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Title: Recent advances in stellarator optimization

Abstract

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. Here, we 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 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 bemore » 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. Thus, 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.« less

Authors:
ORCiD logo [1];  [2];  [1];  [1];  [3]; ORCiD logo [4]; ORCiD logo [1];  [5];  [1];  [1];  [1];  [6];  [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Columbia Univ., New York, NY (United States)
  3. Univ. of Illinois, Urbana-Champaign, IL (United States)
  4. Univ. of Maryland, College Park, MD (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. Max Planck Inst. for Plasma Physics, Greifswald (Germany)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1414907
Grant/Contract Number:  
AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; stellarator; optimization; design

Citation Formats

Gates, D. A., Boozer, A. H., Brown, T., Breslau, J., Curreli, D., Landreman, M., Lazerson, S. A., Lore, J., Mynick, H., Neilson, G. H., Pomphrey, N., Xanthopoulos, P., and Zolfaghari, A. Recent advances in stellarator optimization. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa8ba0.
Gates, D. A., Boozer, A. H., Brown, T., Breslau, J., Curreli, D., Landreman, M., Lazerson, S. A., Lore, J., Mynick, H., Neilson, G. H., Pomphrey, N., Xanthopoulos, P., & Zolfaghari, A. Recent advances in stellarator optimization. United States. doi:https://doi.org/10.1088/1741-4326/aa8ba0
Gates, D. A., Boozer, A. H., Brown, T., Breslau, J., Curreli, D., Landreman, M., Lazerson, S. A., Lore, J., Mynick, H., Neilson, G. H., Pomphrey, N., Xanthopoulos, P., and Zolfaghari, A. Fri . "Recent advances in stellarator optimization". United States. doi:https://doi.org/10.1088/1741-4326/aa8ba0. https://www.osti.gov/servlets/purl/1414907.
@article{osti_1414907,
title = {Recent advances in stellarator optimization},
author = {Gates, D. A. and Boozer, A. H. and Brown, T. and Breslau, J. and Curreli, D. and Landreman, M. and Lazerson, S. A. and Lore, J. and Mynick, H. and Neilson, G. H. and Pomphrey, N. and Xanthopoulos, P. and Zolfaghari, A.},
abstractNote = {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. Here, we 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 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. Thus, 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.},
doi = {10.1088/1741-4326/aa8ba0},
journal = {Nuclear Fusion},
number = 12,
volume = 57,
place = {United States},
year = {2017},
month = {10}
}

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