Physics optimization of stellarators

Grieger, G.; Lotz, W.; Merkel, P.; Nührenberg, J.; Sapper, J.; Strumberger, E.; Wobig, H.; Burhenn, R.; Erckmann, V.; Gasparino, U.; Giannone, L.; Hartfuß, H. J.; Jaenicke, R.; Kühner, G.; Ringler, H.; Weller, A.; Wagner, F.

doi:10.1063/1.860481

Cited by 284 publications

(279 citation statements)

References 15 publications

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“…Wendelstein 7-X (W7-X) [1,2,3] is a stellarator [4]; a plasma fusion experiment to exploit the potential of controlled nuclear fusion [5] for the production of energy. The plasma is confined by a strong magnetic field inside the plasma vessel which is nested within a toroidal arrangement of magnetic coils.…”

Section: Introductionmentioning

confidence: 99%

Vacuum leak search on the Wendelstein 7-X cryostat vessel

Baldzuhn

Reimer

Biedermann

et al. 2015

Vacuum

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A new plasma fusion experiment, the Wendelstein 7-X (W7-X) has been built in the Max-Planck Institute for Plasma Physics in Greifswald, Germany. A cryostat vacuum tank, shaped like a torus, hosts 70 superconducting magnetic coils to produce a toroidal magnetic field that will confine a fusion relevant plasma. The cryostat tank has a volume of about 420 m 3 and is equipped with several hundreds of vacuum ports, feedthroughs and service openings. Nested inside the cryostat is the plasma vessel with a volume of about 80 m 3 , also shaped like a torus. This plasma vessel is connected to the outside by 254 ports that traverse the cryostat. These ports are needed as access for plasma diagnostics, plasma heating and the supply of cooling media. We report in this paper on the vacuum leak search on the W7-X cryostat, both for the internal piping as well as the integral leak search of the entire vessel against air. This is the initial leak search prior to the first cool-down of W7-X. Emphasis is put on the description of the methods, rather than on the results. The technical commissioning of the cryostat vacuum system within a limited time was the primary task; the emphasis was therefore much more on achieving practical results (the leak-tightness) rather than answering fundamental questions.

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Section: Introductionmentioning

confidence: 99%

Vacuum leak search on the Wendelstein 7-X cryostat vessel

Baldzuhn

Reimer

Biedermann

et al. 2015

Vacuum

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“…The scale of the fast-particle confinement problem is clearly shown in [29], which found all trapped alpha particles to be lost in ∼ 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 reactor parameters can be estimated as ≥ 0.1s. Fast particle confinement in modern optimized designs such as W7-X and NCSX is much improved compared to conventional stellarators [30], but remains one of the main challenges for the concept. For instance, alpha confinement remained one of the most serious concerns expressed in the ARIES-CS reactor study [31], even though the ARIES design was able to reduce alpha losses to 5% over a slowing-down time.…”

Section: Energetic Ion Confinementmentioning

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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“…Relevant instabilities which remain are resistive interchange and ballooning modes (ideal and resistive) [5]. Since in the W7-X configuration the magnetic shear is small, the stability of such modes relies in particular on a sufficiently strong magnetic well.…”

Section: Good Magneto-hydro-dynamic (Mhd) Stabilitymentioning

confidence: 99%

“…Within the family of optimized stellarators the quasi-isodynamic Wendelstein 7-X (W7-X) design is based on the minimization of all internal plasma currents (except the diamagnetic current) [5], while the quasi-toroidal National Compact Stellarator Experiment (NCSX) relies on a large bootstrap current to generate the desired rotational transform [6]. Table 1 1).…”

Section: Introductionmentioning

confidence: 99%

A stellarator reactor based on the optimization criteria of Wendelstein 7-X

Wolf

Team

2008

Fusion Engineering and Design

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Wendelstein 7-X is an optimized stellarator including a divertor concept for energy and particle exhaust. The main properties of Wendelstein 7-X are discussed in the context of the application to a stellarator fusion reactor -the Helical Advanced Stellarator concept which is based on the same optimization criteria as Wendelstein 7-X. Experience gained from the design, construction of components and the starting assembly of Wendelstein 7-X is presented.

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Physics optimization of stellarators

Cited by 284 publications

References 15 publications

Vacuum leak search on the Wendelstein 7-X cryostat vessel

Vacuum leak search on the Wendelstein 7-X cryostat vessel

Recent advances in stellarator optimization

A stellarator reactor based on the optimization criteria of Wendelstein 7-X

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