Tracking of the magnet system geometry during Wendelstein 7-X construction to achieve the designed magnetic field

Andreeva, T.; Bräuer, T.; Bykov, V.; Egorov, K.; Endler, M.; Fellinger, J.; Kißlinger, J.; Köppen, M.; Schauer, F.

doi:10.1088/0029-5515/55/6/063025

Cited by 27 publications

(32 citation statements)

References 9 publications

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“…The largest coil placement errors were less than 4.4 mm, resulting in an expected largest Fourier coefficient of the magnetic perturbation error of b 11 ≈1.2 × 10 −4 (ref. 26). …”

Section: Resultsmentioning

confidence: 99%

Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

et al. 2016

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Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good confinement is realized, and that the measured deviations are smaller than one part in 100,000. This is a significant step forward in stellarator research, since it shows that the complicated and delicate magnetic topology can be created and verified with the required accuracy.

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“…The largest coil placement errors were less than 4.4 mm, resulting in an expected largest Fourier coefficient of the magnetic perturbation error of b 11 ≈1.2 × 10 −4 (ref. 26). …”

Section: Resultsmentioning

confidence: 99%

Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

et al. 2016

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“…cycles. Present results of error field analysis [8] show that the maximal compensation capacities of the trim coils are not necessary. The probability is very low that error field compensation requires such extreme trim coil energizing that the EM forces generated are mainly in such unfavourable direction as given in table 1.…”

Section: Discussionmentioning

confidence: 75%

“…A typical example for the differences in displacements (up to 3.2 mm) of nonplanar coils located in the middle of the modules (type 1 coils) is shown in figure 4. The impact of this asymmetry on the error field is assessed [8] with the conclusion that the capacity of the trim coils is sufficient to mitigate additional deviations introduced by themselves. Due to CSS deformation under EM forces the dead weight of the MS is shifted from a rather even distribution over the cryo-legs from the half-modules HMx0 to double values on supports attached to the odd-numbered HMx1 (see table 2).…”

Section: Trim Coil Operationsmentioning

confidence: 99%

Sliding weight supports for W7-X magnet system: structural aspects

Bykov¹,

Fellinger²,

Egorov³

et al. 2015

Nucl. Fusion

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The Wendelstein 7-X (W7-X) stellarator is presently under commissioning at the Max-Planck-Institut für Plasmaphysik in Greifswald. The coil system consisting of 70 superconducting coils of seven different types is supported by a massive central support structure (CSS), and thermally protected by the cryostat. The magnet system weight is borne by supports which are bolted to the cold CSS. These ten so-called cryo-legs penetrate through the cryostat wall to the warm machine base. The design of the cryo-legs incorporates glass-reinforced plastic tubes to guarantee relatively small thermal conductivity. In order to ensure free thermal shrinkage of the magnet system and to reduce stresses in the cryo-legs, sliding and rotating bearings are used as interfaces to the machine base. Tie-rods between the machine base and the warm ends of the cryo-legs prevent toroidal rotation of the magnet system, as well as any other horizontal shifts due to asymmetric loads. The assembly of the magnet system introduced some vertical imperfections in the cryo-leg positions causing considerable additional internal stresses which were not considered during the design stage. In addition, originally not planned trim coils induce unsymmetrical cyclic loads. Therefore, the previously used method to analyse one magnet system module with periodical boundary conditions is not applicable. Consequently, a model of the complete magnet system, including all five modules, was created and analysed. Fatigue analyses of the cryo-legs under the new cyclic loads, applied on top of the approximately 100 t static weight, have been performed in order to evaluate the lifetime. The paper presents the progress in structural analyses of the W7-X magnet system under the as-built conditions, loads due to the trim coil operation, and results of the weight support fatigue analysis.

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“…To cover the expected range of possible structural parameter variations of W7-X magnet system, the 72° ANSYS Global Model was used. Taking into account results of all these simulations, the final level of the magnetic field perturbation can be estimated as (1.21 ± 0.34 ± 0.3) •10 -4 [8], which is well below the compensation capacities of the installed trim coils. In addition, the assessment of the magnet system deformation under electromagnetic forces due to the operation of the trim coils was performed.…”

Section: A Tolerances Of the Magnetic Fieldmentioning

confidence: 95%

Engineering Challenges in W7-X: Lessons Learned and Status for the Second Operation Phase

Bosch

Andreeva

Brakel

et al. 2018

IEEE Trans. Plasma Sci.

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In 2015 the optimized stellarator Wendelstein 7-X stellarator (W7-X) started with operation. The main objective of W7-X is the demonstration of the integrated reactor potential of the optimized stellarator line. An important element of this mission is the achievement of high heating-power and high confinement in steady-state operation. The approach to this mission is following three steps. First plasmas were produced in a limiter configuration (OP 1.1), then a test divertor unit is being installed (TDU) for the next campaign, OP 1.2, before the full steady state capability will be achieved implementing active cooling of all in-vessel components and a steady state high heat flux divertor. In December 2015, the first helium plasma was generated using Electron Cyclotron Resonance Heating (ECRH), in February 2016 the working gas was switched to hydrogen. The first operation phase (OP 1.1) was successfully finished in March 2016. At the end of OP 1.1 the discharge duration was close to 6 seconds, the limit for the integrated heating power was increased to 4 MJ and electron temperatures of ~10 keV were achieved. Due to the low densities in the range of 10 19 cm-3 and the pure electron heating by ECRH, the ion temperatures reached only 2 keV. At present, W7-X is undergoing the next completion phase, including the installation of the test divertor unit, the installation of the carbon tiles on the inner plasma vessel wall, an upgrade of existing diagnostics and the installation of new diagnostics. This paper discusses the first operational phase, lessons learned and implemented and the status before the start of the second operational phase (OP 1.2).

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Tracking of the magnet system geometry during Wendelstein 7-X construction to achieve the designed magnetic field

Cited by 27 publications

References 9 publications

Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

Sliding weight supports for W7-X magnet system: structural aspects

Engineering Challenges in W7-X: Lessons Learned and Status for the Second Operation Phase

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