Recent developments in engineering design for the quasi-axisymmetric stellarator CFQS

Shimizu, A.; Kinoshita, Shigeyoshi; Isobe, M.; Okamura, S.; Ogawa, K.; Nakata, M.; Yoshimura, Y.; Suzuki, C.; Osakabe, M.; Murase, Takuhei; Nakagawa, Setsuko; Tanoue, Hironobu; Xu, Yuhong; Liu, Haifeng; Liu, Hai; Huang, Jie; Wang, Xianqu; Cheng, J.; Xiong, Guozhen; Tang, C. J.; Yin, Di; Wang, Y

doi:10.1088/1741-4326/ac369a

Cited by 8 publications

(10 citation statements)

References 35 publications

(51 reference statements)

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“…1(b). The method described above, in accordance with the electrostatic limit of gyrokinetics, is applied to vacuum flux-tube geometries generated for an assortment of stellarator designs, including HSX [29], CFQS [30], NCSX [31], LHD [32], QPS [33], the high-mirror configuration of Wendelstein 7-X [34], a quasi-axisymmetric stellarator NAS [35], and a modified high-mirror W7-X (KJM) case that we call W7-K, described in the next section. In Fig.…”

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confidence: 99%

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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confidence: 99%

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

Roberg-Clark

Plunk

Xanthopoulos

2022

Phys. Rev. Research

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“…Moreover, the effects of the bootstrap current on neoclassical transport were investigated and a satisfactory neoclassical transport maintained up to β = 1.5% [11]. Now the fabrication of the CFQS device is steadily progressing to achieve its first plasma [12]. It is noted in previous work [9][10][11][12], that the bootstrap current was estimated with the BOOTSJ code, which uses a semi-analytic formula in the collision-less limit [13].…”

Section: Introductionmentioning

confidence: 99%

“…Now the fabrication of the CFQS device is steadily progressing to achieve its first plasma [12]. It is noted in previous work [9][10][11][12], that the bootstrap current was estimated with the BOOTSJ code, which uses a semi-analytic formula in the collision-less limit [13]. The bootstrap current density predicted with this code is usually noisy or has 'spikes' near the rational surfaces [10,14], which results from the shortcoming of the low-collisionality bootstrap analytical formula.…”

Section: Introductionmentioning

confidence: 99%

Effects of bootstrap current on magnetic configuration in Chinese first quasi-axisymmetric stellarator

Liu

zhang

et al. 2023

Nucl. Fusion

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Neoclassical properties in quasi-axisymmetric (QA) stellarators are analogous to these in tokamaks. Consequently, a substantial bootstrap current could significantly modify the MHD equilibrium properties of a QA stellarator, which is an important characteristic in this type of stellarator. This paper is dedicated to systemically investigate the effects of bootstrap current on the magnetic configuration in Chinese First Quasi-axisymmetric Stellarator (CFQS). For the first time, self-consistent bootstrap currents in free-boundary equilibria are calculated with an accurate Fokker–Planck neoclassical numerical mode in CFQS. Several important results are achieved: 1) As the bootstrap current grows with increasing volume-averaged normalized pressure β, the magnetic shear develops in the bulk plasma and meanwhile, a deep magnetic well is robustly sustained, which leads to improved stabilization of interchange modes up to β~2.0%. 2) In the analysis of global ideal MHD instability, as the bootstrap current rises to 39kA (β~1.3%), external kink modes become destabilized and the unstable mode with m/n= 2/1 is dominant. 3) From β=0 to 1.5%, the bootstrap current hardly changes the quasi-axisymmetric property and a low neoclassical transport is maintained. However, as β is enhanced beyond 2.0%, the substantial bootstrap current gives rise to an increase of non-quasi-axisymmetric magnetic field components, which weakens the neoclassical transport properties. 4) An increase of the negative magnetic shear at the core region by the bootstrap currents has a favorable effect on the properties of J (second adiabatic invariant). The maximum-J region can be extended by raising bootstrap currents.

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“…A quasi-axisymmetric stellarator, CFQS, has now been constructed as a joint project between National Institute for Fusion Science and Southwest Jiaotong University [1]. The CFQS is a low-aspect-ratio stellarator based on CHS-qa [2].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Magnetic Field Configuration for Magnetic Surface Measurements in the CFQS Quasi-Axisymmetric Stellarator

Shoji

Akihiro

Kinoshita

et al. 2023

Plasma and Fusion Research

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It has been found that magnetic surfaces in the CFQS quasi-axisymmetric stellarator in a standard magnetic configuration are robust against error fields caused by misalignments of the modular coils. While this property is advantageous for preserving the magnetic field line structures for the plasma confinement as designed, it prevents the detection of the misalignments of the coils by magnetic surface measurements. Thus, a magnetic configuration specialized in measuring magnetic surfaces to detect the error fields is proposed. Calculations by tracing magnetic field lines reveal that the magnetic surfaces in the specialized magnetic configuration are sensitive to the error fields compared to those in the standard magnetic configuration. Additionally, the calculations demonstrate that a weighted electric current on some modular coils can make the magnetic surfaces more sensitive to the error fields, which enables the magnetic surface measurements to detect smaller misalignments of the modular coils in the CFQS.

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Recent developments in engineering design for the quasi-axisymmetric stellarator CFQS

Cited by 8 publications

References 35 publications

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

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

Effects of bootstrap current on magnetic configuration in Chinese first quasi-axisymmetric stellarator

Investigation of the Magnetic Field Configuration for Magnetic Surface Measurements in the CFQS Quasi-Axisymmetric Stellarator

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