R. C. Wolf
A5067615849- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Atomic and Molecular Physics
- Nuclear reactor physics and engineering
- Gyrotron and Vacuum Electronics Research
- Astronomical Observations and Instrumentation
- Atomic and Subatomic Physics Research
- Calibration and Measurement Techniques
- Spacecraft and Cryogenic Technologies
- X-ray Spectroscopy and Fluorescence Analysis
- Scientific Measurement and Uncertainty Evaluation
- Inorganic Fluorides and Related Compounds
- Laser Design and Applications
- Particle Detector Development and Performance
- Astro and Planetary Science
- Particle Accelerators and Free-Electron Lasers
- Quantum Chromodynamics and Particle Interactions
Max Planck Institute for Plasma Physics
2014-2024
Max Planck Institute for Plasma Physics - Greifswald
2015-2024
Technische Universität Berlin
2017-2024
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
Max Planck Innovation
2002-2017
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...
Internal transport barriers in tokamak plasmas are explored order to improve confinement and stability beyond the reference scenario, used for ITER extrapolation, achieve higher bootstrap current fractions as an essential part of non-inductive drive. produced by modifications profile using external heating drive effects, often combined with partial freezing initial skin profile. Thus, formerly inaccessible ion temperatures QDTeq values have been (transiently) achieved. The present paper...
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,...
In this paper the manipulation of power deposition on divertor targets at DIII-D by application resonant magnetic perturbations (RMPs) for suppression large type-I edge localized modes (ELMs) is analysed. We discuss modification ELM characteristics RMP applied. It shown that width pattern in ELMy H-mode depends linearly deposited energy, whereas phase discharge those patterns are controlled externally induced perturbation. was also found heat transport due to small, plasma pedestal electron...
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...
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...
This paper analyses the properties of a critical gradient transport model based on few assumptions: electrostatic gyroBohm scaling law, existence an instability threshold and finite background below threshold. A quantitative criterion stiffness is proposed, which provides means for assessment inter-machine comparison. It also shown that this compatible with two-term law global confinement, as proposed recently by International Tokamak Physics Activity–Confinement Data Base Modelling Topical...
A study of three-dimensional (3D) perturbed magnetic field structures and transport for edge localized mode control experiments with resonant perturbations at DIII-D is presented. We focus on ITER-Similar Shape plasmas ITER relevant electron pedestal collisionalities . This performed in comparison results from TEXTOR-Dynamic Ergodic Divertor circular limiter plasmas. For both the structure analyzed vacuum paradigm—superimposing external RMP unperturbed equilibrium. TEXTOR L-mode this...
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...
Interferometry as one of the most common core fusion diagnostics has traditionally suffered from incomplete vibration compensation. Dispersion interferometry promises a more complete compensation vibrations. For this reason it is being employed in an increasing number experiments. However, thus far none them have shown reliable real-time low-latency processing dispersion data. Nonetheless necessity for machines when trying to do density feedback control, notably long discharges like ones...
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...
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...
Stationary discharges with $H$-mode edge and internal transport barrier for energy, momentum, particle have been obtained on ASDEX Upgrade. At a line averaged density of $4\ifmmode\times\else\texttimes\fi{}{10}^{19}{\mathrm{m}}^{\ensuremath{-}3}$ an $H$ factor ${H}_{\mathrm{ITER}89\ensuremath{-}P}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.4$ ${\ensuremath{\beta}}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ could be maintained 6 s corresponding to 40 confinement times,...
A beam of injected fast atomic hydrogen presents a superb probe for hot fusion plasmas. The neutral particles experience excitation and ionization by collisions with electrons ions as they penetrate into plasma. emitted characteristic line radiation is Doppler shifted the spectral lines are split due to motional Stark fields. Measurements wavelength, intensity polarization Balmer- alpha emission reveal information about beam, such attenuation, beam-geometry, beam-divergence species mix....
The magnetic-field perturbation produced by the dynamic ergodic divertor in TEXTOR changes topology of magnetic field plasma edge, creating an open chaotic system. spectrum contains only a few dominant harmonics and therefore it can be described analytical model. modeling is performed vacuum approximation without assuming backreaction does not rely on any experimentally obtained parameters. It shown that this predicts many details observed structure. Several experiments have been to prove...
The dynamic ergodic divertor (DED) on the TEXTOR tokamak allows for creation of static and rotating helical magnetic perturbation fields. In 3/1 configuration strong m/n = 2/1 sideband excites a locked tearing mode above critical field strength. onset threshold depends strongly plasma fluid rotation with respect to mode. Rotation in current direction destabilizes certain range frequencies, whereas counter-rotation has stabilizing influence. shows minimum when frequency external equals MHD
At the TEXTOR tokamak an external resonant magnetic perturbation is applied with dynamic ergodic divertor to control edge transport properties. The approaches analyse impact of such a kind stochastization on apply mostly shell-like picture which includes dependence from field topology in radial direction only. In this paper multiple experimental evidence presented contrast these forms poloidally heterogenous layer characteristics are determined by alternating line behaviour. A thorough...
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,...