Resistive MHD modelling of the quasi-single helicity state in the KTX regimes

Luo, Bing; Zhu, Ping; Li, Hong; Liu, Wandong; Team, Ktx

doi:10.1088/1741-4326/aa9291

Cited by 5 publications

(5 citation statements)

References 39 publications

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“…It is significant to observe that near the helical axis, especially for the QSH in RFP, the plasma confinement is superior [3], implying the existence of good flux surfaces in this region. This is also confirmed by time dependent simulations using realistic plasma parameters [4,5]. At the present time, the good confinement region in the QSH state covers only a limited portion of the plasma.…”

Section: Introductionsupporting

confidence: 82%

“…As explained in the previous section, for a system with κ a = κa , the metric for the line element is given by equation (5). When ρ τa is small, the remarkable feature of the lowest order approximation to the metric, equation (7), is that all the metric tensor elements are independent of s. Therefore, we may seek a solution to the equilibrium equation that is independent of s. In this system, flux surfaces are guaranteed to exist.…”

Section: Lowest Order Equilibrium With the Approximate Metric-the Gen...mentioning

confidence: 99%

“…It is expected that this scheme could become complicated quite quickly. An alternative strategy is to use the lowest and/ or the first order solutions as a guide and starting point for the 3D numerical solution [17,18] to the equilibrium problem with the full metric equation (5). In this way, we use the metric with the known possibility of good asymptotic flux surfaces when the axis curve has a constant curvature.…”

Section: An Alternative Strategymentioning

confidence: 99%

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A three-dimensional magnetohydrodynamic equilibrium in an axial coordinate with a constant curvature

et al. 2019

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Motivated by the superior confinement observed in the relaxed three dimensional (3D) states in the reversed field pinch, 3D plasma equilibria in coordinate systems based on space curves with a constant curvature as the axial coordinates are studied by using the method of metric perturbation. Constancy of the curvature allows the development of magnetohydrodynamic equilibrium with asymptotic good 2D flux surfaces near the coordinate axis. The perturbation parameter is the product of the torsion variation along the coordinate axis and the distance from it. The lowest order equilibrium with good 2D flux surfaces is symmetric with respect to translation along the space curve. It embodies the approximate toroidal-helical symmetry and is determined by a generalized Grad–Shafranov equation which includes information of the constant curvature and the average torsion of the space curve. Based on this fundamental equilibrium, a formal scheme is developed that allows us to find the ideal MHD equilibrium taking into account the full metric variation of the torsion along the spatial axis. In this limit, the flux surfaces are shown to exist for the full plasma. Numerical examples are given for the lowest order equilibria. It is suggested that equilibria based on this type of coordinates can allow easier evaluation of plasma shapes and magnetic boundary conditions that are more compatible with the relaxed central core. This could be the needed requirement for strongly self-organized equilibria with a large good confinement region.

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Section: Introductionsupporting

confidence: 82%

Section: Lowest Order Equilibrium With the Approximate Metric-the Gen...mentioning

confidence: 99%

Section: An Alternative Strategymentioning

confidence: 99%

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A three-dimensional magnetohydrodynamic equilibrium in an axial coordinate with a constant curvature

et al. 2019

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“…The kinetic effects of EP are included in the hybrid kinetic-MHD model by adding the EP pressure tensor P h in the momentum equation, and P h is calculated using δf PIC method. The NIMROD code has been extensively applied to study MHD instabilities and EP instabilities [23][24][25][26][27], the details of the model in NIMROD are described in the next section.…”

Section: Introductionmentioning

confidence: 99%

Investigation of ion fishbone stability on HL-2A using NIMROD

Yang

Hou

Chen

2019

Plasma Sci. Technol.

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Numerical calculations of resistive internal kink mode with effects of energetic particles (EPs) on HL-2A have been performed using the hybrid kinetic-MHD model inplemented in the NIMROD code. The m/n=1/1 resistive internal kink mode is unstable in MHD limit. However, with kinetic effects of energetic ions, a fishbone mode is excited with mode frequency around 10 kHz. We calculate the impact of resistivity on the growth rate and frequency of ion fishbone mode, and the results are in good agreement with the analytic solutions, which are obtained by solving the fishbone dispertion relation including resistivity effect. The effects of β frac and cut off velocity of EP on fishbone mode are calculated in detail, where β frac is the ratio of EP pressure to background plasma pressure. This work presents a clear explanation of the stabilizing effect of ECRH on ion fishbone, which is first observed on HL-2A.

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“…The KTX is a new RFP device with a major radius of R = 1.4 m and a minor radius of a = 0.4 m. [9,[11][12][13] The materials of the first wall and limiter are stainless steel and molybdenum, respectively. The height of the poloidal and toroidal molybdenum limiters is 2 cm.…”

Section: Experimental Setup and Laboratory Testsmentioning

confidence: 99%

Construction of an H α diagnostic system and its application to determine neutral hydrogen densities on the Keda Torus eXperiment*

Zhu¹,

Lan²,

Zhuang³

et al. 2019

Chinese Phys. B

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A 10-channel H α diagnostic system has been designed with the rapid response rate of 300 kHz, spatial resolution of about 40 mm, and overlap between adjacent channels of about 3%, and it has been implemented successfully on Keda Torus eXperiment (KTX), a newly constructed, reversed field pinch (RFP) experimental device at the University of Science and Technology of China (USTC). This diagnostic system is a very important tool for the initial KTX operations. It is compact, with an aperture slit replacing the traditional optical lens system. A flexural interference filter is designed to prevent the center wavelength from shifting too much as the increase of angle from vertical incidence. To eliminate the stray light, the interior of the system is covered with the black aluminum foil having a very high absorptivity. Using the H α emission data, together with the profiles of electron temperature and density obtained from the Langmuir probe, the neutral density profiles have been calculated for KTX plasmas. The rapid response rate and good spatial resolution of this H α diagnostic system will be beneficial for many studies in RFP plasma physics.

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Resistive MHD modelling of the quasi-single helicity state in the KTX regimes

Cited by 5 publications

References 39 publications

A three-dimensional magnetohydrodynamic equilibrium in an axial coordinate with a constant curvature

A three-dimensional magnetohydrodynamic equilibrium in an axial coordinate with a constant curvature

Investigation of ion fishbone stability on HL-2A using NIMROD

Construction of an H α diagnostic system and its application to determine neutral hydrogen densities on the Keda Torus eXperiment*

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