A5045125803- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Nuclear Engineering Thermal-Hydraulics
- Advanced Data Storage Technologies
- Atomic and Subatomic Physics Research
- Astronomical Observations and Instrumentation
- Spacecraft and Cryogenic Technologies
- Adhesion, Friction, and Surface Interactions
- Inhalation and Respiratory Drug Delivery
- Nuclear Materials and Properties
- Heat Transfer and Optimization
- Vehicle emissions and performance
- Electronic Packaging and Soldering Technologies
- Astro and Planetary Science
- Heat Transfer and Boiling Studies
- Rare-earth and actinide compounds
- Metallurgical Processes and Thermodynamics
- Laser-induced spectroscopy and plasma
- Semiconductor materials and devices
University of Tennessee at Knoxville
2021-2025
General Atomics (United States)
2019-2021
Oak Ridge Associated Universities
2018-2019
Max Planck Institute for Plasma Physics
2013-2018
Max Planck Society
2013-2015
A future fusion reactor is expected to have all-metal plasma facing materials (PFMs) ensure low erosion rates, tritium retention and stability against high neutron fluences. As a consequence, intrinsic radiation losses in the edge divertor are comparison devices with carbon PFMs. To avoid localized overheating divertor, low-Z medium-Z impurities be inserted into convert major part of power flux facilitate partial detachment. For burning conditions ITER, which operates not far above L–H...
Detachment of high power discharges is obtained in ASDEX Upgrade by simultaneous feedback control core radiation and divertor or thermoelectric currents the injection radiating impurities. So far 2/3 ITER normalized heat flux Psep/R = 15 MW m−1 has been under partially detached conditions with a peak target well below 10 m−2. When detachment further pronounced towards lower at target, substantial changes edge localized mode (ELM) behaviour, density distribution occur. The time-averaged both...
Abstract Negative triangularity (NT) is a potentially transformative configuration for tokamak-based fusion energy with its high-performance core, edge localized mode (ELM)-free edge, and low-field-side divertors that could readily scale to an integrated reactor solution. Previous NT work on the TCV DIII-D tokamaks motivated installation of graphite-tile armor lower outer wall DIII-D. A dedicated multiple-week experimental campaign was conducted qualify scenario future reactors. During...
A new small angle slot (SAS) divertor concept has been developed to enhance neutral cooling across the target by coupling a closed structure with appropriate shaping. Initial tests on DIII-D find strong interplay between such anticipated 'SAS' effects and cross-field drifts, favouring operation ion B × ∇B drift away from X-point, as currently employed for advanced tokamaks. This offers following key improvements relative DIII-D's open lower or partially-closed upper divertor: (i) SAS allows...
Impurity seeding studies in the small angle slot (SAS) divertor at DIII-D have revealed a strong relationship between detachment onset and pedestal characteristics with both target geometry impurity species. N2 has led to first simultaneous observation of on entire suite boundary diagnostics viewing SAS without degradation core confinement. SOLPS-ITER simulations D+C+N, full cross field drifts, n–n collisions activated are performed for time interpret behavior. This highlights effect...
Edge-localized mode (ELM) triggering and pacing in an all-metal wall environment shows significant differences to a first-wall configuration containing carbon. Here we report on experiments performed at ASDEX Upgrade revisiting the issue with all plasma-facing surfaces now fully replaced by tungsten. This investigation was motivated experimental findings indicating that ELM becomes more intricate when carbon is metal wall. could no longer be achieved magnetic under conditions previously...
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat particle loads on wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research ASDEX Upgrade (AUG), MAST TCV. This multi-machine approach within EU-MST, covering wide parameter range, instrumental progress in field, as ITER DEMO core/pedestal SOL parameters are not achievable simultaneously present day devices. A two prong adopted. On one...
Comparison between an open divertor and a more-closed in DIII-D demonstrates detachment up to 40% lower pedestal density (ne,ped) the closed due combination of decreased fueling increased dissipation scrape off layer (SOL) divertor, both resulting from neutral trapping divertor. Predicting whether relationship closure will hold for opaque SOL, which contribution ionizing neutrals is lessened, requires separating out different mechanisms contributing difference at detachment. A series...
The effect of divertor closure on neutral leakage, power dissipation and pedestal fueling is investigated using the SOLPS code for different densities including attached detached conditions DIII-D open closed divertors. In this work, a metric in terms percentage neutrals escaping presented. At detachment onset population 12% 35% divertor. This results lower contribution convective term to total heat flux increased losses comparison between two geometries reveals that same upstream density,...
Abstract We present a new framework for core-edge integration studies named SICAS (SOLPS-ITER coupled to ASTRA-STRAHL) which enables simulations of the core, edge, and divertor regions describing self-consistently transport ions as well impurities through entire plasma domain. handles exchanging particle power fluxes coefficients ensure consistency codes. An overlapping region is defined from inside separatrix SOLPS-ITER core boundary allowing matching profiles between two codes...
Local neutral pressure measurements in the closed small angle slot (SAS) divertor [1,2] on DIII-D show a large increase when plasma shifts from high recycling into detachment. In-tile gauges were installed to measure near- and far-SOL regions examine predicted pressures compression. Cross-field drift effects lead ∼ 10 × higher peak detachment with ion ∇B toward compared out of divertor, similar attached conditions. Drifts also play role distribution while but become less pronounced once...
Abstract A comparative study of nitrogen versus neon has been carried out to analyze the impact two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in divertor, thereby providing high losses without affecting profiles displacing carbon as dominant radiator. Neon, instead, radiates more upstream than thus reducing flux through separatrix leading a reduced ELM frequency compression...
The small-angle slot (SAS) divertor of the DIII-D tokamak, and its upcoming upgrade, V-shape (SAS-V) divertor, are numerically investigated using SOLPS-ITER code package, including effect particle drifts, for a range plasma density, heating power, strike point position in slot, both magnetic field directions. simulations show that electron temperature near is reduced SAS-V compared to SAS, directions, such achieves detachment at lower value outboard mid-plane separatrix density. threshold...
Abstract DIII-D physics research addresses critical challenges for the operation of ITER and next generation fusion energy devices. This is done through a focus on innovations to provide solutions high performance long pulse operation, coupled with fundamental plasma understanding model validation, drive scenario development by integrating core boundary plasmas. Substantial increases in off-axis current efficiency from an innovative top launch system EC power, pressure broadening Alfven...
SOLPS5.1 modelling of first detachment experiments carried out in the new Small Angle Slot (SAS) divertor recently installed at DIII-D has indicated a significant reduction Te strike point compared to matched open case for given separatrix density. The SAS combines gas-tight slot geometry with small target angle bootstrap power and momentum dissipation recycling neutrals goal achieving simultaneous control heat flux erosion relatively low plasma density required non-inductive current drive...
SOLPS modelling has shown that divertor plasma detachment occurs at a lower upstream separatrix density in the more closed DIII‐D upper than open divertor, demonstrating utility of closure widening range acceptable densities for adequate heat handling. To achieve reduced flux and erosion plasma‐facing components, future devices will need to operate least partially detached conditions . Two‐dimensional fluid models coupled Monte Carlo neutral transport simulations, such as SOLPS, have been...
Experiments using nitrogen were conducted in H-mode plasmas at ASDEX Upgrade that has a full-W wall. The edge region of is modulated by the edge-localized modes (ELMs) which lead to loss energy and particles from confined plasma. In order gain better understanding complex physical mechanisms govern behaviour radiation impurities presence ELMs, evolution been modelled time-dependent way. simulations have carried out with ASTRA-STRAHL package featuring self-consistent interplay between...
Experiments with low-Z powder injection in DIII-D high confinement discharges demonstrated increased divertor dissipation and detachment while maintaining good core energy confinement. Lithium (Li), boron (B), nitride (BN) powders were injected high-confinement mode plasmas ($I_p=$1 MA, $B_t=$2 T, $P_{NB}=$6 MW, $\langle n_e\rangle=3.6-5.0\cdot10^{19}$ m$^{-3}$) into the upper small-angle slot (SAS) for 2-s intervals at constant rates of 3-204 mg/s. The multi-species BN a rate 54 mg/s showed...
The ASDEX Upgrade tokamak is equipped with a 5-channel DCN interferometer probing wavelength of 195 μm. Up to now, phase measurement and density calculation have been accomplished by hard-wired counting electronics. Meanwhile, fast digitizer has installed which acquires the raw signals. That way, various causes errors integer multiples 2π, so-called fringe jumps, can be analyzed, reconstruction schemes based on digital signal processing developed. In addition, prototype polarimeter setup one...
Abstract The DIII-D tokamak has elucidated crucial physics and developed projectable solutions for ITER fusion power plants in the key areas of core performance, boundary heat particle transport, integrated scenario operation, with closing core-edge integration knowledge gap being overarching mission. New experimental validation high-fidelity, multi-channel, non-linear gyrokinetic turbulent transport models provides strong confidence it will achieve Q ⩾ 10 operation. Experiments identify...
Abstract Experiments with extrinsic impurity seeding in strongly negative triangularity shapes DIII-D achieved radiated power fractions (relative to input power) of up ≈85% total radiation and ≈55% core steady-operating conditions. The relationship between was sensitive species power. Attempts reach higher levels via flows resulted radiative collapse disruptions. Nitrogen, neon, argon, krypton were tested. Injection by gas puffing, usually controlled feeding back real-time estimates for or...
Abstract The first achievement of highly radiating plasmas in negative triangularity is shown with an operational space featuring high core radiation at Greenwald fraction obtained the injection reactor-relevant seeded gases. These (NT) shape diverted discharges reach values normalized plasma pressure (BN > 2) no ELMs and a simultaneous reduction divertor heat flux. We demonstrate that as long impurity level kept low to avoid excessive fuel dilution accumulation, integration NT...
Future fusion reactors, foreseen in the "European road map" such as DEMO, will operate under more demanding conditions compared to present devices. They require high divertor and core radiation by impurity seeding reduce heat loads on target plates. In addition, DEMO have work at densities reach adequate performance. The performance of reactors depends three essential parameters: temperature, density energy confinement time. latter characterizes loss rate due both transport processes....
The path to fusion in the United States requires partnership between public and private sector. While sector provides vigor take some of major steps necessary, there is a depth expertise capability that vital resolving feasible approaches. As an open national user facility, DIII-D crucial testbed develop required new technologies approaches relevant conditions. It has unparalleled potential meet this challenge, thanks its extreme flexibility world leading diagnostics. This basis rapidly...