Spectral Asymmetry Due to Magnetic Coordinates

Park, Jong‐Kyu; Boozer, Allen H.; Ménard, J.

doi:10.2172/959387

Cited by 3 publications

(3 citation statements)

References 15 publications

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“…A typical numerical modelling scenario involves the study of plasma dynamics between two flux-surfaces ψ 0 and ψ 1 . Structured and unstructured numerical grids have been proposed for the numerical discretization of this region [9,10,11,12,13,14,15,16]. Let us emphasize, however, that the algorithms developed are in no way restricted to magnetic fusion applications.…”

Section: Introductionmentioning

confidence: 99%

Streamline integration as a method for two-dimensional elliptic grid generation

Wiesenberger

Held

Einkemmer

2017

Journal of Computational Physics

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We propose a new numerical algorithm to construct a structured numerical elliptic grid of a doubly connected domain. Our method is applicable to domains with boundaries defined by two contour lines of a two-dimensional function. The resulting grids are orthogonal to the boundary. Grid points as well as the elements of the Jacobian matrix can be computed efficiently and up to machine precision. In the simplest case we construct conformal grids, yet with the help of weight functions and monitor metrics we can control the distribution of cells across the domain. Our algorithm is parallelizable and easy to implement with elementary numerical methods. We assess the quality of grids by considering both the distribution of cell sizes and the accuracy of the solution to elliptic problems. Among the tested grids these key properties are best fulfilled by the grid constructed with the monitor metric approach.

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Section: Introductionmentioning

confidence: 99%

Streamline integration as a method for two-dimensional elliptic grid generation

Wiesenberger

Held

Einkemmer

2017

Journal of Computational Physics

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“…However, the resonant components of the field, which correspond directly to the width of the magnetic islands on the mode-rational surfaces [21], are not coordinate dependent. This has been shown to be true when considering different magnetic coordinate systems [22], and it is also true for arbitrary rigid displacements of a magnetic coordinate system (or equivalently, a rigid displacement of the plasma and magnets). This is discussed in more detail in section 3.3.…”

Section: Error Field Spectrummentioning

confidence: 83%

Error field impact on mode locking and divertor heat flux in NSTX-U

et al. 2019

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During the 2016 NSTX-U experimental campaign, locked modes in the plasma edge presented clear evidence of the presence of error fields. Extensive metrology and plasma response modeling with IPEC and M3D-C1 have been conducted to understand the various sources of error fields in NSTX-U as built in 2016, and to determine which of these sources have the greatest effect on the plasma. In particular, modeling finds that the error field from misalignment of the toroidal field (TF) coils may have a significant effect on the plasma. The response to the TF error field is shown to depend on the presence of a q = 1 surface, in qualitative agreement with experimental observations. It is found that certain characteristics of the TF error field present new challenges for error field correction. Specifically, the error field spectrum differs significantly from that of coils on the low-field side (such as the NSTX-U error field correction coils), and does not resonate strongly with the dominant kink mode, thus potentially requiring a multi-mode correction. Furthermore, to mitigate heat fluxes using poloidal flux expansion, the pitch angle at the divertor plates must be small (∼1 • ). It is shown that uncorrected error fields may result in potentially significant local perturbation to the pitch angle. Estimates for coil alignment tolerances in NSTX-U are derived based on consideration of both heat flux and core resonant fields independently.

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“…where 𝐵 𝑡𝑜𝑟 is the unperturbed toroidal field on the magnetic axis of the device [5][6], while 𝐵 1,1 , 𝐵 1,2 and 𝐵 1,3 are the spectral components of 3D complex Fourier space [7] defined as:…”

Section: Efs Quantitative Descriptionmentioning

confidence: 99%