Free-boundary ideal MHD stability of W7-X divertor equilibria

Nührenberg, C.

doi:10.1088/0029-5515/56/7/076010

Cited by 19 publications

(18 citation statements)

References 29 publications

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“…W7-X was optimized in such away that most magnetic configurations have a high threshold for ideal-MHD instability (Nührenberg 2016). It is, therefore, important to establish whether kinetic effects can destabilize ballooning modes for s lower than the ideal ones.…”

Section: Numerical Results For W7-xmentioning

confidence: 99%

“…behaviour of KBM in the stellarator might be far from general, since we cannot claim that we have investigated all possible configurations and parameters. W7-X was optimized in such away that most magnetic configurations have a high threshold for ideal-MHD instability (Nührenberg 2016). It is, therefore, important to establish whether kinetic effects can destabilize ballooning modes for βs lower than the ideal ones.…”

Section: Scan In Radial Wavenumbermentioning

confidence: 99%

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Kinetic ballooning modes in tokamaks and stellarators

et al. 2018

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Kinetic ballooning modes (KBMs) are investigated by means of linear electromagnetic gyrokinetic (GK) simulations in the stellarator Wendelstein 7-X (W7-X), for high-$\unicode[STIX]{x1D6FD}$ plasmas, where $\unicode[STIX]{x1D6FD}$ is the ratio of thermal to magnetic plasma pressure. The analysis shows suppression of ion-temperature-gradient (ITG) and trapped particle modes (TEM) by finite-$\unicode[STIX]{x1D6FD}$ effects and destabilization of KBMs at high $\unicode[STIX]{x1D6FD}$. The results are compared with a generic tokamak case. We show that, for large pressure gradients, the frequency of KBMs evaluated by the GENE code is in agreement with the analytical prediction of the diamagnetic modification of the ideal magnetohydrodynamic limit in W7-X general geometry. Thresholds for destabilization of the KBM are predicted for different W7-X equilibrium configurations. We discuss the relation of these thresholds to the ideal magnetohydrodynamic (MHD) stability properties of the corresponding equilibria.

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Section: Numerical Results For W7-xmentioning

confidence: 99%

Section: Scan In Radial Wavenumbermentioning

confidence: 99%

Kinetic ballooning modes in tokamaks and stellarators

et al. 2018

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“…A simulation for such a 20 MW heating scenario is shown in Figure 8. The prediction is likely not directly relevant for operation, since its predicted

⟨ β ⟩

of 6.4% presumably is not MHD stable, 43 but if the anomalous transport assumptions are not too optimistic, then this shows that W7-X will be able to test its β limits, expected at

⟨ β ⟩ = 5 %

for optimized conditions, with the planned power upgrades to the device. As a side note, this scenario has a predicted triple product of

3.0 \times 10^{20}

m –3 keV s, smaller than the just discussed 10 MW discharge scenario.…”

Section: Expected Triple Products Ion Temperatures and Pulse Lengthsmentioning

confidence: 99%

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

et al. 2017

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The first physics operation phase on the stellarator experiment Wendelstein 7-X was successfully completed in March 2016 after about 10 weeks of operation. Experiments in this phase were conducted with five graphite limiters as the primary plasma-facing components. Overall, the results were beyond the expectations published shortly before the start of operation [Sunn Pedersen et al., Nucl. Fusion 55, 126001 (2015)] both with respect to parameters reached and with respect to physics themes addressed. We report here on some of the most important plasma experiments that were conducted. The importance of electric fields on global confinement will be discussed, and the obtained results will be compared and contrasted with results from other devices, quantified in terms of the fusion triple product. Expected values for the triple product in future operation phases will also be described and put into a broader fusion perspective.

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“…In addition, studying the physics of the electron-cyclotron heating at third harmonics is of interest. The magnetohydrodynamic (MHD) stability studies (Nührenberg 2016) and high-beta equilibrium investigations (Geiger et al. 2015) need more magnetic configuration space of W7-X than is available at 2.5 T.…”

Section: Introductionmentioning

confidence: 99%

First experiments on ICRF discharge generation by a W7-X-like antenna in the Uragan-2M stellarator

Moiseenko

Kovtun

Wauters³

et al. 2020

J. Plasma Phys.

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In support of the ICRF experiments planned on the Wendelstein 7-X (W7-X) stellarator, i.e. fast ion generation, wall conditioning, target plasma production and heating, a first experimental study on plasma production has been made in the Uragan-2M (U-2M) stellarator using W7-X-like two-strap antenna. In all the experiments, antenna monopole phasing was used. The W7-X-like antenna operation with launched radiofrequency power of ~100 kW have been performed in helium (p = (4–14) × 10−2 Pa) with the vacuum vessel walls pre-loaded with hydrogen. Production of plasma with a density higher than 1012 cm−3 was observed near the first harmonic of the hydrogen cyclotron frequency. Operation at first hydrogen harmonic is feasible in W7-X future ICRF experiments.

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Free-boundary ideal MHD stability of W7-X divertor equilibria

Cited by 19 publications

References 29 publications

Kinetic ballooning modes in tokamaks and stellarators

Kinetic ballooning modes in tokamaks and stellarators

Key results from the first plasma operation phase and outlook for future performance in Wendelstein 7-X

First experiments on ICRF discharge generation by a W7-X-like antenna in the Uragan-2M stellarator

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