A5025068207- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Gas Dynamics and Kinetic Theory
- Chemical Thermodynamics and Molecular Structure
- Scientific Measurement and Uncertainty Evaluation
- Atomic and Subatomic Physics Research
- Geophysics and Gravity Measurements
- High-pressure geophysics and materials
- Advanced Frequency and Time Standards
- Thermal and Kinetic Analysis
- Molecular Spectroscopy and Structure
Max Planck Institute for Plasma Physics - Greifswald
2015-2024
Max Planck Institute for Plasma Physics
2005-2021
Max Planck Society
2007-2021
Max Planck Innovation
1993-2017
Australian National University
2016
Oak Ridge National Laboratory
2016
Physikalisch-Technische Bundesanstalt
2016
University of Opole
2016
CEA Cadarache
2016
National Institute for Fusion Science
2016
A comprehensive investigation has been performed of the static and dynamic behaviour detached recombining plasmas in linear divertor plasma simulator NAGDIS-II. For stationary detachment, transition from electron-ion recombination (EIR) to molecular activated (MAR) observed by injecting hydrogen gas into high density helium plasmas. The particle loss rate due MAR is found be comparable that EIR. Experiments have also injection a heat pulse produced RF heating demonstrate volumetric...
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,...
Several experiments were conducted in ASDEX Upgrade to prove the suitability of tungsten as a divertor target material under conditions high density and low temperature divertor. The observed fluxes from tile into plasma are low, keeping with extremely sputtering yields. In addition, very favourable effect `prompt redeposition' (redeposition during first gyration) could be confirmed by experiments. Cooling edge region neon injection seems permissible, i.e. impurity did not increase eroded...
A promising new plasma operational regime on the Wendelstein stellarator W7-AS has been discovered. It is extant above a threshold density and characterized by flat profiles, high energy low impurity confinement times, edge-localized radiation. Impurity accumulation avoided. Quasistationary discharges with line-averaged densities n(e) to 4 x 10(20) m(-3), radiation levels 90%, partial detachment at divertor target plates can be simultaneously realized. Energy up twice that of standard...
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...
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...
W7-AS has recently been equipped with ten open divertor modules in order to experimentally evaluate the island concept. First results are reported this paper. The new divertors enable access a NBI-heated, very high density (up e = 3.5 × 1020 m-3) operating regime promising confinement properties. energy time increases steeply and then saturates. In contrast, particle impurity times decrease increasing density. This allows full control quasi-steady-state operation also under conditions of...
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...
The completely detached high confinement (CDH) regime established recently in power ASDEX-Upgrade single null divertor discharges is described. standard CDH mode scenario with feedback controlled external deuterium and neon puffing analysed detail respect to its detachment properties. Impurity transport pumping effects the density operation windows of are outlined. First results other impurity radiators (N,Ar) given. Finally space discussed terms main chamber scrape-off layer plus radiation...
Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters December 2015. At end of 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were operation, allowing detailed studies many interesting plasma phenomena. For example, fast neutral gas manometers supported video cameras (including one fast-frame camera frame rates...
Tungsten erosion in the ASDEX Upgrade divertor has been measured by observing WI emission at 400.9 nm. The sputtering yield is region of atoms/ion for typical plasma conditions. By comparison with modelled yields one can conclude that tungsten dominated impurities. Adding impurities without cooling boundary increases due to additional impact energy gained particle sheath potential caused its higher net charge. Cooling adding more or increasing density leads a strong decrease erosion. influx...
Wendelstein 7-X (W7-X) is a large optimized stellarator (B=2.5T, V=30m3) aiming at demonstrating the reactor relevance of stellarators. In 2015 W7-X will begin its first operation phase (OP1.1) with five inertially cooled inboard limiters made graphite. Assuming heat loads can be spread out evenly between limiters, 1 second discharges 2 MW ECRH heating power could run in OP1.1. The expected plasma parameters sufficient to demonstrate readiness installed diagnostics and even physics program....
This paper assesses the three-dimensional (3D) effects of edge magnetic field structure on divertor/scrape-off layer transport, based an inter-machine comparison experimental data and recent progress 3D transport simulation. The are elucidated as a consequence competition between transports parallel () perpendicular to field, in open lines cut by divertor plates, or islands. has strong impacts functions, such determination density regime, impurity screening detachment control. perturbation...
This paper presents a detailed analysis of the transport behaviour detached plasmas in W7-AS based on an extended numerical study using EMC3-EIRENE code, aimed at understanding underlying physics responsible for geometry-dependent detachment stability observed island divertor experiments. Here, stable can only be established when control coils are switched to generate sufficiently large islands with relatively short connection lengths. Special attention will paid discussion carbon radiation,...
Abstract In the Large Helical Device (LHD) a low temperature mode (LTM) of helical divertor was discovered. It combines particle detachment and very large sub-divertor pressures up to 1.4 Pa. During LTM, electron in range from 0.25 0.42 eV so that volume recombination occurred. This result is remarkable because stellarators LHD Wendelstein 7-X only (0.03–0.3 Pa) were expected measured now due loss pressure conservation along flux tubes by an enhanced cross-field transport. demonstrates more...
High density operation in the ASDEX Upgrade divertor I with horizontal target plates is reported. Density rampup experiments were carried out to characterize detached plasma conditions divertor. During phases, hydrogen continua and spectral line emission from high-n shells observed due volume recombination. The spectroscopic measurements provide a consistent picture of evolution parameters during ramp. By means ADAS atomic physics program package, rate recombination was evaluated, including...
In the ASDEX Upgrade, X-point marfe formation and its behaviour up to density limit is investigated in gas-fuelled ohmically-heated single-null discharges over a wide range of parameters: Ip=0.6-1.2 MA, BTF=1.35-2.4 T, plasma elongation 1.6 Zeff<2. The standard-ion Del B drift directed towards X-point. At medium electron densities inevitably develops vicinity active consistent with model thermal instabilities radiating edge plasma. Moreover, stable steady-state operation demonstrated marfes...
Recombination in a helium and helium-hydrogen plasma was experimentally investigated the linear divertor simulator NAGDIS-II. To identify physical mechanisms, electron-ion recombination (EIR) molecular assisted (MAR), parameters recombining region have been measured. We used spectroscopic techniques on basis of continuum emission line from highly excited levels due to EIR Langmuir probes. The dependence neutral pressure pure mixture shows clearly that is caused by different processes two...
Using the island divertors (IDs) of W7-AS and W7-X helical divertor (HD) LHD as examples, paper presents a comparative transport study for three typical devices different machine sizes following two distinct concepts, aiming at identifying common physics issues/effects mutual validation combined studies. Based on EMC3/EIRENE simulations supported by experimental results, first reviews compares essential features ID HD in order to build base framework predictive W7-X. The fundamental role...
To improve the reliability of ASDEX pressure gauges in plasma vessel Wendelstein 7-X stellarator, nine them were equipped with a LaB6 crystal electron emitter for first time. These cathode operated during last campaign 2018 (operation phase 1.2b) only 2 A heating current over 40 h magnetic field about 2.1 T without failure. Owing to this excellent performance, we have decided equip all cathodes next 2). We report on pretest superconducting magnet, show measurement neutral 7-X, and...
Abstract During the first test divertor campaign of stellarator experiment Wendelstein 7-X (Pedersen et al 2022 Nucl. Fusion 62 042022), OP1.2b, 13 neutral gas pressure gauges collected data in different locations plasma vessel, enabling a detailed analysis pressures, compression ratios and particle exhaust rates via turbomolecular pumps magnetic field configurations. In 7-X, edge islands are intersected by target plates used to create plasma-wall interface. As number position varies...
In 1997 the new `LYRA' divertor went into operation at ASDEX Upgrade and, in parallel, neutral beam heating power was increased to 20 MW by installation of a second injector leading P/R value 12 MW/m. Experiments have shown that LYRA is capable handling such high powers. There an overall reduction maximum heat flux about factor 2 compared with previous open Div I. This mainly due radiative losses inside region, which are caused effective reflection hydrogen neutrals hot separatrix region....