The three-dimensional equilibrium with magnetic islands and MHD instabilities in the CFQS quasi-axisymmetric stellarator

Wang, Xianqu; Xu, Yuhong; Shimizu, A.; Isobe, M.; Okamura, S.; Todo, Y.; Wang, H.; Liu, H.; Huang, Jie; Zhang, X.; Liu, Hai; Cheng, J.; Tang, C. J.

doi:10.1088/1741-4326/abd3ec

Cited by 13 publications

(20 citation statements)

References 28 publications

(42 reference statements)

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“…Many studies based on the CFQS have already been carried out and they cover different topics like configuration optimization, MHD instabilities, energetic particle driven instabilities, etc. [6][7][8] Energetic particle driven instability is an important issue for fusion research. During energetic particle driven instabilities, the radial transport of energetic particles will be enhanced and a lot of energetic particles lost, and thus heating performance will deteriorate, and the confinement level will decrease.…”

Section: Simulations Of Energetic Particle Driven Instabilities In Cf...mentioning

confidence: 99%

Simulations of energetic particle driven instabilities in CFQS

Wang¹,

Todo²,

Huang³

et al. 2022

Nucl. Fusion

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A nonlinear simulation of the energetic particle driven instabilities in the Chinese First Quasi-Axisymmetric Stellarator (CFQS) has been conducted for the first time. MEGA, a hybrid simulation code for energetic particles interacting with a magneto-hydrodynamic (MHD) fluid, was used in the present work. Both the m/n=3/1 energetic-particle-mode (EPM) like mode and the m/n=5/2 toroidal Alfvén eigenmode (TAE) were found, where m is the poloidal mode number and n is the toroidal mode number. Four important results were obtained as follows. First, the instability in the CFQS in three-dimensional form was shown for the first time. Second, strong toroidal mode coupling was found for the spatial profiles, and it is consistent with the theoretical prediction. Third, the resonant condition caused by the absence of axial symmetry in CFQS was demonstrated for the first time. The general resonant condition is fmode=Nfφ-Lfθ, where fmode, fφ, and fθ are mode frequency, particle toroidal transit frequency, and particle poloidal transit frequency, respectively; N and L are arbitrary integers, represent toroidal and poloidal resonance numbers. For EPM-like mode, the dominant and subdominant resonant conditions are fmode=3fφ-7fθ and fmode=fφ-fθ, respectively. For TAE, the dominant and subdominant resonant conditions are fmode=4fφ-9fθ and fmode=2fφ-3fθ, respectively. On the one hand, the toroidal resonance numbers are different from the toroidal mode numbers by 2. This indicates that the 2-fold rotational symmetry affects the resonance condition. On the other hand, the subdominant resonances satisfy N=n, which is expected for the axisymmetric plasmas and most of the toroidal plasmas including stellarators. Fourth, the nonlinear frequency chirpings in CFQS were demonstrated for the first time. Hole and clump structures were formed in the pitch angle and energy phase space, and the particles comprising the hole and clump were kept resonant with the modes during the mode frequencies chirping.

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Section: Simulations Of Energetic Particle Driven Instabilities In Cf...mentioning

confidence: 99%

Simulations of energetic particle driven instabilities in CFQS

Wang¹,

Todo²,

Huang³

et al. 2022

Nucl. Fusion

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“…For density, n0 = 1.0  10 19 m -3 , and Ti = 0.75 Te are assumed. The finite beta MHD equilibrium is calculated by HINT2 [20,21] as shown in Fig. 3.…”

Section: Physics Property Of the Cfqsmentioning

confidence: 99%

“…For the density, n 0 = 1.0 × 10 19 m −3 , and T i = 0.75T e are assumed. The finite beta MHD equilibrium is calculated by HINT2 [20,21], as shown in figure 3. Poincare plots of the magnetic field line at the toroidal angle of 0 deg.…”

Section: Physics Properties Of the Cfqsmentioning

confidence: 99%

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

et al. 2021

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A quasi-axisymmetric stellarator, the CFQS, has been designed as a joint project of the National Institute for Fusion Science and Southwest Jiaotong University to prove intrinsic advantages of quasi-axisymmetry. Principal parameters of the CFQS are as follows: the major radius is 1 m, the magnetic field strength is 1 T, the aspect ratio is 4, and the toroidal periodic number is 2. The magnetic field configuration is designed based on that of the CHS-qa. Enhanced confinement properties within the context of neoclassical theory are achieved by its quasi-axisymmetric configuration. In the entire radial range, the magnetic well is retained to keep favourable stability features in the magnetohydrodynamic equilibrium. A magnetic field coil system was designed for the CFQS, which consists of 16 modular coils, 12 toroidal field coils, and 4 poloidal field coils. The supporting structure is designed to withstand strong electromagnetic force under 1 T operation, maintaining enough space for heating and diagnostic systems. The mock-up modular coil with the most complicated shape was constructed by Hefei Keye Electro Physical Equipment Manufacturing Co., Ltd. to check manufacturability and the achieved accuracy. A heat-run test was performed to check the temperature rise of conductors, and the capability of 1 T operation was confirmed. After various tests for the mock-up coil, construction of actual modular coils and the vacuum vessel has begun.

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“…Measurement of energetic ion distribution in the plasma core region is crucial in understanding energetic ion transport and excitation of magnetohydrodynamic instabilities. Under a joint project of the National Institute for Fusion Science and the Southwest Jiaotong University [2], construction of the world's first quasi-axisymmetric stellarator CFQS has begun, based on physics [3][4][5][6][7] and engineering design [8][9][10][11][12][13]. Energetic particle confinement experiments in a quasi-axisymmetric configuration will be possible using beam ions created by a tangential neutral beam injector in CFQS [14].…”

Section: Introductionmentioning

confidence: 99%

Feasibility Study of Deuterium-Deuterium Fusion Profile Diagnostics Using Fusion Born 3 MeV Proton for CFQS

Ogawa

Isobe

Seki

et al. 2022

Plasma and Fusion Research

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A feasibility study for measuring a deuterium-deuterium (D-D) fusion reaction radial profile by promptly lost D-D fusion born 3 MeV protons, whose energy Larmor radius is the same as the minor radius of CFQS, was performed. The Lorentz orbit code was utilized to estimate the predicted signals of collimated proton detectors using the D-D fusion radial profile calculated by the analytical Fokker-Planck code for steady-state plasma FIT3D-DD code. The inversion of the D-D fusion profile using the estimated signals was performed using a linear matrix solution library. The coarse agreement between input and inverted profiles shows the possibility of D-D fusion profile diagnostics by a 3 MeV proton in CFQS.

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The three-dimensional equilibrium with magnetic islands and MHD instabilities in the CFQS quasi-axisymmetric stellarator

Cited by 13 publications

References 28 publications

Simulations of energetic particle driven instabilities in CFQS

Simulations of energetic particle driven instabilities in CFQS

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

Feasibility Study of Deuterium-Deuterium Fusion Profile Diagnostics Using Fusion Born 3 MeV Proton for CFQS

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