A5034517222- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Nuclear Materials and Properties
- Semiconductor materials and devices
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Advanced Data Storage Technologies
- Electrostatic Discharge in Electronics
- Silicon Carbide Semiconductor Technologies
- Silicon and Solar Cell Technologies
- Advancements in Semiconductor Devices and Circuit Design
- Metallurgical Processes and Thermodynamics
- Diamond and Carbon-based Materials Research
- Advanced Materials Characterization Techniques
- Ion-surface interactions and analysis
- Fluid Dynamics and Turbulent Flows
- Electron and X-Ray Spectroscopy Techniques
Sandia National Laboratories
2015-2024
Sandia National Laboratories California
2015-2024
General Atomics (United States)
2000-2024
University of California Davis Medical Center
2024
University of California, San Diego
2005-2022
Lawrence Livermore National Laboratory
1997-2022
Oak Ridge National Laboratory
2016-2018
Oak Ridge Associated Universities
2017-2018
Knoxville College
2018
University of Tennessee at Knoxville
2018
A stochastic magnetic boundary, produced by an applied edge resonant perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement ($H$-mode) plasmas. The resulting $H$ mode displays rapid, small oscillations with a bursty character modulated coherent 130 Hz envelope. transport barrier and core are unaffected the despite threefold drop toroidal rotation. These results demonstrate that boundaries compatible may be attractive for ELM control next-step fusion tokamaks.
Large Type-I edge localized modes (ELMs) are completely eliminated with small n = 3 resonant magnetic perturbations (RMP) in low average triangularity, , plasmas and ITER similar shaped (ISS) plasmas, relevant collisionalities . Significant differences the RMP requirements properties of ELM suppressed found when comparing two triangularities. In ISS current required to suppress ELMs is approximately 25% higher than triangularity plasmas. It also that width q95 window for suppression smaller...
Metallic mirrors will be used in ITER for optical diagnostics working different spectral ranges. Their properties change with time due to erosion, deposition, and particle implantation. First tests of molybdenum were performed the DIII-D divertor under deposition-dominated conditions. Two sets recessed 2cm below floor private flux region exposed a series identical, lower-single-null, ELMing (featuring edge localized modes) H-mode discharges detached plasma conditions both legs. The first set...
Toroidicity induced Alfven eigenmodes (TAE) are observed in the DIII-D tokamak when energetic beam ions ( approximately 75 keV) used to destabilize mode. Measurements of neutron emission indicate that up 70% injected power is lost during strong TAE activity. poloidal distribution fast ion losses suggest greatest near vessel midplane. Fast discharges with combined fishbones and bursts 1.5 2 times greater than fishbone without TAB The scaling MHD mode amplitude exhibits no threshold amplitude,...
High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge localized modes (ELMs). ELMs can produce erosion in divertor affect beta limit reduced core transport regions needed operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency,...
Large sub-millisecond heat pulses due to Type-I edge localized modes (ELMs) have been eliminated reproducibly in DIII-D for periods approaching nine energy confinement times (τE) with small dc currents driven a simple magnetic perturbation coil. The current required eliminate all but few isolated ELM impulses during coil pulse is less than 0.4% of plasma current. Based on field line modelling, the fields resonate flux surfaces across most pedestal region (0.9 ⩽ ψN 1.0) when q95 = 3.7 ± 0.2,...
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...
In this paper the manipulation of power deposition on divertor targets at DIII-D by application resonant magnetic perturbations (RMPs) for suppression large type-I edge localized modes (ELMs) is analysed. We discuss modification ELM characteristics RMP applied. It shown that width pattern in ELMy H-mode depends linearly deposited energy, whereas phase discharge those patterns are controlled externally induced perturbation. was also found heat transport due to small, plasma pedestal electron...
A coordinated effort to measure divertor heat flux characteristics in fully attached, similarly shaped H-mode plasmas on C-Mod, DIII-D, and NSTX was carried out 2010 order construct a predictive scaling relation applicable next step devices including ITER, FNSF, DEMO. Few published laws are available those that have been were obtained under widely varying conditions geometries, leading conflicting predictions for this critically important quantity. This study designed overcome these...
Abstract Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation fusion reactors. Here, we demonstrate excellent compatibility actively controlled full divertor with high-performance ( β N ~ 3, H 98 1.5) core plasma, using high-β p (poloidal beta, > 2) scenario characterized by sustained internal transport barrier (ITB) and modest edge (ETB) in DIII-D tokamak. The high- high-confinement facilitates which, turn, promotes...
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...
H-mode operation is the choice for next-step tokamak devices based either on conventional or advanced physics. This choice, however, comes at a significant cost both and tokamaks because of effects edge-localized modes (ELMs). ELMs can produce erosion in divertor affect β limit reduced core transport regions needed operation. Recent experimental results from DIII-D have demonstrated new operating regime, quiescent which solves these problems. We achieved ELM-free yet has good density...
Cross-field fluctuation-driven transport is studied in edge and scrape-off layer (SOL) plasmas the DIII-D tokamak using a fast reciprocating Langmuir probe array allowing local measurements of particle heat fluxes. Two different non-diffusive mechanisms that can contribute strongly to cross-field SOL high-density discharges are identified compared. The first these involves intermittent events observed at plasma separatrix SOL. Intermittence has qualitatively similar character L-mode ELM-free...
Far Scrape-Off Layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge confinement regime. In L-mode discharges cross-field transport increases with average density flattens far SOL profiles, thus increasing contact low field side (LFS) main chamber wall. H-mode between edge localized modes (ELMs) plasma–wall is weaker than L-mode. During ELM fluxes of particles heat to LFS wall increase transiently above values. Depending conditions, ELMs are responsible for...
A study of three-dimensional (3D) perturbed magnetic field structures and transport for edge localized mode control experiments with resonant perturbations at DIII-D is presented. We focus on ITER-Similar Shape plasmas ITER relevant electron pedestal collisionalities . This performed in comparison results from TEXTOR-Dynamic Ergodic Divertor circular limiter plasmas. For both the structure analyzed vacuum paradigm—superimposing external RMP unperturbed equilibrium. TEXTOR L-mode this...
A low amplitude (δbr∕BT=1 part in 5000) edge resonant magnetic field perturbation with toroidal mode number n=3 and poloidal numbers between 8 15 has been used to suppress most large type I localized modes (ELMs) without degrading core plasma confinement. ELMs have suppressed for periods of up 8.6 energy confinement times when the safety factor q95 is 3.5 4. The are replaced by packets events (possibly II ELMs) small amplitude, narrow radial extent, a higher level density fluctuations,...
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...
The characteristics of the H-mode are studied in discharges with varying triangularity and squareness. pressure at top pedestal increases strongly triangularity, primarily due to an increase margin by which edge gradient exceeds ideal ballooning mode first stability limit. Two models considered for how may exceed In one model, access second stable regime allows associated bootstrap current continue until localized, low toroidal number, kink is destabilized. finite width transport barrier...
Using resonant magnetic perturbations with toroidal mode number n = 3, we have produced H-mode discharges without edge localized modes (ELMs) which run constant density and radiated power for periods up to about 2550 ms (17 energy confinement times). These ELM suppression results are achieved at pedestal collisionalities close those desired next step burning plasma experiments such as ITER provide a means of eliminating the rapid erosion divertor components in machines could be caused by...
Small edge resonant magnetic perturbations are used to control the pedestal transport and stability in low electron collisionality (νe*), ITER [ITER Physics Basis Editors et al., Nucl. Fusion 39, 2137 (1999)] relevant, poloidally diverted plasmas. The applied reduce height of density increase its width while increasing temperature gradient. effect on gradients is controlled by current perturbation coil, poloidal mode spectrum neutral beam heating power, divertor deuterium fueling rate. Large...
Joint experiment/theory/modelling research has led to increased confidence in predictions of the pedestal height ITER. This work was performed as part a US Department Energy Research Target FY11 identify physics processes that control H-mode structure. The study included experiments on C-Mod, DIII-D and NSTX well interpretation experimental data with theory-based modelling codes. provides ability models for peeling–ballooning stability, bootstrap current, width scaling make correct...
It is important to develop a predictive capability for the tungsten source rate near strike points during H-mode operation in ITER and beyond. deuterium plasma exposures were performed on W-coated graphite molybdenum substrates DIII-D divertor using DiMES. The W-I 400.9 nm spectral line was monitored by fast filtered diagnostics cross calibrated via high-resolution spectrometer resolve inter-ELM W erosion. effective ionization/photon (S/XB) unique method developed based surface analysis....
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...