A5072769495- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Nuclear Physics and Applications
- Structural Health Monitoring Techniques
- Magnetic Properties and Applications
- Magnetic Field Sensors Techniques
- Metal and Thin Film Mechanics
- Infrastructure Maintenance and Monitoring
- High-Energy Particle Collisions Research
- Semiconductor materials and devices
- Photocathodes and Microchannel Plates
- Non-Destructive Testing Techniques
- Fluid Dynamics and Turbulent Flows
- Geophysics and Gravity Measurements
- GNSS positioning and interference
- Vehicle emissions and performance
- Particle Detector Development and Performance
Princeton Plasma Physics Laboratory
2019-2025
TU Wien
2014-2025
North Carolina State University
2022-2024
University of Wisconsin–Madison
2022
General Atomics (United States)
2022
University of California, Los Angeles
2022
Fusion Academy
2016-2021
Fusion (United States)
2016-2021
Oak Ridge National Laboratory
2021
Plasma Technology (United States)
2021
Experimental evidence for the impact of a region high density localised in high-field side scrape-off layer (the HFSHD) on plasma confinement is shown various dedicated experiments ASDEX Upgrade (AUG). Increasing main ion fuelling to increase separatrix and shift profile outwards. Predictive pedestal modelling this indicates 25% decrease attainable top pressure, which compares well with experimental observations gas scan.
The lithium beam emission spectroscopy (Li-BES) is a powerful diagnostic to resolve the plasma edge density with high temporal and spatial resolution.The recent upgrades of Li-BES at ASDEX Upgrade resulting gain in photon flux allow be determined an advanced level accuracy.Furthermore, electron fluctuations are measured using Li-BES.The capabilities limitations measure profiles as well presented.Li-BES suited characterize turbulence scrape off layer (SOL) decreasing sensitivity towards...
In order to understand the mechanisms that determine structure of high confinement mode (H-mode) pedestal, evolution plasma edge electron density and temperature profiles between localised modes (ELMs) is investigated. The onset radial magnetic fluctuations with frequencies above 200 kHz found correlate stagnation pedestal gradient. During presence these gradients are clamped stable against ELM onset. detected fluctuation frequency analysed for a variety discharges different pressure...
The development of small Edge Localized Mode (ELM) scenarios is important in order to reduce the strain on plasma facing components.One such scenario can be found at high densities, highly shaped, close double-null plasmas ASDEX Upgrade, showing ELMs characterized by a frequency f ELM > 300Hz and low power loss.Changing from gas fuelling pellet results edge profiles which collisionality pedestal top separatrix are decoupled.While values remain unchanged, only phases with scrape-off layer...
Abstract The ‘Super H-Mode’ regime is predicted to enable pedestal height and fusion performance substantially higher than standard H-Mode operation. This exists due a bifurcation of the pressure, as function density, that by EPED model occur in strongly shaped plasmas above critical density. Experiments on Alcator C-Mod DIII-D have achieved access Super (and Near H) regime, obtained very high including highest tokamak ( p ped ~ 80 kPa) experiments operating near ITER magnetic field. H...
Multimachine empirical scaling predicts an extremely narrow heat exhaust layer in future high magnetic field tokamaks, producing power densities that require mitigation. In the experiments presented, width of this is nearly doubled using actuators to increase turbulent transport plasma edge. This achieved low collisionality, confinement edge pedestals with their gradients limited by instead large-scale, coherent instabilities. The flux profile and divertor leg diffusive spreading both double...
Abstract Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using manipulator II (DIM-II) system (Herrmann et al 2015 Fusion Eng. Des . 98–9 1496–9). Designed as near replicas geometries used also separate experiments on JET tokamak (Coenen J. Nucl. Mater 463 78–84; Coenen 55 023010; Matthews 2016 Phys. Scr T167 7), featured a...
The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport combined with ray tracing. data is compared to synthetic generated 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. amplitudes helical displacement around low side midplane are...
Abstract The plasma and neutral density dynamics after an edge localized mode are investigated utilized to infer the transport coefficients for pedestal. Lyman-Alpha Measurement Apparatus (LLAMA) diagnostic provides sub-millisecond profile measurements of ionization shows significant poloidal asymmetries in both. Exploiting absolute calibration LLAMA allows quantitative comparison electron main ion profiles determined by charge-exchange recombination, Thomson scattering interferometry....
Abstract Limit-cycle oscillations (LCOs) close to the power threshold of L- H-mode transitions are investigated in plasmas ASDEX Upgrade. During this phase, referred as I-phase, a strong magnetic activity poloidal field <?CDATA ${{\overset{\centerdot}{{B}}\,}_{\theta}}$ ?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mi>B</mml:mi> <mml:mo>⋅</mml:mo> </mml:mover> </mml:mstyle>...
Abstract The spatio-temporal interplay between turbulence, mean and zonal flows has been investigated at the L–H H–L transitions in edge region of ASDEX Upgrade tokamak. Close to both transitions, an intermediate phase (I-phase) characterized by ‘limit cycle like oscillations’ (LCOs) is observed which periodic bursts turbulence correlate with <?CDATA $\mathbf{E}\times \mathbf{B}$ ?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false">...
Results of experimental scans heating power, plasma shape, and nitrogen content are presented, with a focus on global performance pedestal alteration.In detailed at low triangularity, it is shown that the increase in stored energy due to seeding stems mainly from pedestal, small additional contribution increased core density peaking.It also confinement driven through temperature three power levels studied.In triangularity scan, an orthogonal effect shaping observed, where increases density,...
The injection of boron (B) and nitride (BN) powders into ASDEX Upgrade H-mode discharges have demonstrated effective control tungsten influx in low density/collisionality operational regimes, similar to conventional boronization methods. Sub-mm powder particles are gravitationally accelerated the upper edge a lower single null plasma with boundary shape roughly conforming poloidal midplane limiters. Visible spectroscopy measurements at one outer limiter showed increases both B N signal...
The efficacy of boron powder injection as a wall conditioning tool method in terms its ability to create sufficiently uniform layer on plasma-facing surfaces has been studied ASDEX Upgrade. Boron was injected two series dedicated plasma discharges at varied rates and total amount injected. resulting deposition determined quantitatively by exposure witness samples followed ex-situ surface analysis the retrieved samples. In both experiments, isotopically enriched used distinguish newly...
Abstract Experimental measurements on DIII-D of hydrogen neutral penetration lengths ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mi>n</mml:mi> <mml:mn>0</mml:mn> </mml:msub> </mml:mrow> </mml:math> ) the high field side (HFS) are longer by a factor <mml:msqrt> <mml:mn>2</mml:mn> </mml:msqrt> than for deuterium consistent with thermal velocity ratio neutrals at same temperature <mml:mo stretchy="false">(</mml:mo>...
The magnetic field dependence of intermittently expelled density filaments (blobs) is investigated in the scrape-off layer ASDEX Upgrade low confinement (L-mode) plasmas.It demonstrated that lithium beam emission spectroscopy can be used to determine frequency, radial size and velocity blobs.The measured blob sizes depend only weakly on B. Normalizing drift parameter ρs ∝ B -1 results a large variation beneficial for quantitative comparison with theoretical scaling laws.The scales inversely...
The dynamics of blob filaments are investigated in the scrape-off layer ASDEX Upgrade by means lithium beam emission spectroscopy. A comparison measurements L-mode with a recently developed analytical model based on drift-interchange-Alfvén fluid indicates an influence finite ion temperature which has typically been neglected other models. agree well sheath-connected regime at lower plasma densities, and inertial effects play only minor role. At higher transition into another large...
In highly confined tokamak plasmas periodically appearing edge localized modes (ELMs) are accompanied by mode-like magnetohydrodynamic (MHD) activities with defined toroidal mode numbers.
A variety of experimental studies on pedestal localized fluctuations appearing in between crashes edge modes (ELMs) across several tokamaks have been reviewed and summarized. The onset the inter-ELM is correlated with evolution gradients. Three profile recovery phases are extracted, which interlinked onsets different kinds fluctuations. Across machines it found that can be assorted into at least three categories. These determined by fluctuation ELM cycle, observed frequency range radial...
A one dimensional, absolutely calibrated pinhole camera system was installed on the DIII-D tokamak to measure edge Lyman-alpha (Ly-α) emission from hydrogen isotopes, which can be used infer neutral density and ionization rate profiles. The is composed of two cameras, each providing a toroidal fan 20 lines sight, viewing plasma inboard outboard side DIII-D. cameras’ views lie in horizontal plane 77 cm below midplane. At its tangency radius, channel provides radial resolution ∼2 full width at...
Abstract The edge localized mode (ELM) frequency ( f ELM ) decreased by 63% when electron cyclotron heating (ECH) deposition location is shifted from ρ = 0.4 to 0.8 in DIII-D discharges where the power ratio between neutral beam injection (NBI) and ECH P NBI / kept at ∼1. performance of pedestal heated case compared with a pure reference discharge while keeping total input constant. All these are performed balanced torque conditions. Furthermore, strong decoupling peeling–ballooning (PB)...
The upgrade of the edge charge exchange recombination spectroscopy diagnostic at ASDEX Upgrade (AUG) has enabled highly spatially resolved measurements impurity ion dynamics during an edge-localized mode cycle (ELM) with unprecedented temporal resolution, i.e. 65 µs.The increase transport ELM induces a relaxation ion, electron gradients in density and flows.Detailed characterization recovery temperature reveals difference channel: maximum gradient ∇T i is reestablished on similar timescales...
The L-H transition power threshold (P ) in full tungsten (W) wall discharges is lower by 25% compared to those with graphite (C) mix walls ASDEX Upgrade [Ryter F, et al. 2013 Nucl.Fusion].The the has been found correlate higher edge density as well steeper gradient.An estimate of minimum neoclassical radial electric field inside separatrix yields a constant value for all analyzed transitions at fixed toroidal magnetic (B T ).The decrease explained gradient wall.
Abstract The ion heat transport in the pedestal of H-mode plasmas is investigated various discharges with different collisionalities. Interpretive modelling suggests that all analyzed diffusivity coefficient, <?CDATA ${{\chi}_{\text{i}}}$ ?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mstyle displaystyle="false"> <mml:msub> <mml:mrow> <mml:mi>χ</mml:mi> </mml:mrow> <mml:mi mathvariant="normal">i</mml:mi> </mml:msub> </mml:mstyle> </mml:math> , close to...
In a series of discharges on the DIII-D tokamak, fast vertical plasma jogs are used to induce current perturbations in steep gradient region H-mode edge. These directly influence edge q profile, decoupling resonant location and instability drive pedestal-localized microtearing modes (MTMs.) By exploiting this effect, we develop apply new experimental technique track dynamical frequency evolution MTMs pedestal region, providing compelling validation MTM model. The potential is calculated as...