A5081781859- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Semiconductor materials and devices
- Laser-induced spectroscopy and plasma
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Gyrotron and Vacuum Electronics Research
- Silicon and Solar Cell Technologies
- Advanced Data Storage Technologies
- Advancements in Semiconductor Devices and Circuit Design
- Thin-Film Transistor Technologies
- Physics of Superconductivity and Magnetism
- Particle Accelerators and Free-Electron Lasers
- Nuclear Materials and Properties
- Atomic and Molecular Physics
- Catalytic Processes in Materials Science
- Semiconductor Quantum Structures and Devices
- Gas Dynamics and Kinetic Theory
- GaN-based semiconductor devices and materials
Lawrence Livermore National Laboratory
2015-2024
General Atomics (United States)
1998-2018
University of California, San Diego
2005-2017
William & Mary
2017
Williams (United States)
2017
University of California, Los Angeles
2005-2017
Princeton Plasma Physics Laboratory
2015-2017
Columbia University
2015-2017
Oak Ridge Associated Universities
2017
Oak Ridge Institute for Science and Education
2017
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...
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...
Understanding the physics of edge pedestal and localized modes (ELMs) is great importance for ITER optimization tokamak concept. The peeling–ballooning model has quantitatively explained many observations, including ELM onset constraints, in standard H-mode regime. ELITE code been developed to efficiently evaluate stability comparison with observation predictions future devices. We briefly review recent progress model, experimental validation height predictions, nonlinear 3D simulations...
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...
Dust production and accumulation present potential safety operational issues for the ITER. diagnostics can be divided into two groups: of dust on surfaces in plasma. Diagnostics from both groups are employed contemporary tokamaks; new suitable ITER also being developed tested. is likely to occur hidden areas, e.g., between tiles under divertor baffles. A novel electrostatic detector monitoring these regions has been tested at PPPL. In DIII-D tokamak include Mie scattering Nd:YAG lasers,...
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,...
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...
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...
Recent DIII-D [J. L. Luxon et al., Nucl. Fusion 43, 1813 (2003)] experiments show a correlation between the extent of overlap magnetic islands induced in edge plasma by perturbation coils and complete suppression Type-I localized modes (ELMs) plasmas with ITER-like electron pedestal collisionality νe*∼0.1, flux surface shape low safety factor (q95≈3.6). With fixed amplitude n=3 resonant (RMP), ELM is obtained only finite window (q95) consistent maximizing component applied helical field....
Periods of edge localized mode (ELM)-free H-mode with increased pedestal pressure and width were observed in the DIII-D tokamak when density fluctuations to region near separatrix present. Injection a powder 45 µm diameter lithium particles duration enhanced phases up 350 ms, also likelihood transition phase. Lithium injection at level sufficient for triggering extended resulted significant plasma core, but carbon other higher Z impurities as well radiated power levels reduced. Recycling...
Operating ITER in the reference inductive scenario at design values of Ip = 15 MA and QDT 10 requires achievement good H-mode confinement that relies on presence an edge transport barrier whose pedestal pressure height is key to plasma performance. Strong gradients occur such conditions can drive magnetohydrodynamic instabilities resulting localized modes (ELMs), which produce a rapid energy loss from region facing components (PFC). Without appropriate control, heat loads PFCs during ELMs...
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...
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...
Small non-axisymmetric perturbations of poloidally diverted tokamaks create edge stochastic magnetic field lines that connect to material surfaces such as those in the divertors. Separatrix structure calculations show distribution on vessel walls is closely related topology homoclinic tangles formed perturbed system. Since these prescribe how fields are organized, they significant practical interest tokamak experiments. Experimental measurements heat and particle distributions plasma facing...
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 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...
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...
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....
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...
The energy lost from the pedestal region due to an average ELM in DIII-D is determined changes electron density and temperature profiles as measured by Thomson scattering. loss of associated with conduction found decrease increasing density. density, or convective transport, remains constant a function scaling two transport channels, convection, are examined terms parallel processes scrape-off-layer divertor.