A5001094425- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Semiconductor materials and devices
- Solar and Space Plasma Dynamics
- Electrostatic Discharge in Electronics
- Laser-induced spectroscopy and plasma
- Physics of Superconductivity and Magnetism
- Advancements in Semiconductor Devices and Circuit Design
- Dust and Plasma Wave Phenomena
- Semiconductor Quantum Structures and Devices
- Nuclear reactor physics and engineering
- Advanced Data Storage Technologies
- Thin-Film Transistor Technologies
- Silicon and Solar Cell Technologies
- Atomic and Subatomic Physics Research
- Atomic and Molecular Physics
- Silicon Carbide Semiconductor Technologies
- Fluid Dynamics and Turbulent Flows
- High-Energy Particle Collisions Research
- Phase-change materials and chalcogenides
General Atomics (United States)
2016-2025
University of Wisconsin–Madison
1979-2021
University of California, Los Angeles
2010-2021
The University of Texas at Austin
2020-2021
University of California, San Diego
2009-2021
University of York
2009-2013
Culham Centre for Fusion Energy
2013
Culham Science Centre
2011-2013
Oak Ridge National Laboratory
2005-2009
Fusion Academy
2002
The pressure at the top of edge transport barrier (or “pedestal height”) strongly impacts tokamak fusion performance. Predicting pedestal height in future devices such as ITER [ITER Physics Basis Editors, Nucl. Fusion 39, 2137 (1999)] remains an important challenge. While uncertainties remain, magnetohydrodynamic stability calculations intermediate wavelength (the “peeling-ballooning” model), accounting for diamagnetic stabilization, have been largely successful determining observed maximum...
Abstract The tokamak approach, utilizing a toroidal magnetic field configuration to confine hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion generate electrical energy 1,2 . To reach goal an economical reactor, reactor 3–10 simultaneously require reaching plasma line-averaged density above empirical limit—the so-called Greenwald 11 —and attaining confinement quality better than standard high-confinement mode 12,13 However, such...
The pressure at the top of edge transport barrier (or ‘pedestal height’) strongly impacts fusion performance, while large localized modes (ELMs), driven by free energy in pedestal region, can constrain material lifetimes. Accurately predicting height and ELM behavior ITER is an essential element prediction optimization performance. Investigation intermediate wavelength MHD ‘peeling–ballooning’ modes) has led to improved understanding important constraints on mechanism for ELMs. combination...
Following boronization, tokamak discharges in DIII-D have been obtained with confinement times up to a factor of 3.5 above the ITER89-P L-mode scaling and 1.8 greater than DIII-D/JET H-mode relation. Very high phases are characterized by relatively central density ${\mathit{n}}_{\mathit{e}}$(0)\ensuremath{\approxeq}1\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$, ion temperatures 13.6 keV at moderate plasma currents (1.6 MA) heating powers (12.5--15.3...
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 EPED model predicts the H-mode pedestal height and width based upon two fundamental calculable constraints: (1) onset of non-local peeling-ballooning modes at low to intermediate mode number, (2) nearly local kinetic ballooning high number. We present detailed tests in discharges with edge localized (ELMs), employing new resolution measurements, finding good quantitative agreement across a range parameters. is then applied for first time quiescent (QH), similar level between predicted...
Rapid bifurcations in the plasma response to slowly varying $n=2$ magnetic fields are observed as transitions into and out of edge-localized mode (ELM) suppression. The rapid transition ELM suppression is characterized by an increase toroidal rotation a reduction electron pressure gradient at top pedestal that reduces perpendicular flow there near zero. These events occur simultaneously with inner-wall response. observations consistent strong resonant field penetration onset suppression,...
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...
Abstract Lithium wall coatings have been shown to reduce recycling, suppress edge-localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document effect of gradually increasing lithium on discharge characteristics, with reference ELMy discharges obtained boronized, i.e. non-lithiated conditions. We observed a continuous but not quite monotonic reduction recycling improvement confinement, gradual alteration edge plasma profiles,...
High repetition rate injection of deuterium pellets from the low-field side (LFS) DIII-D tokamak is shown to trigger high-frequency edge-localized modes (ELMs) at up $12\ifmmode\times\else\texttimes\fi{}$ low natural ELM frequency in $H$-mode plasmas designed match ITER baseline configuration shape, normalized beta, and input power just above threshold. The pellet size, velocity, location were chosen limit penetration outer 10% plasma. resulting perturbations plasma density energy...
Comprehensive 2D turbulence and eddy flow velocity measurements on DIII-D demonstrate a rapidly increasing turbulence-driven shear that develops $\ensuremath{\sim}100\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ prior to the low-confinement ($L$ mode) high-confinement ($H$ transition appears trigger it. These changes are localized narrow layer 1--2 cm inside magnetic boundary. Increasing heating power increases Reynolds stress, energy transfer from poloidal flow, edge shearing rate then...
In a series of high performance diverted discharges on DIII-D, we demonstrate that strong negative triangularity (NT) shaping robustly suppresses all edge-localized mode (ELM) activity over wide range plasma conditions: ⟨n⟩=0.1-1.5×10^{20} m^{-3}, P_{aux}=0-15 MW, and |B_{t}|=1-2.2 T, corresponding to P_{loss}/P_{LH08}∼8. The full dataset is consistent with the theoretical prediction magnetic shear in NT edge inhibits access ELMing H-mode regimes; experimental pressure profiles are found be...
Abstract Strongly-shaped diverted negative triangularity (NT) plasmas in the DIII-D tokamak demonstrate simultaneous access to high normalized density, current, pressure, and confinement. NT are shown exist across an expansive parameter space compatible with fusion power production, revealing surprisingly good core stability properties that compare favorably conventional positive DIII-D. Non-dimensionalizing key parameters, expanded operating spaces featuring edge safety factors below 3,...
Using newly developed techniques and improved diagnostics, rotating wall-stabilized discharges have been maintained in the DIII-D tokamak for 30 characteristic resistive wall decay times---significantly longer than was previously achieved. The terminating mode has directly identified using internal fluctuation its correlation with slowdown plasma rotation is established.
The instrument function of the high resolution Thomson scattering (HRTS) diagnostic in Joint European Torus (JET) has been calculated for use improved pedestal profile analysis. full width at half maximum (FWHM) spatial response is (22 ± 1) mm original HRTS system configuration and depends on particular magnetic topology JET plasmas. An improvement to optical design laser input presented. smearing across flux surfaces reduced this design. new implemented (from JPN 78742, July 2009)...
A comprehensive set of L–H transition experiments has been performed on DIII-D to determine the requirements for access H-mode plasmas in ITER's first (non-nuclear) operational phase with H and He second (activated) D plasmas. The power threshold, P TH , was evaluated different configurations auxiliary heating methods main ion species. Helium have significantly higher than deuterium at low densities all schemes, but similar as high except H-neutral beam injection-heated discharges, which are...
In both JET and ASDEX Upgrade (AUG) the plasma energy confinement has been affected by presence of a metal wall requirement increased gas-fuelling to avoid tungsten pollution plasma.In with beryllium/tungsten high triangularity baseline H-mode scenario (i.e.similar ITER reference scenario) strongest benefit shaping give good normalised H 98 ~1 at Greenwald density fraction f GW ~0.8 disappeared.In AUG full could be achieved in plasmas, albeit elevated pressure β N >2.The lost respect carbon...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation M. N. A. Beurskens, T. H. Osborne, P. Schneider, E. Wolfrum, L. Frassinetti, R. Groebner, Lomas, I. Nunes, S. Saarelma, Scannell, B. Snyder, D. Zarzoso, Balboa, Bray, Brix, J. Flanagan, C. Giroud, Giovannozzi, Kempenaars, Loarte, de la Luna, G. Maddison, F. Maggi, McDonald, Pasqualotto, Saibene, Sartori, Emilia...
Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on amount of predischarge lithium evaporation. We observed a nearly monotonic reduction decrease electron transport, modification profiles stability with increasing lithium. These correlations challenge basic expectations, given even smallest exceeded needed for nominal...
Direct measurements of the pedestal recovery during an edge-localized mode cycle provide evidence that quasi-coherent fluctuations (QCFs) play a role in inter-ELM dynamics. Using fast Thomson scattering measurements, density and temperature evolutions are probed on sub-millisecond time scales to show gradient compared gradient. The appears drive for onset (as measured with magnetic probe diagnostics) localized pedestal. amplitude evolution these QCFs tracks including its saturation. Such...
Abstract This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport no localized modes (ELMs). The regime has been demonstrated on Alcator C-Mod, ASDEX Upgrade DIII-D tokamaks, over a wide range device parameters pedestal conditions. Dimensionless at show overlap across devices extend to low collisionality. When they are matched, temperature profiles also similar. Pedestals stable...
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...
Abstract Experiments performed during strongly-shaped high-power diverted negative triangularity (NT) experiments in DIII-D achieved detached divertor conditions and a transient-free edge, showcasing the potential for application of NT to core-edge integrated reactor-like scenario providing first characterization parametric dependencies detachment onset. Detached will be required future devices mitigate heat fluxes. Access dissipative was investigated via an increase upstream density....
The frequency of type-I ELMs decreases as the initiation neutral beam injection (NBI) heating is delayed with respect to time when plasma current (Ip) reaches flat-top in ITER Baseline Scenario discharges DIII-D. Henceforth, gap between NBI and Ip will be referred “heating delay.” As delay modified, pedestal formation follows different trajectories edge density–pedestal pressure gradient (jedge−∇peped) space from L-H transition toward first ELM event. During stationary phase after ELM,...