Engineering optimization of stellarator coils lead to improvements in device maintenance

Brown, Thomas G.; Breslau, J.; Gates, D.; Pomphrey, N.; Zolfaghari, A.

doi:10.1109/sofe.2015.7482426

Cited by 26 publications

(29 citation statements)

References 3 publications

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“…The design of acceptable coils is clearly more computationally demanding for stellarators than for the axisymmetric tokamak. Nevertheless, stellarator coils may be more consistent with reactor requirements than tokamak coils, in particular maintenance access to the plasma chamber (Brown et al 2014). One possibility is to produce most of the magnetic field using a helical coil, which follows the helical trough located on the inboard side of optimized stellarators, that has as many vertical legs as the stellarator has periods.…”

Section: Coilsmentioning

confidence: 99%

Stellarator design

Boozer

2015

J. Plasma Phys.

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This paper is dedicated to Vitaly Shafranov, who became increasingly interested in stellarators. Stellarators have a steady-state magnetic configuration, robust positional stability, and consistency with a plasma current below the level at which runaway electrons become a major issue. The development path for stellarators may be faster and cheaper than for tokamaks: stellarators are amenable to computer design validated by moderate scale experiments to circumvent issues that impede fusion development. This is distinct from the empirical explorations required to find an acceptable nonlinear, self-organized state of a tokamak. Fusion plasmas can be designed and controlled in stellarators in ways that are not possible in tokamaks. This paper outlines computational studies that could be carried at low cost during the next few years that would clarify the reactor potential of the stellarator and are needed for rational planning of the fusion program.

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Section: Coilsmentioning

confidence: 99%

Stellarator design

Boozer

2015

J. Plasma Phys.

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“…The COILOPT [12,13] code, developed for the design of the NCSX coil set [14], optimizes coil filaments on a winding surface which is allowed to vary. COILOPT++ [15] improved upon COILOPT, by defining coils using splines, which allows one to straighten modular coils in order to improve access to the plasma. The need for a winding surface was eliminated with the FOCUS [16] code, which represents coils as 3-dimensional space curves.…”

Section: Introductionmentioning

confidence: 99%

An adjoint method for gradient-based optimization of stellarator coil shapes

et al. 2018

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We present a method for stellarator coil design via gradient-based optimization of the coil-winding surface. The REGCOIL (Landreman 2017 Nucl. Fusion 57 046003) approach is used to obtain the coil shapes on the winding surface using a continuous current potential. We apply the adjoint method to calculate derivatives of the objective function, allowing for efficient computation of analytic gradients while eliminating the numerical noise of approximate derivatives. We are able to improve engineering properties of the coils by targeting the root-mean-squared current density in the objective function. We obtain winding surfaces for W7-X and HSX which simultaneously decrease the normal magnetic field on the plasma surface and increase the surface-averaged distance between the coils and the plasma in comparison with the actual winding surfaces. The coils computed on the optimized surfaces feature a smaller toroidal extent and curvature and increased inter-coil spacing. A technique for visualization of the sensitivity of figures of merit to normal surface displacement of the winding surface is presented, with potential applications for understanding engineering tolerances.

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“…Important improvements to the coil design features of the STELLOPT code, embodied in a new code called COILOPT++, have been used to develop coil designs that are compatible with a large sector maintenance scheme [9]. The process involves coupling explicit engineering constraints into the optimization, which was modified to operate with spline representation of the coils instead of Fourier modes.…”

Section: Improved Coil Designmentioning

confidence: 99%

“…The resultant stellarator coil design with a large sector maintenance scheme is shown in Figure 1, which is taken from reference [9]. The coil optimization was sufficiently successful with modular coils only, that it was not necessary to add trim coils, although the COILOPT++ code supports that possibility.…”

Section: Improved Coil Designmentioning

confidence: 99%

Recent advances in stellarator optimization

et al. 2017

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Computational optimization has revolutionized the field of stellarator design. To date, optimizations have focused primarily on optimization of neoclassical confinement and ideal MHD stability, although limited optimization of other parameters has also been performed.The purpose of this paper is to outline a select set of new concepts for stellarator optimization that, when taken as a group, present a significant step forward in the stellarator concept.One of the criticisms that has been leveled at existing methods of design is the complexity of the resultant field coils. Recently, a new coil optimization code -COILOPT++, which uses a spline instead of a Fourier representation of the coils, -was written and included in the STELLOPT suite of codes. The advantage of this method is that it allows the addition of real space constraints on the locations of the coils. The code has been tested by generating coil designs for optimized quasi-axisymmetric stellarator plasma configurations of different aspect ratios. As an initial exercise, a constraint that the windings be vertical 1 was placed on large major radius half of the non-planar coils. Further constraints were also imposed that guaranteed that sector blanket modules could be removed from between the coils, enabling a sector maintenance scheme. Results of this exercise will be presented.New ideas on methods for the optimization of turbulent transport have garnered much attention since these methods have led to design concepts that are calculated to have reduced turbulent heat loss. We have explored possibilities for generating an experimental database to test whether the reduction in transport that is predicted is consistent with experimental observations. To this end, a series of equilibria that can be made in the now latent QUASAR experiment have been identified that will test the predicted transport scalings. Fast particle confinement studies aimed at developing a generalized optimization algorithm are also discussed. A new algorithm developed for the design of the scraper element on W7-X is presented along with ideas for automating the optimization approach.

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Engineering optimization of stellarator coils lead to improvements in device maintenance

Cited by 26 publications

References 3 publications

Stellarator design

Stellarator design

An adjoint method for gradient-based optimization of stellarator coil shapes

Recent advances in stellarator optimization

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