K. Krieger
A5086088247- Magnetic confinement fusion research
- Fusion materials and technologies
- Nuclear Materials and Properties
- Superconducting Materials and Applications
- Nuclear reactor physics and engineering
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Nuclear Physics and Applications
- Ion-surface interactions and analysis
- Metallurgical Processes and Thermodynamics
- Metal and Thin Film Mechanics
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Muon and positron interactions and applications
- Diamond and Carbon-based Materials Research
- Non-Destructive Testing Techniques
- Advanced Sensor Technologies Research
- Radioactive contamination and transfer
- Silicon and Solar Cell Technologies
- Spacecraft and Cryogenic Technologies
- High voltage insulation and dielectric phenomena
- Cold Fusion and Nuclear Reactions
- Dust and Plasma Wave Phenomena
Max Planck Institute for Plasma Physics
2016-2025
Culham Centre for Fusion Energy
2024
Dutch Institute for Fundamental Energy Research
2023
Helmholtz-Zentrum Dresden-Rossendorf
2023
Universitätsmedizin Greifswald
2022
Max Planck Society
2012-2021
Royal Military Academy
2020
Max Planck Innovation
1988-2017
Forschungszentrum Jülich
2017
Culham Science Centre
2013-2016
Progress, since the ITER Physics Basis publication (ITER Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding processes that will determine properties of plasma edge and its interaction with material elements is described. Experimental areas where significant progress has taken place are energy transport scrape-off layer (SOL) particular anomalous scaling, particle SOL plays a major role diverted plasmas main-chamber elements, localized mode (ELM) deposition on mechanism for ELM...
JET underwent a transformation from full carbon-dominated tokamak to fully metallic device with beryllium in the main chamber and tungsten divertor. This material combination is foreseen for activated phase of ITER. The ITER-Like Wall (ILW) experiment at shall demonstrate plasma compatibility walls reduction fuel retention. We report on set experiments (Ip = 2.0 MA, Bt 2.0–2.4 T, δ 0.2–0.4) different confinement conditions global gas balance analysis demonstrating strong long-term retention...
Recent research in scrape-off layer (SOL) and divertor physics is reviewed; new existing data from a variety of experiments have been used to make cross-experiment comparisons with implications for further ITER. Studies the region near separatrix addressed relationship profiles turbulence as well scaling parallel power flow. Enhanced low-field side radial transport implicated driving flows inboard side. The medium-n nature edge localized modes (ELMs) has elucidated measurements determined...
The key remaining physics design issue for the ITER tungsten (W) divertor is question of monoblock (MB) front surface shaping in high heat flux target areas actively cooled targets. Engineering tolerance specifications impose a challenging maximum radial step between toroidally adjacent MBs 0.3 mm. Assuming optical projection parallel loads, magnetic shadowing these edges required if quasi-steady state melting to be avoided under certain conditions during burning plasma operation and...
Abstract The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and preparation operation, as well addressing issues for a future DEMO design. Since 2015, AUG equipped with new pair 3-strap ICRF antennas, which were designed reduction tungsten release during operation. As predicted, factor two on ICRF-induced W plasma content could be achieved by sheath voltage at antenna limiters via compensation image currents central side straps in...
The original goals of the JET ITER-like wall included study impact an all W divertor on plasma operation (Coenen et al 2013 Nucl. Fusion 53 073043) and fuel retention (Brezinsek 083023). ITER has recently decided to install a full-tungsten (W) from start operations. One key inputs required in support this decision was possibility melting melt splashing during transients. Damage type can lead modifications surface topology which could higher disruption frequency or compromise subsequent...
JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation long-term fuel retention. The (i) limiter and (ii) divertor configurations have been studied JET-ILW (JET Be first wall W divertor), compared those former JET-C carbon-based plasma-facing (PFCs)). For configuration, gross at contact point was determined situ by spectroscopy between 4% (Ein = 35 eV) more than 100%, caused...
Abstract In future fusion reactors, extended melt pools in combination with strong plasma-induced accelerations, suggest that the metallic could reach gaps between castellated plasma-facing components, potentially accompanied by profound changes their mechanical response. The first results of a combined experimental and modelling effort to elucidate physics transport across are presented. Transient melting specially designed tungsten samples featuring toroidal has been achieved ASDEX Upgrade...
Abstract Since the publication of review Progress in ITER Physics Basis (PIPB) 2007, significant progress has been made understanding processes at plasma-material interface. This review, part ITPA Nuclear Fusion Special Issue On Path to Burning Plasma Operation , presents these developments, focusing on key areas such as physics plasma exhaust, interactions, and properties plasma-facing materials their evolution under exposure. The coordinated efforts Topical Group Scrape-Off Layer Divertor...
Feedback-controlled puffing of neon and deuterium has been applied to control the edge-localized-mode behavior target plate power deposition during high-power $H$-mode discharges in ASDEX Upgrade. A regime found which more than 90% heating is lost through radiation divertor detachment occurs, without deterioration energy confinement. The plasma remains $H$ mode, exhibiting small-amplitude, high-frequency ELM's, do not penetrate plates strike zone region.
The unsaturated linear rise of the energy confinement time with density, ${\ensuremath{\tau}}_{E}\ensuremath{\sim}{\overline{n}}_{e}$, up to density limit is recovered in Ohmically heated discharges ASDEX. Improvement a factor 2 reached ${\ensuremath{\tau}}_{E}\ensuremath{\approx}150$ ms at ${\overline{n}}_{e}=5\ifmmode\times\else\texttimes\fi{}{10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ improved state characterized by peaked profiles. ion heat diffusivity decreases neoclassical value....
ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It found that large He content in plasma, resulting from DC glow discharges for conditioning, leads a confinement reduction. After change D inter-shot quickly dropped and, parallel, usual H-Mode with H factors close one achieved. initial conditioning phase, oxygen concentrations...
The issue of first wall and divertor target lifetime represents one the greatest challenges facing successful demonstration integrated tokamak burning plasma operation, even in case planned next step device, ITER, which will run at a relatively low duty cycle comparison to future fusion power plants. Material erosion by continuous or transient ion neutral impact, susbsequent transport released impurities through their deposition and/or eventual re-erosion constitute process migration. Its...
The migration of first wall material due to erosion, plasma transport and re-deposition is one the key challenges in current future fusion devices.To predict erosion/re-deposition patterns understand underlying principal processes, global simulation code WallDYN was developed.It couples evolution surface composition impurity transport.To benchmark model, it applied JET ITER-Like Wall experiment (JET-ILW), which mimics ITER configuration thus an ideal environment validate predictive...
Abstract The paper reports the first demonstration of in situ laser-induced desorption — quadrupole mass spectrometry (LID-QMS) application on a large scale fusion device performed summer 2023. LID-QMS allows direct measurements fuel inventory plasma facing components without retrieving them from device. diagnostic desorbs retained gases by heating 3 mm diameter spot wall using 1 ms long laser pulse and detects QMS. Thus, it can measure gas content at any position accessible to laser....
At the central column of ASDEX Upgrade, an area 5.5 m2 graphite tiles was replaced by tungsten-coated representing about two-thirds total column. No negative influence on plasma performance found, except for internal transport barrier limiter discharges. The tungsten influx ΓW stayed below detection limit only during direct wall contact or reduced clearance in divertor discharges spectroscopic evidence could be found. From these observations a penetration factor order 1% and effective...
Recent experiments at ASDEX Upgrade have achieved advanced scenarios with high βN (>3) and confinement enhancement over ITER98(y, 2) scaling, HH98y2 = 1.1–1.5, in steady state. These discharges been obtained a modified divertor configuration for Upgrade, allowing operation higher triangularity, changed neutral beam injection (NBI) system, more tangential, off-axis deposition. The figure of merit, βNHITER89-P, reaches up to 7.5 several seconds plasmas approaching stationary conditions....
Mechanisms underlying the retention of fuel species in tokamaks with carbon plasma-facing components are presented, together estimates for corresponding tritium ITER. The consequential requirement new and improved schemes to reduce inventory is highlighted results ongoing studies into a range techniques removal rate ITER each case. Finally, an approach involving integration many operational schedule proposed as means extend period operations before major intervention required.