M.; Zhang, D; Team, W X; Group, LHD Experimental

doi:10.1103/physrevlett.127.225001

Cited by 15 publications

(13 citation statements)

References 47 publications

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“…The LHD heliotron has the highest critical gradient of all cases considered, as a result of significant drift curvature a/R eff 0.45. Interestingly, its highly favorable comparison with W7-X (a factor of ∼ 7 greater) is in line with the difference in nonlinear heat fluxes obtained via gyrokinetic simulations [39].…”

supporting

confidence: 77%

Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators

Roberg-Clark

Plunk

Xanthopoulos

2022

Phys. Rev. Research

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We present a modified gyrokinetic theory to predict the critical gradient that determines the linear onset of the ion temperature gradient (ITG) mode in stellarator plasmas. A coarse-graining technique is applied to the drift curvature, entering the standard gyrokinetic equations, around local minima. Thanks to its simplicity, this novel formalism yields an estimate for the critical gradient with a computational cost low enough for application to stellarator optimization. On comparing against a gyrokinetic solver, our results show good agreement for an assortment of stellarator designs. Insight gained here into the physics of the onset of the ITG driven instability enables us to devise a compact configuration, similar to the Wendelstein 7-X device, but with almost twice the ITG linear critical gradient, an improved nonlinear critical gradient, and reduced ITG mode transport above the nonlinear critical gradient.

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supporting

confidence: 77%

Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators

Roberg-Clark

Plunk

Xanthopoulos

2022

Phys. Rev. Research

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“…The spatial resolution of turbulence profile is approximately 20%. LHD絶対値計測 152264 t = 4.47 Recently, a study comparing the transport in LHD and the Wendelstein 7-X (W7-X) was conducted [19]. At comparable electron density (𝑛 𝑒 = 1.5 × 10 19 m −3 ), the neoclassical ion-heat transport of W7-X is reported to be lower than that of LHD, and the anomalous ion-heat transport of LHD is lower than that of W7-X, resulting in comparable total heat transport [19].…”

Section: Two-dimensional Phase Contrast Imagingmentioning

confidence: 99%

“…LHD絶対値計測 152264 t = 4.47 Recently, a study comparing the transport in LHD and the Wendelstein 7-X (W7-X) was conducted [19]. At comparable electron density (𝑛 𝑒 = 1.5 × 10 19 m −3 ), the neoclassical ion-heat transport of W7-X is reported to be lower than that of LHD, and the anomalous ion-heat transport of LHD is lower than that of W7-X, resulting in comparable total heat transport [19]. Furthermore, the anomalous ion-heat flux is almost consistent with the ionheat flux calculated by nonlinear gyrokinetic simulations (GKV [20] for LHD and GENE [21] for W7-X).…”

Section: Two-dimensional Phase Contrast Imagingmentioning

confidence: 99%

Absolute value measurement of ion-scale turbulence by two-dimensional phase contrast imaging in Large Helical Device

Kinoshita,

Tanaka,

Sakai

et al. 2023

J. Inst.

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Absolute value measurements of turbulence amplitude in magnetically confined high-temperature plasmas can effectively explain turbulence-driven transport characteristics and their role in plasma confinements. Two-dimensional phase contrast imaging (2D-PCI) is a technique to evaluate the space-time spectrum of ion-scale electron density fluctuation. However, absolute value measurement of turbulence amplitude has not been conducted owing to the nonlinearity of the detector. In this study, the absolute measurement method proposed in the previous study is applied to turbulence measurement results in the large helical device. As a result, the localized turbulence amplitude at ne = 1.5 × 1019 m-3 is approximately 3.5 × 1015 m-3, which is 0.02% of the electron density. In addition, the evaluated poloidal wavenumber spectrum is almost consistent, within a certain error range, the spectrum being calculated using a nonlinear gyrokinetic simulation. This result is the first to the best of our knowledge to quantitatively evaluate turbulence amplitudes measured by 2D-PCI and compare with simulations.

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“…In magnetic confined fusion plasma researches, firstprinciple simulation based on gyrokinetic model 1 is a powerful and reliable means to predict the turbulent transport or profiles of plasma temperatures and densities. Indeed, it has been possible to validate local gyrokinetic simulations against experimental observations of transport fluxes within experimental errors [2][3][4][5] . For the predictions, there are two main approaches.…”

Section: Introductionmentioning

confidence: 99%

Improved prediction scheme for ion heat turbulent transport

et al. 2022

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A novel scheme to predict the turbulent transport of ion heat of magnetic confined plasmas is developed by combining mathematical optimization techniques employed in data analysis approaches and first-principle gyrokinetic simulations. Gyrokinetic simulation, as a first-principle approach, is a reliable way to predict turbulent transport. However, in terms of the flux-matching [Candy et al., Phys. Plasmas 16, 060704 (2009)], quantitative transport estimates by gyrokinetic simulations incur extremely heavy computational costs. In order to reduce the costs of quantitative transport prediction based on the gyrokinetic simulations, we develop a scheme with the aid of a reduced transport model. In the scheme, optimization techniques are applied to find relevant input parameters for nonlinear gyrokinetic simulations, which should be performed to obtain relevant transport fluxes and to optimize the reduced transport model for a target plasma. The developed scheme can reduce the numbers of the gyrokinetic simulations to perform the quantitative estimate of the turbulent transport levels and plasma profiles. Utilizing the scheme, the predictions for the turbulent transport can be realized by performing the first-principle simulations once for each radial position.

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Impact of Magnetic Field Configuration on Heat Transport in Stellarators and Heliotrons

Cited by 15 publications

References 47 publications

Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators

Coarse-grained gyrokinetics for the critical ion temperature gradient in stellarators

Absolute value measurement of ion-scale turbulence by two-dimensional phase contrast imaging in Large Helical Device

Improved prediction scheme for ion heat turbulent transport

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