Development of a Robust Quasi-Poloidal Compact Stellarator

Strickler, D. J.; Hirshman, S. P.; Spong, D. A.; Cole, M. J.; Lyon, J. F.; Nelson, B. E.; Williamson, D.; Ware, A. S.

doi:10.13182/fst04-a421

Cited by 35 publications

(38 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It was shown there that three mono-energetic viscosity coefficients M * (parallel viscosity against flows), N * (driving force for bootstrap currents), and L * (radial difauthor's e-mail: nishimura.shin@lhd.nifs.ac.jp fusion) are required to describe the full neoclassical characteristics of general non-symmetric toroidal configurations. Since existing numerical methods such as variational and Monte Carlo methods for the drift kinetic equation described in the 3-D phase space (poloidal angle θ, toroidal angle ζ, pitch angle ξ) could be applicable [8], the new theory was applied to various types of advanced helical/stellarator configurations [9,10]. However, this step of the development of the moment approach was still in the "basic frame work."…”

Section: Inroductionmentioning

confidence: 99%

“…However, this step of the development of the moment approach was still in the "basic frame work." Although there were many alternative methods for obtaining L * in the collisionless limit (aforementioned ripple diffusions), the other viscosity coefficients could be obtained only by the Drift Kinetic Equation Solver (DKES) code [8][9][10][11]. Similar to the MHD equilibrium code, the neoclassical theory should also be a practically usable tool.…”

Section: Inroductionmentioning

confidence: 99%

“…Similar to the MHD equilibrium code, the neoclassical theory should also be a practically usable tool. Faster and easier estimation methods for the neoclassical quantities are desirable in integrated simulation systems using iterative calculations of the equilibrium and transport [12], configuration optimizations [9], and experimental studies investigating dependences on configurations. Since the viscosities (or resulting neoclassical transport coefficients) are direct consequences of guiding center drift motions, evaluating them is important in understanding the characteristics of the designed magnetic configurations [9,10,13,14].…”

Section: Inroductionmentioning

confidence: 99%

See 2 more Smart Citations

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Nishimura

Mikkelsen

Spong

et al. 2008

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

Previously reported benchmarking examples of the analytical formulae of neoclassical viscosities were presented implicitly assuming applications in a future integrated simulation system of the Large Helical Device (LHD). Therefore, the assumed toroidal period numbers were mainly N = 10. However, in this type of calculation, an implicit (or sometimes explicit) assumption of ι/N 1 is sometimes included. This assumption is included not only in simplified bounce-averaged drift kinetic equations for ripple diffusions, but also in the equation before the averaging for non-bounce-averaged effects determining neoclassical parallel viscosity and banana-plateau diffusions. For clarifying the applicability of the analytical methods for configurations with extremely low toroidal period numbers (required for low aspect ratios), we show recent benchmarking examples in the National Compact Stellarator Experiment (NCSX) with N = 3 and the Quasi-Poloidal Stellarator (QPS) with N = 2.

show abstract

Section: Inroductionmentioning

confidence: 99%

Section: Inroductionmentioning

confidence: 99%

Section: Inroductionmentioning

confidence: 99%

See 1 more Smart Citation

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Nishimura

Mikkelsen

Spong

et al. 2008

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, RFP plasmas in the axisymmetric Reversed Field eXperiment (RFX) [6] are observed [7], [8] to self-organize into a long-lived helical state with greatly improved transport coefficients. The ability to design helically-shaped plasmas to achieve given physics goals has greatly improved over the last quarter century [9], [10], [11]. The improved theoretical tools, and the experiments on MST and RFX imply that another study is timely.…”

Section: Introductionmentioning

confidence: 99%

Use of Helical Fields to Allow a Long Pulse Reversed Field Pinch

Boozer¹,

Pomphrey²

2008

View full text Add to dashboard Cite

The maintenance of the magnetic configuration of a Reversed Field Pinch (RFP) is an unsolved problem. Even a toroidal loop voltage does not suffice to maintain the magnetic configuration in axisymmetry but could if the plasma had helical shaping. The theoretical tools for plasma optimization using helical shaping have advanced, so an RFP could be relatively easily designed for optimal performance with a spatially constant toroidal loop voltage. A demonstration that interesting solutions exist is given.

show abstract

“…In particular, this approach was used in the development of the device Wendelstein 7-X [7] (W7-X) and several conceptual projects of Helias reactors [8], which were designed as W7-X improved and scaled to the reactor size. The so-called "quasi-poloidal" devices [9] exaggerate one of the features of the Wendelstein-type configurations -a large mirror harmonic of the magnetic field (i.e., the harmonic ∝ exp(iN ϕ), where ϕ is the toroidal angle and N is the number of the field periods). Finally, it was found recently that the inward shift of the magnetic axis in the heliotron LHD (Large Helical Device [10]) results in a significant improvement of the particle confinement [11].…”

Section: Introductionmentioning

confidence: 99%

Mitigation of stochastic diffusion losses in optimized stellarators

Tykhyy

Kolesnichenko

Yakovenko

et al. 2007

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Abstract. The stochastic diffusion (SD) resulting from collisionless transformations between locally trapped and locally passing orbits may lead to a significant loss of energetic particles from stellarator plasmas (Beidler C D et al 2001 Phys. Plasmas 8 2731. In this work, a method to mitigate the consequences of SD is suggested. The method consists in changing the shapes of the separatrices between the locally trapped and locally passing states so that most separatrices do not cross the plasma boundary, which is achieved with a suitable modification of the magnetic configuration. It is demonstrated analytically that in this way the particle loss because of the SD may be reduced significantly, even though the SD still occurs. In particular, it is possible to protect fast particles inside a certain radius from SD loss. It is shown that a variation of the electric field can also affect the SD loss. The modifications of the magnetic configuration and the electric field required for the mitigation are quantified for a configuration of the stellarator Wendelstein 7-X.

show abstract

Development of a Robust Quasi-Poloidal Compact Stellarator

Cited by 35 publications

References 17 publications

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Use of Helical Fields to Allow a Long Pulse Reversed Field Pinch

Mitigation of stochastic diffusion losses in optimized stellarators

Contact Info

Product

Resources

About