A5034261268- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-induced spectroscopy and plasma
- Fluid Dynamics and Turbulent Flows
- Particle Accelerators and Free-Electron Lasers
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Dust and Plasma Wave Phenomena
- Geomagnetism and Paleomagnetism Studies
- Magnetic Field Sensors Techniques
- Laser Design and Applications
- Electrostatic Discharge in Electronics
- Metal and Thin Film Mechanics
- X-ray Spectroscopy and Fluorescence Analysis
- Meteorological Phenomena and Simulations
- Advanced MRI Techniques and Applications
- Magnetic Properties of Alloys
- Adaptive optics and wavefront sensing
- Nuclear reactor physics and engineering
Max Planck Institute for Plasma Physics - Greifswald
2015-2024
Technical University of Denmark
2018-2024
European Organization for Nuclear Research
2016-2023
Max Planck Institute for Plasma Physics
2013-2022
Campbell Collaboration
2020-2022
Max Planck Society
2012-2021
Princeton Plasma Physics Laboratory
2016-2021
HUN-REN Centre for Energy Research
2021
Google (United States)
2019
Huazhong University of Science and Technology
2018
This paper reviews measurements of edge plasma turbulence in toroidal magnetic fusion devices with an emphasis on recent results tokamaks. The dominant feature is a high level broadband density fluctuations relative amplitude δn/n ∼ 5–100%, accompanied by large potential and electron temperature fluctuations. frequency range this ∼10 kHz–1 MHz, the size scale typically ∼0.1–10 cm perpendicular to field but many metres along field, i.e. structure nearly that 2D 'filaments'. Large intermittent...
High energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. In order to increase or reduce size accelerator, new acceleration schemes need be developed. Plasma wakefield acceleration, which electrons plasma are excited, leading strong electric fields, is one such promising novel technique. Pioneering experiments shown an intense laser pulse electron bunch traversing plasma, drives fields 10s...
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...
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...
The object of this review is to summarize the achievements research on Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] place that in context quest for practical fusion energy. a compact, high-field tokamak, whose unique design operating parameters have produced wealth new important results since it began operation 1993, contributing data extends tests critical physical models into parameter ranges regimes. Using only...
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...
The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment CERN the world׳s first experiment. AWAKE will be installed in former CNGS facility uses 400 GeV/c beam bunches from SPS. experiments focus on self-modulation instability of long (rms ~12 cm) bunch plasma. These are planned for end 2016. Later, 2017/2018, low energy (~15 MeV)...
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...
Radially propagating spatiotemporal fluctuation structures are observed in the scrape-off layer of Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, (1994)] using combination electric probes, a radial array views measuring Dα emission, and two-dimensional imaging emission. For specific magnetic-field configuration probe measured plasma density potential fluctuations along same magnetic-flux tube. Calculations cross-correlation functions intensity with ion saturation current floating...
New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach to exploit properties plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or electron bunch into plasma. However, maximum energy gain electrons accelerated in a single stage limited driver. Proton bunches are most drivers wakefields accelerate TeV scale stage. An experimental program at CERN—the...
We give direct experimental evidence for the observation of full transverse self-modulation a long, relativistic proton bunch propagating through dense plasma. The exits plasma with periodic density modulation resulting from radial wakefield effects. show that is seeded by ionization front created using an intense laser pulse copropagating bunch. extends over length following seed point. By varying one order magnitude, we frequency scales expected dependence on density, i.e., it equal to...
The seeded self-modulation of a relativistic, charged particle bunch in plasma is shown to grow both along the and plasma, resulting transverse wakefield amplitudes that far exceed initial seed values.
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...
We show in experiments that a long, underdense, relativistic proton bunch propagating plasma undergoes the oblique instability, which we observe as filamentation. determine threshold value for ratio between transverse size and skin depth instability to occur. At threshold, outcome of experiment alternates filamentation self-modulation (evidenced by longitudinal modulation into microbunches). Time-resolved images density distribution reveal grows an observable level late along bunch,...
AWAKE is a proton-driven plasma wakefield acceleration experiment. % We show that the experimental setup briefly described here ready for systematic study of seeded self-modulation 400\,GeV proton bunch in 10\,m-long rubidium with density adjustable from 1 to 10$\times10^{14}$\,cm$^{-3}$. short laser pulse used ionization vapor propagates all way along column, suggesting full vapor. occurs bunch, at time and follows affects bunch.
The investigation of edge plasmas at the stellarator W7-X requires a flexible tool for integration variety different diagnostics as e.g. electrical probes, probing magnetic coils, material collection, or exposition and gas injection. A multi-purpose manipulator (MPM) system has been developed attached to vessel before operational phase 1.1. was designed user facility many diagnostics, which can be mounted on unique interface without breaking vacuum. system, located in equatorial plane,...
The transport of heavy impurities has been investigated at the Wendelstein 7-X stellarator during core electron root confinement (CERC) experiments. Iron atoms were injected via laser blow-off technique and analyzed by VUV x-ray spectrometers. amount iron does not change global plasma parameters but yields strong enough line radiation for detailed studies based on impurity code STRAHL. latter is supplied with neo-classical diffusion convection profiles from drift kinetic equation solver...
Abstract Classical particle drifts are known to have substantial impacts on fluxes of particles and heat through the edge plasmas in both tokamaks stellarators. Here we present results from first dedicated investigation drift effects W7-X stellarator. By comparing similar plasma discharges conducted with a forward- reverse-directed magnetic field, could be isolated observation up-down asymmetries flux profiles divertor targets. In low-density plasmas, radial locations strike lines (i.e....
Abstract We demonstrate favorable stability properties of maximum- J stellarators, exemplified by the Wendelstein 7-X (W7-X) device, in scenarios with low plasma beta. A large number electrostatic linear gyrokinetic simulations are conducted to scan relevant parameter space for different configurations, resulting maps that account key micro-instabilities thought drive turbulent transport. These exhibit a ‘stability valley’ region where normalized ion temperature gradient is roughly equal...
Pulsed injections of boron carbide granules into Wendelstein 7-X stellarator (W7-X) plasmas transiently increase the plasma stored energy and core ion temperatures above reference W7-X experimental programs by up to 30%. In a series 4 MW electron cyclotron resonance heating experiments, PPPL Probe Mounted Powder Injector provided 50 ms bursts 100 μm every 350 at estimated quantities ranging from approximately 1 mg/pulse over 30 mg/pulse. For each injection, was observed initially drop...
Plasma wakefield acceleration is a promising technology to reduce the size of particle accelerators. The use high energy protons drive wakefields in plasma has been demonstrated during Run 1 AWAKE programme at CERN. Protons 400 GeV drove that accelerated electrons 2 under 10 m plasma. collaboration now embarking on with main aims demonstrate stable accelerating gradients 0.5–1 GV/m, preserve emittance electron bunches and develop sources scalable 100s metres beyond. By end 2, scheme should...
Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven short, misaligned preceding bunch. Hosing develops the plane misalignment, self-modulation perpendicular plane, at frequencies close to electron frequency, and are reproducible. Development depends on misalignment direction, its growth extent proton charge. Results have main characteristics theoretical model, relevant other plasma-based accelerators represent first characterization...