A5003281329- 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
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Physics of Superconductivity and Magnetism
- High voltage insulation and dielectric phenomena
- Magneto-Optical Properties and Applications
- Blind Source Separation Techniques
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Fault Detection and Control Systems
- Viral Infections and Vectors
- Optical Network Technologies
- Real-time simulation and control systems
- Intermetallics and Advanced Alloy Properties
- Electromagnetic Effects on Materials
- Vacuum and Plasma Arcs
- High-pressure geophysics and materials
- Gamma-ray bursts and supernovae
- High-Energy Particle Collisions Research
Max Planck Institute for Plasma Physics
2017-2025
Culham Centre for Fusion Energy
2024
Fusion (United States)
2022
Plasma Technology (United States)
2022
Fusion Academy
2022
Technical University of Munich
2018-2021
Max Planck Society
2017-2021
Université de Lorraine
2018
Centre National de la Recherche Scientifique
2018
Institut Jean Lamour
2018
Over previous campaigns, an intense experimental program on advanced tokamak (AT) scenarios, has been carried out at the ASDEX Upgrade with full-tungsten wall. These discharges have executed shortly after boronization of first wall to reduce density and impurity influx. The confinement level such AT was found vary considerably, even when similar, if not identical, engineering parameters were out. This work investigates causes variations. Among all plasma quantities analyzed, quality...
One of our grand challenges towards fusion energy is the achievement a high-performance plasma core coupled to boundary solution. The high confinement mode (H-mode) provides such due build-up an edge transport barrier leading pedestal. However, it usually features type-I localized modes (ELMs) which pose threat for long-duration operation in future devices as they induce large fluences onto facing components and typically are projected damage first wall. For devices, integration stationary...
Abstract The Low Frequency Edge Oscillation (LFEO) is a low frequency fluctuation in many plasma quantities the pedestal region of I-Mode confinement regime. It observed on Alcator C-Mod between 10-30kHz and ASDEX Upgrade 5-10kHz. On both tokamaks it has been previously identified as Geodesic Acoustic Mode (GAM), however recent discovery Temperature Ring (ETRO) similar spatial location LFEO I-Modes EAST called this identification into question. In paper we investigate AUG using variety...
Abstract Understanding the transport processes that determine plasma profile widths in scrape-off layer (SOL) and divertor region of tokamaks is crucial for successful power particle exhaust management future devices. Plasma from SOL into Private Flux Region (PFR) broadens profiles could mitigate challenge. Analysis ion current profiles, measured by Langmuir probes ASDEX Upgrade (AUG) tokamak, shows width PFR, normalized flux expansion between outer target midplane, about \SI{1.5}{mm} L-mode...
Abstract A cross-regime (L-mode, I-mode and H-mode) database combining scrape-off layer (SOL) power decay length λ q divertor measurements upstream SOL electron pressure, temperature density lengths has been assembled at ASDEX Upgrade. It is found that a scaling best described by local edge quantity, such as the pressure evaluated ρ pol = 0.95. Furthermore, exhibits clear correlation with gradient lengths, no matter if taken inside or outside separatrix. In addition, reveals pedestal...
The effect of triangularity on tokamak boundary plasma turbulence is investigated by using global, flux-driven, three-dimensional, two-fluid simulations. simulations show that negative stabilizes turbulence, and linear investigations reveal this due to a reduction the magnetic curvature drive interchange instabilities, such as resistive ballooning mode. As consequence, pressure decay length $L_p$, related SOL power fall-off $\lambda_q$, found be affected triangularity. Leveraging...
The I-mode is an attractive confinement regime for future tokamak based fusion reactors.A model presented which explains the by reduction of ITG turbulence near separatrix at low collisionality, where ion temperature can exceed electron temperature.Drift-Alfvénturbulence develops, with large and small-scale fluctuations being suppressed phase randomization finite-Larmor-radius effects, respectively.The intermediate scales form a broad peak in frequency spectrum, features same properties as...
The I-mode confinement regime is promising for future reactor operation due to high energy without particle confinement. However, the role of edge turbulence in creating I-mode's beneficial transport properties still unknown. New measurements (ρpol=0.9−1.0) L-modes and I-modes at low densities ASDEX Upgrade are presented this paper. A radial resolution correlation electron cyclotron emission radiometer measures broadband throughout L-mode pedestal. weakly coherent mode (WCM) measured both...
The I-mode confinement regime can feature small edge temperature drops that lead to an increase in the energy deposited onto divertor targets.In this work, we show these events are associated with a relaxation of both electron and density profiles, largest drop found at pedestal top position.The relative loss is about 1 %, thus lower than type-I ELMs for same collisionality.Stability analysis profiles reveals operational points far from ideal peeling-ballooning boundary.Also, appear close...
Recent I-mode investigations from the ASDEX Upgrade tokamak are reported. It is shown that neutral-beam-injection heated I-modes can be stationary, which important in terms of extrapolability towards future fusion devices. Furthermore, detailed studies on weakly coherent mode In particular, experimental observations point its existence L-mode, before starts. Moreover, impact density and temperature fluctuations evaluated. Studies stationary divertor heat fluxes show I-mode, upstream power...
The electric field in the Scrape-Off Layer (SOL) of fusion plasmas is a key quantity affecting local plasma transport and possibly also overall confinement. However, physics determining SOL experimentally not well investigated. In this study systematic experimental analysis AUG L-mode discharges at various currents, densities heating powers presented. particular, relation to divertor condition, as measured by Langmuir probes, analyzed detail applying simplified form Ohm's law. shows that...
In divertor tokamaks electric currents flowing in the Scrape-Off Layer (SOL) are a frequently observed and well known feature. However, convective heat flux carried by these is often assumed to be small compared total parallel flux. this paper it shown that ASDEX Upgrade current, which was measured Langmuir probes at outer target, can several times larger than ion saturation current low density L- H-mode discharges. Therefore they have taken into account when calculating target from probe...
The orbit-following Monte Carlo code ASCOT interfaced with the radiofrequency library RFOF can simulate heating of ion populations using wave solutions from full-wave solvers such as TORIC. It is applied to fundamental mode cyclotron resonant hydrogen and 2nd harmonic frequency neutral beam injected deuterium in ASDEX Upgrade discharge #33147 validate model against fast loss detector (FILD) measurements. In addition, for FILD signal simulations requiring enhanced resolution or scanning...
Plasma core fuelling is a key issue for the development of steady-state scenarios in large magnetically-confined fusion devices, particular helical-type machines. At present, cryogenic pellet injection most promising technique efficient fuelling. Here, ablation and efficiency experiments, using compact injector, are carried out electron cyclotron resonance neutral beam heated plasmas stellarator TJ-II. Ablation profiles reconstructed from light emissions collected by silicon photodiodes...
Abstract One of the major challenges for design future thermonuclear reactors is problem power exhaust—the removal heat fluxes deposited by plasma particles onto plasma-facing components (PFCs) reactor wall. In order to work efficiently, loading PFCs has stay within their material limits. A substantial part these can be transiently during impact edge localised modes (ELMs), which typically accompany high confinement mode, a regime foreseen tokamak ITER and next-step devices. possible ways...
We compare various diagnostics characterizing an ASDEX Upgrade upper single-null discharge to EMC3-EIRENE simulations now including volumetric recombination and main chamber plasma-wall interaction but not yet drifts. The is in a small-ELM regime approaching detachment due density ramp nitrogen seeding. Time/ELM averaged upstream density, electron ion temperature measurements as well downstream saturation current, power flux match the simulation within error bars before after reaching...
In some conditions, I-mode plasmas can feature pedestal relaxation events (PREs) that transiently enhance the energy reaching divertor target plates. To shed light into their appearance, characteristics and targets, a comparative study between two tokamaks $-$ Alcator C-Mod ASDEX Upgrade is carried out. It found PREs appear only in subset of discharges, mainly when plasma close to H-mode transition. Also, nature triggering instability discussed by comparing measurements separatrix both...
Abstract Experiments on nitrogen assisted divertor detachment in the improved energy confinement mode (I-mode) are reported from ASDEX Upgrade tokamak. When is introduced into and radiation losses cool plasma down, a loss of core observed, concomitant with an increase low frequency edge fluctuation levels. The can be compensated I-mode maintained by additional heating power input. Detachment inner leg has been observed for first time discharge. outer remains attached these experiments. Good...
Abstract This letter reports on the efforts carried out at ASDEX Upgrade tokamak to integrate I-mode plasmas with pellet fueling and increase Greenwald fraction <?CDATA $f_{\mathrm{GW}}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>f</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">G</mml:mi> mathvariant="normal">W</mml:mi> </mml:mrow> </mml:msub> </mml:math> , two important requirements for any DEMO operational scenario. For first time,...
Abstract The I-mode confinement regime in non-deuterium plasmas has been investigated the ASDEX Upgrade tokamak. We report first experimental observations on existence and main characteristics of this hydrogen helium compare them with deuterium I-modes. Hydrogen features a higher power threshold to enter electron edge pressure at L- transition respect deuterium. Furthermore, all I-modes obtained exhibit pedestal relaxation events (PRE). window is found be 2–3 times larger than This property...
ASDEX Upgrade is preparing a hardware modification of its upper divertor in order to study alternative configurations, like the X-divertor (XD) and snowflake (SF), that are discussed as possible solution for power exhaust problem. Experiments characterizing current single-null (SN) configuration before during detachment were carried out recently interpreted by EMC3-EIRENE (Lunt et al., 2020) now including volumetric recombination. In continuation these studies we here report on further...
Abstract SOLPS‐ITER L‐mode‐like simulations with the full set of currents and drift velocities activated, fluid neutrals have been carried out to interpret experimental results obtained in AUG. Drifts are critical quantitatively reproduce results; however, without drifts can also some trends qualitatively. The magnitude dependence peak heat flux onto both targets on upstream collisionality are, general, quantitative agreement within uncertainties infrared thermography measurements favourable...
Pairs of ASDEX Upgrade L-mode discharges with the toroidal magnetic field, BT, in forward and reverse directions have been used to study impact neoclassical drifts on divertor plasma conditions detachment. The evolution peak heat flux total power loads onto both outer inner targets depends significantly field direction: increasing core density affects mainly BT < 0 (unfavourable) direction, whereas current has a larger for > (favourable). Ion saturation measurements show similar trends those...
The I-mode is an edge-localized mode (ELM)-free confinement regime showing enhanced heat confinement. Nevertheless, also in I-mode, events similar to ELMs—albeit less harmful the divertor—can occur, relaxing pedestal gradients. A global electromagnetic gyrofluid simulation of such a relaxation event (PRE) conditions presented and qualitatively compared with previous measurements PREs ASDEX Upgrade [Silvagni et al., Nucl. Fusion 60, 126028 (2020)]. shows precursor-oscillation characteristic...