S. Bozhenkov
A5026228739- Magnetic confinement fusion research
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Geomagnetism and Paleomagnetism Studies
- Calibration and Measurement Techniques
- Stellar, planetary, and galactic studies
- Inorganic Fluorides and Related Compounds
- Particle Accelerators and Free-Electron Lasers
- Gas Dynamics and Kinetic Theory
- Laser Design and Applications
- Dust and Plasma Wave Phenomena
- Fluid Dynamics and Turbulent Flows
- X-ray Spectroscopy and Fluorescence Analysis
Max Planck Institute for Plasma Physics - Greifswald
2015-2024
Max Planck Institute for Plasma Physics
2013-2022
Max Planck Society
2012-2021
National Institute for Fusion Science
2016-2018
Princeton Plasma Physics Laboratory
2016-2018
The Graduate University for Advanced Studies, SOKENDAI
2018
Auburn University
2018
University of Maryland, College Park
2018
Australian National University
2016
Oak Ridge National Laboratory
2016
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...
Disruption mitigation is mandatory for ITER in order to reduce forces, mitigate heat loads during the thermal quench and avoid runaway electrons (REs). A fast disruption valve has been installed at JET study by massive gas injection. Different species amounts have investigated with respect timescales efficiency. We discuss of halo currents as well sideways forces vertical displacement events, increased energy dissipation through radiation, which could arise asymmetric radiation suppression REs.
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,...
The optimized, superconducting stellarator Wendelstein 7-X went into operation and delivered first measurement data after 15 years of construction one year commissioning. Errors in the magnet assembly were confirmend to be small. Plasma was started with 5 MW electron cyclotron resonance heating (ECRH) power five inboard limiters. Core plasma values keV, keV at line-integrated densities achieved, exceeding original expectations by about a factor two. Indications for core-electron-root found....
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...
This paper describes the design of Thomson scattering system at Wendelstein 7-X stellarator. For first operation campaign we installed a 10 spatial channel to cover radial half profile plasma cross section. The start-up is based on one Nd:YAG laser with Hz repetition frequency, observation optics, five fiber bundles delay line each, and interference filter polychromators spectral channels silicon avalanche diodes as detectors. High dynamic range analog digital converters 14 bit, 1 GS/s are...
Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future power plant. Plasma operation started in 2015 using limiter configuration. After installing an uncooled magnetic island divertor, extending energy limit from 4 80 MJ, continued 2017. For this phase, electron cyclotron resonance heating (ECRH) capability was extended 7 MW, and hydrogen pellet injection implemented. The enhancements resulted highest triple...
Wendelstein 7-X is a highly optimized stellarator that went into operation in 2015. With 30 cubic meter volume, superconducting coil system operating at 2.5 T, and steady-state heating capability of eventually up to 10 MW, it was built demonstrate the benefits stellarators parameters approaching those fusion power plant. We report here on first results with test divertor installed, during second phase, which performed half 2017. Operation divertor, addition several new fueling systems,...
A significant improvement of plasma parameters in the optimized stellarator W7-X is found after injections frozen hydrogen pellets. The ion temperature post-pellet phase exceeds 3 keV with 5 MW electron heating and global energy confinement time surpasses empirical ISS04-scaling. realized such experiments are significantly above those comparable gas-fuelled discharges. In this paper, we present details these pellet discuss main properties during enhanced phases. Local power balance applied...
The generation of runaway electrons in the international fusion experiment ITER disruptions can lead to severe damage at plasma facing components. Massive gas injection might inhibit process, but amount needed affect, e.g., vacuum systems. Alternatively, magnetic perturbations suppress by increasing loss rate. In TEXTOR losses were enhanced application resonant with toroidal mode number n=1 and n=2. are initiated fast about 3x10{21} argon atoms, which leads a reliable electrons. At...
The next step in the Wendelstein stellarator line is large superconducting device 7-X, currently under construction Greifswald, Germany. Steady-state operation an intrinsic feature of stellarators, and one key element 7-X mission to demonstrate steady-state plasma conditions relevant for a fusion power plant. device, on hand, requires implementation special technologies, giving rise technical challenges during design, fabrication assembly such device. On other also physics development at...
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 this were conducted with five graphite limiters as primary plasma-facing components. Overall, results beyond expectations published shortly before start [Sunn Pedersen et al., Nucl. Fusion 55, 126001 (2015)] both respect to parameters reached and themes addressed. We report here some most important plasma experiments that...
Wendelstein 7-X (W7-X) is currently under commissioning in preparation for its initial plasma operation phase, phase 1.1 (OP1.1). This first serves primarily to provide an integral of all major systems needed operation, as well systems, such diagnostics, that need verify their foreseen functions. In OP1.1, W7-X will have a reduced set in-vessel components. particular, five graphite limiter stripes replace the later divertor. paper describes expected machine capabilities selection physics...
The optimized stellarator Wendelstein 7-X started operation in December 2015 with a 10 week limiter campaign. Divertor experiments will begin the second half of 2017. W7-X Thomson scattering system is an essential diagnostic for electron density and temperature profiles. In this paper described detail, including its design, calibration, data evaluation first experimental results. Plans further development are also presented. Nd:YAG setup up to five lasers, two sets light collection lenses...
Abstract The fundamental behavior of the W7-X island divertor under detached conditions, which has been theoretically predicted with EMC3-Eirene code, is re-examined here experimental conditions achieved so far and compared first results. Both simulations experiments cover a range configurations plasma parameters, show following common trends: (1) rising impurity radiation, target heat load decreases ‘uniformly’ over entire surface in sense that both peak average loads can drop by an order...
The neoclassical transport optimization of the Wendelstein 7-X stellarator has not resulted in predicted high energy confinement gas fueled electron-cyclotron-resonance-heated (ECRH) plasmas as modelled (Turkin et al 2011 Phys. Plasmas 18 022505) due to levels turbulent heat observed experiments. electron-turbulent-heat appears non-stiff and is electron temperature gradient (ETG)/ion (ITG) type (Weir 2021 Nucl. Fusion 61 056001). As a result, Te can be varied freely from 1 keV–10 keV within...
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...
Abstract Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, performance quasi-continuous operation. Therefore, in recent campaign, experiments were performed prepare for long pulse operation, addressing three critical issues: development of stable detachment, control heat and particle exhaust, impact leading edges on plasma performance. The exhaust W7-X realized with help an island divertor, which utilizes large magnetic islands at boundary. This...
Runaway electrons represent a serious problem for the reliable operation of future experimental tokamak ITER.Due to multiplication factor exp(50) in avalanche even few seed runaway will result beam high energetic that is able damage machine.Thus suppression task importance, which reason we present here systematic study following massive gas injection TEXTOR.Argon can cause generation runaways carrying up 30% initial plasma current, while disruptions triggered by helium or mixtures argon (5,...
For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising method even for the envisaged application in fusion power plant. Wendelstein 7-X (W7-X) equipped with steady-state capable ECRH system, operating at 140 GHz, corresponds to 2nd cyclotron harmonic electrons magnetic field 2.5 T. Ten gyrotrons are operational and already delivered 7 MW W7-X plasmas. Combined pellet injection, highest triple product (0.68 × 1020 keV...
The Wendelstein 7-X (W7-X) optimized stellarator fusion experiment, which went into operation in 2015, has been operating since 2017 with an un-cooled modular graphite divertor. This allowed first divertor physics studies to be performed at pulse energies up 80 MJ, as opposed 4 MJ the phase, where five inboard limiters were installed instead of a This, and number other upgrades device capabilities, extension regimes higher plasma density, heating power, performance overall, e.g. setting new...