Web Services for 3D MHD Equilibrium Data at Wendelstein 7-X

Grahl, M.; Svensson, J.; Werner, A.; Andreeva, T.; Bozhenkov, S.; Drevlak, M.; Geiger, J.; Krychowiak, M.; Turkin, Y.

doi:10.1109/tps.2017.2784903

Cited by 14 publications

(15 citation statements)

References 18 publications

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“…To map data of the profile diagnostics to flux surfaces, coordinate transformations based on results of the equilibrium code VMEC [63] are applied in this work. At W7-X, VMEC is available as a web-service [64], together with a wide data base of precomputed equilibria. In particular, the VMEC data base includes equilibria for reference magnetic configurations with a vanishing plasma pressure, referred to as vacuum equilibria, which provide an adequate accuracy for plasmas at low parameters.…”

Section: Description Of the Experimental Conditionsmentioning

confidence: 99%

High-performance plasmas after pellet injections in Wendelstein 7-X

Bozhenkov¹,

Kazakov²,

Ford³

et al. 2020

Nucl. Fusion

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102

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A significant improvement of plasma parameters in the optimized stellarator W7-X is found after injections of frozen hydrogen pellets. The ion temperature in the post-pellet phase exceeds 3 keV with 5 MW of electron heating and the global energy confinement time surpasses the empirical ISS04-scaling. The plasma parameters realized in such experiments are significantly above those in comparable gas-fuelled discharges. In this paper, we present details of these pellet experiments and discuss the main plasma properties during the enhanced confinement phases. Local power balance is applied to show that the heat transport in post-pellet phases is close to the neoclassical level for the ion channel and is about a factor of two above that level for the combined losses. In comparable gas-fuelled discharges, the heat transport is by about ten times larger than the neoclassical level, and thus is largely anomalous. It is further observed that the improvement in the transport is related to the peaked density profiles that lead to a stabilization of the ion-scale turbulence.

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Section: Description Of the Experimental Conditionsmentioning

confidence: 99%

High-performance plasmas after pellet injections in Wendelstein 7-X

Bozhenkov¹,

Kazakov²,

Ford³

et al. 2020

Nucl. Fusion

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102

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“…The first preparative step for the equilibrium modelling w a s a m a p p i n g o f t h e e x p e r i m e n t a l d e n s i t y a n d temperature profiles in order to obtain the pressure profiles necessary for the VMEC [8] runs. The standard quick procedure to map diagnostic data is to use the precalculated equilibria available via W7-X web services [9]. In the web services data collection, the pre-calculated equilibria can be found for all W7-X main reference configurations for different theoretical pressure profiles and different beta values.…”

Section: Mapping Of the Diagnostic Data And Equilibrium Evaluationmentioning

confidence: 99%

Equilibrium evaluation for Wendelstein 7-X experiment programs in the first divertor phase

Andreeva

Alonso

Bozhenkov

et al. 2019

Fusion Engineering and Design

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Wendelstein 7-X (W7-X) is a modular advanced stellarator, which successfully went into operation in December 2015 at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany, and continued to thrive at the experimental campaign with the first divertor phase in August-December 2017. The nested magnetic surfaces in W7-X are created by a system of 3-D toroidally discrete coils, providing both toroidal and poloidal field components, and designed with the aim to create optimum equilibrium properties. The optimization criteria included the high quality of vacuum magnetic surfaces, good finite beta equilibrium and MHD-stability properties as well as a substantial reduction of the neoclassical transport and bootstrap current in comparison to classical stellarators.Equilibrium calculations, devoted to the analysis of the experiment programs dedicated to measure the bootstrap current, were performed with help of the Variational Moments Equilibrium Code, available as Wendelstein 7-X web service. Pressure profiles based on experimental data served as an input for calculations. The mapping of measurements using precalculated equilibria for different beta values has been analyzed. A comparison with reconstruction results obtained by means of the Minerva Framework, considering only experimental data of magnetics measurements, and the V3FIT code is presented.

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“…Magnetic field equilibrium and plasma profiles. The needed 3D-MHD equilibria were computed with VMEC (Variational Moments Equilibrium Code) [29] and interfaced to the calculation via the W7-X VMEC webservice [33]. The used density and temperature profiles of electrons and ions are shown in figure 3.…”

Section: Atomic Collisionsmentioning

confidence: 99%

“…The vessel geometry and wall intersection checks are provided by the W7-X webservices ComponentsDB and MeshSrv [33,34].…”

Section: Atomic Collisionsmentioning

confidence: 99%

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

Bannmann¹,

Bozhenkov²,

Äkäslompolo³

et al. 2022

J. Inst.

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A preliminary study investigating capabilities of a planned but not yet installed neutral particle analyzer (NPA) [1,2] system combined with a diagnostic neutral beam at Wendelstein 7-X (W7-X) [3] is presented. Additionally two NPAs viewing the neutral beam injection (NBI) [4] source 8 beam and using it as neutral source are studied. The main focus is laid on what information about NBI fast-ion slowing down distributions can be inferred from active NPA measurements when altering the magnetic configuration, plasma β, density, electron temperature or radial electric field. For an order of magnitude estimation of the passive signal a model for penetration of neutral hydrogen recycling from the first wall is implemented. For the active signal a diagnostic neutral beam injector was simulated using FIDASIM [5]. The fast-ion slowing down distributions were calculated with ASCOT [6]. The synthetic NPA signal is found in general to be sensitive to changes in the fast-ion distribution function. Distinct features can be seen in the high energy active signal in the high-mirror configuration when changing β, especially, when looking at deeply trapped fast particles. However, for the initially planned installation geometry of the NPA diagnostic most fast-ion distributions exhibit only small differences in the magnitude and especially shape. In a high density case in the standard magnetic configuration with a central β of 8%, the fast-ion density in the core region is too low to provide a measurable flux of charge exchanged neutrals. The passive signal from the inner plasma regions is found to be negligible compared to the active signal.

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Web Services for 3D MHD Equilibrium Data at Wendelstein 7-X

Cited by 14 publications

References 18 publications

High-performance plasmas after pellet injections in Wendelstein 7-X

High-performance plasmas after pellet injections in Wendelstein 7-X

Equilibrium evaluation for Wendelstein 7-X experiment programs in the first divertor phase

Feasibility of neutral particle analysis for fast-ion measurements at W7-X

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