K. Aleynikova
A5003944263- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Geophysics and Gravity Measurements
- Quantum chaos and dynamical systems
- Nuclear Materials and Properties
- Energetic Materials and Combustion
- Electromagnetic Launch and Propulsion Technology
- Cosmology and Gravitation Theories
- Radiation Effects in Electronics
- Radio Astronomy Observations and Technology
- GNSS positioning and interference
- Atomic and Subatomic Physics Research
- Matrix Theory and Algorithms
- Pulsars and Gravitational Waves Research
- Earthquake Detection and Analysis
- Fluid Dynamics and Turbulent Flows
- Dust and Plasma Wave Phenomena
Max Planck Institute for Plasma Physics - Greifswald
2016-2024
Max Planck Institute for Plasma Physics
2015-2024
Princeton Plasma Physics Laboratory
2021-2023
Max Planck Society
2015-2021
Moscow Institute of Physics and Technology
2017-2018
ITER
2014
Japan External Trade Organization
2014
Abstract The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor and plasma volume) restarted operation after the assembly of a graphite heat shield 10 inertially cooled island divertor modules. This paper reports on results from first high-performance operation. Glow discharge conditioning ECRH discharges in helium turned out to be important for density edge radiation control. Plasma densities with central electron temperatures were routinely achieved...
Abstract Research on magnetic confinement of high-temperature plasmas has the ultimate goal harnessing nuclear fusion for production electricity. Although tokamak 1 is leading toroidal magnetic-confinement concept, it not without shortcomings and community therefore also pursued alternative concepts such as stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) field geometry. The availability this additional dimension opens up an extensive configuration...
After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning device, first plasma operation started at end 2015. Integral start-up using electron cyclotron resonance heating (ECRH) an extensive set diagnostics have been completed, allowing initial physics studies during operational campaign. Both in helium hydrogen, breakdown was easily achieved. Gaining experience with vessel conditioning, discharge lengths could be extended gradually. Eventually,...
Abstract Fusion energy research has in the past 40 years focused primarily on tokamak concept, but recent advances plasma theory and computational power have led to renewed interest stellarators. The largest most sophisticated stellarator world, Wendelstein 7-X (W7-X), just started operation, with aim show that earlier weaknesses of this concept been addressed successfully, intrinsic advantages persist, also at parameters approaching those a future fusion plant. Here we first physics...
Abstract We present recent highlights from the most operation phases of Wendelstein 7-X, advanced stellarator in world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens seconds. Pellet fueling allows plasma reduced ion-temperature-gradient turbulence, during such phases, overall is so (energy often 200 ms) that attained density temperature profiles would not possible less optimized devices, since...
Relativistic electron (RE) beams at high current density (low safety factor, qa) yet very low free-electron accessed with D2 secondary injection in the DIII-D and JET tokamak are found to exhibit large-scale MHD instabilities that benignly terminate RE beam. In JET, this technique has enabled termination of MA-level currents without measurable first-wall heating. This scenario thus offers an unexpected alternate pathway achieve mitigation collisional dissipation. Benign is explained by two...
Abstract An important question for the outlook of stellarator reactors is their robustness against pressure driven modes, and underlying mechanism behind experimentally observed soft β limits. Towards building a robust answer to these questions, simulation studies are presented using recently derived reduced nonlinear MHD model. First, initial model implementation extended capture fluid compression by including influence parallel flows. Linear benchmarks (2, 1) tearing mode in W7-AS...
Abstract In the Wendelstein 7-X stellarator (W7-X), two related global low-frequency electromagnetic oscil-
lations are observed on many diagnostic systems (e.g. plasma stored energy, Mirnov coils, Langmuir
probes, etc.). The activity is to presence of magnetic islands at certain radii. However, in
contrast initial analyses in earlier works, mode not localized islands,
but rather an m = 1 type outer-core. We observe a strong cross-correlation...
Abstract After a long device enhancement phase, scientific operation resumed in 2022. The main new components are the water cooling of all plasma facing and water-cooled high heat flux divertor units. Water allowed for first long-pulse campaign. A maximum discharge length 8 min was achieved with total heating energy 1.3 GJ. Safe demonstrated attached detached mode. Stable detachment is readily some magnetic configurations but requires impurity seeding small pitch angle within edge islands....
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 is ratio thermal to magnetic plasma pressure. The analysis shows suppression ion-temperature-gradient (ITG) and trapped particle (TEM) finite- effects destabilization KBMs at high . results compared with a generic tokamak case. We show that, large pressure gradients, frequency evaluated...
The theory of kinetic ballooning modes (KBMs) in a magnetically confined toroidal plasma is studied analytically and numerically by means gyrokinetic simulations. A physics-based ordering for β (the ratio to magnetic pressure) with small asymptotic parameters found. This allows us derive several simplified limits previously known theories. We introduce variational approach which provides explicit dispersion relations terms integrals quadratic forms constructed from numerical eigenfunctions....
Sawtooth-like core electron temperature crashes have been observed in W7-X experiments with cyclotron current drive. We present nonlinear single-fluid magnetohydrodynamic simulations of this phenomenon using the newly developed stellarator modeling capability M3D-$C^1$ code. The near-axis drive gives rise to two $\iota=1$ resonances equilibrium rotational transform profile so that consecutive $(1,1)$ internal kink modes are seen simulations. A small-amplitude crash at inner resonance occurs...
To examine the robustness of designed 5% β-limit for high-performance operation in W7-X stellarator, we undertake nonlinear magnetohydrodynamic (MHD) simulations pressure-driven instabilities using M3D-C 1 code.Consistent with linear analyses, ideal ballooning occur as β exceeds standard configuration.Nonetheless, modes saturate nonlinearly at relatively low levels without triggering large-scale crashes, even though confinement degradation worsens increases.In contrast, an alternative...
The dynamics of large scale plasma instabilities can be strongly influenced by the mutual interaction with currents flowing in conducting vessel structures. Especially eddy caused time-varying magnetic perturbations and halo directly from into walls are important.
Abstract In the Wendelstein 7-X (W7-X) stellarator, vacuum rotational transform, ι , has a flat radial profile and does not cross any major rational resonance. Nevertheless, during plasma operation ‐profile can be strongly modified by electron cyclotron current drive in such way that resulting -profile passes through low-order values, this trigger magnetohydrodynamic (MHD) events. Indeed, W7-X plasmas are sometimes subject to repetitive collapses of core confinement, which observed...
Abstract Mitigation of runaway electrons (REs) by three-dimensional (3D) magnetic field perturbations is numerically investigated for the ITER 15 MA baseline D–T scenario, utilizing MARS-F code (Liu et al Phys. Plasmas 7 3681) with a drift orbit test particle tracing module. Considered are two types 3D fields: n = 3 ( toroidal mode number) resonant perturbation (RMP) utilized purpose controlling edge localized modes in ITER, and generated 1 magneto-hydrodynamic (MHD) instabilities...
The stability properties of kinetic ballooning modes are investigated for a number magnetic configurations the stellarator Wendelstein 7-X. In particular, we consider effects vacuum rotational transform, ${\raise.1pt-\kern-6pt\iota}$ , and mirror ratio. analysis sheds light on interplay between global magnetohydrodynamic configuration local gyrokinetic stability, is instrumental in design high- $\beta$ (the ratio to pressure) operation scenarios. it demonstrated that some 7-X have relatively...
Abstract In this work, the stepped pressure equilibrium code (SPEC) (Hudson et al 2012 Phys. Plasmas 19 112502), which computes equilibria of multi-region relaxed magnetohydrodynamic energy principle (MRxMHD), has been upgraded to determine MRxMHD stability in toroidal geometry. A theoretical formalism for SPEC is obtained by relating second variation functional Hessian matrix, enabling prediction (MHD) linear instabilities. Negative eigenvalues matrix imply instability. Further, we...
Kinetic ballooning modes in magnetically confined toroidal plasmas are investigated putting emphasis on specific stellarator features. In particular, we propose a Mercier criterion which is purposely designed to allow for direct comparison with local flux-tube gyrokinetics simulations. We investigate the influence marginal frequency of mode magnetic curvature inhomogeneous flux surface due fieldline-label dependence. This typical (surface) global effect present non-axisymmetry. Finally, an...
An important question for the outlook of stellarator reactors is their robustness against pressure driven modes, and underlying mechanism behind experimentally observed soft $\beta$ limits. Towards building a robust answer to these questions, simulation studies are presented using recently derived reduced nonlinear MHD model. First, initial model implementation extended capture fluid compression by including influence parallel flows. Linear benchmarks (2, 1) tearing mode in W7-AS geometry,...
To examine the robustness of designed 5% $\beta$-limit for high-performance operation in W7-X stellarator, we undertake nonlinear magnetohydrodynamic (MHD) simulations pressure-driven instabilities using M3D-$C^1$ code. Consistent with linear analyses, ideal ballooning occur as $\beta$ exceeds standard configuration. Nonetheless, modes saturate nonlinearly at relatively low levels without triggering large-scale crashes, even though confinement degradation worsens increases. In contrast, an...