Magnetic Fields with Precise Quasisymmetry for Plasma Confinement

Landreman, Matt; Paul, Elizabeth

doi:10.1103/physrevlett.128.035001

Cited by 81 publications

(210 citation statements)

References 36 publications

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“…One single-stage optimization approach was demonstrated in Giuliani et al (2020), based on the near-axis expansion for quasi-symmetry in Garren & Boozer (1991); Landreman & Sengupta (2018); Landreman et al (2019); Landreman & Sengupta (2019). This approach was motivated by the fact that quasi-symmetric magnetic fields are known to have good confinement properties (Helander 2014;Landreman & Paul 2022). We demonstrated that this single-stage method effectively produced vacuum quasisymmetric magnetic fields in the vicinity of the magnetic axis.…”

Section: Introductionmentioning

confidence: 88%

Direct computation of magnetic surfaces in Boozer coordinates and coil optimization for quasi-symmetry

Giuliani,

Wechsung,

Landreman

et al. 2022

Preprint

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We propose a new method to compute magnetic surfaces that are parametrized in Boozer coordinates for vacuum magnetic fields. We also propose a measure for quasisymmetry on the computed surfaces and use it to design coils that generate a magnetic field that is quasi-symmetric on those surfaces. The rotational transform of the field and complexity measures for the coils are also controlled in the design problem. Using an adjoint approach, we are able to obtain analytic derivatives for this optimization problem, yielding an efficient gradient-based algorithm. Starting from an initial coil set that presents nested magnetic surfaces for a large fraction of the volume, our method converges rapidly to coil systems generating fields with excellent quasi-symmetry and low particle losses. In particular for low complexity coils, we are able to significantly improve the performance compared to coils obtained from the standard two-stage approach, e.g. reduce losses of fusion-produced alpha particles born at half-radius from 17.7% to 6.6%. We also demonstrate 16-coil configurations with alpha loss < 1% and neoclassical transport magnitude 3/2 eff less than approximately 5 × 10 −9 .

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Section: Introductionmentioning

confidence: 88%

Direct computation of magnetic surfaces in Boozer coordinates and coil optimization for quasi-symmetry

Giuliani,

Wechsung,

Landreman

et al. 2022

Preprint

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“…We can test this criterion through a practical example. Take the magnetic axis from the QA design in [39] (the so-called precise QA) obtained directly from the VMEC files, and write the leading three harmonics: R {2,4,6} = {0.184, 0.0217, 0.00260} and Z {2,4,6} = {0.158, 0.0206, 0.00256}. First, we note that, as we hypothesized, R n ∼ Z n .…”

Section: Practical Application and Qualitative Assessmentmentioning

confidence: 92%

“…Generally, we shall not need to deal with all the complex, intermediate phases, as strong shaping tends to make them impractical. Using the precise QH in [39] as a testbed, R {4,8,12,16} = {0.200, 0.0314, 0.00467, 0.000559} and Z {4,8,12,16} = {0.179, 0.0286, 0.00431, 0.000528}. The measure s is {3.4, 2.0, 0.7, 0.1}.…”

Section: Practical Application and Qualitative Assessmentmentioning

confidence: 99%

Phases and phase-transitions in quasisymmetric configuration space

Rodriguez¹,

Sengupta²,

Bhattacharjee³

2022

Preprint

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“…Now, Matt Landreman at the University of Maryland, College Park, and Elizabeth Paul at Princeton University have given a boost to an alternative kind of fusion reactor called a stellarator. Using a numerical model, the researchers show that a particular magnetic-field arrangement, referred to as quasisymmetry, which allows long-term plasma confinement, can be achieved in a stellarator much more precisely than previously thought [2].…”

mentioning

confidence: 99%

“…Previous numerical attempts to achieve quasisymmetry have mainly been based on minimizing the symmetry-breaking Fourier components of the scalar amplitude of the magnetic field in Boozer coordinates at each iteration. Landreman and Paul approach the problem by numerically minimizing an objective function that includes the toroidal and poloidal currents inside a magnetic surface [2]. Their result is a breakthrough because they find certain parameter combinations that achieve quasisymmetry more precisely than any previous efforts.…”

mentioning

confidence: 99%