A5024582470- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Semiconductor materials and devices
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Physics of Superconductivity and Magnetism
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Data Storage Technologies
- Dust and Plasma Wave Phenomena
- Silicon and Solar Cell Technologies
- Silicon Carbide Semiconductor Technologies
- Atomic and Subatomic Physics Research
- Thin-Film Transistor Technologies
- Electrostatic Discharge in Electronics
- Magnetic Field Sensors Techniques
- Diamond and Carbon-based Materials Research
- Non-Destructive Testing Techniques
- Quantum chaos and dynamical systems
Cornell University
2023-2024
Weill Cornell Medicine
2023-2024
General Atomics (United States)
2013-2022
Erasmus University Rotterdam
2021
Erasmus MC
2021
Texas Advanced Computing Center
2021
University of California, San Diego
2001-2020
Fusion for Energy
2013
Forschungszentrum Jülich
2008-2011
University of California, Los Angeles
2009-2010
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...
Progress in the definition of requirements for edge localized mode (ELM) control and application ELM methods both high fusion performance DT operation non-active low-current ITER is described. Evaluation power fluxes low plasma current H-modes shows that uncontrolled ELMs will not lead to damage tungsten (W) divertor target, unlike high-current which by expected. Despite lack at lower currents, found be required under these conditions prevent an excessive contamination W, could eventually...
Intermittent plasma objects (IPOs) featuring higher pressure than the surrounding plasma, and responsible for ∼50% of E×BT radial transport, are observed in scrape off layer (SOL) edge DIII-D tokamak [J. Watkins et al., Rev. Sci. Instrum. 63, 4728 (1992)]. Conditional averaging reveals that IPOs, produced at a rate ∼3×103 s−1, positively charged also polarized, poloidal electric fields up to 4000 V/m. The IPOs move poloidally speeds 5000 m/s radially with E×BT/B2 velocities ∼2600 near last...
Intermittent plasma objects (IPOs), featuring higher pressure than the surrounding plasma, are responsible for ∼50% of E×BT radial transport in scrape off layer (SOL) Doublet III D (DIII-D) tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] L- and H-mode discharges. Conditional averaging reveals that IPOs positively charged feature internal poloidal electric fields up to 4000 V/m. The move radially with E×BT/B2 velocities ∼2600 m/s near last closed flux surface (LCFS), ∼330 wall. slow down...
As part of the ITER Design Review and in response to issues identified by Science Technology Advisory Committee, physics requirements were reviewed as appropriate updated. The focus this paper will be on recent work affecting design with special emphasis topics near-term procurement arrangements. This describe results on: sensitivity studies, poloidal field coil requirements, vertical stability, effect toroidal ripple thermal confinement, material choice heat load for plasma-facing...
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,...
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...
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....
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...
Abstract The non-linear reduced four-field RMHD model in cylindrical geometry was extended to include plasma rotation, neoclassical poloidal viscosity and two fluid diamagnetic effects. Interaction of the static resonant magnetic perturbations (RMPs) with rotating plasmas tokamaks studied. self-consistent evolution equilibrium electric field due RMP penetration is taken into account model. It demonstrated that pedestal region steep pressure gradients, mean flows perpendicular field, which...
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...
As the finalization of a hydrogen experiment towards deuterium phase, exploration best performance plasma was intensively performed in large helical device. High ion and electron temperatures, Ti Te, more than 6 keV were simultaneously achieved by superimposing high-power cyclotron resonance heating onneutral beam injection (NBI) heated plasma. Although flattening temperature profile core region observed during discharges, one could avoid degradation increasing density. Another key parameter...
Controlling the boundary layer in fusion-grade, high-performance, plasma discharges is essential for successful development of toroidal magnetic confinement power generating systems. A promising approach controlling based on use small, externally applied, edge resonant perturbation (RMP) fields (). long-term focus area tokamak fusion research has been to find methods, involving non-axisymmetric perturbations reduce intense particle and heat fluxes wall. Experimental RMP progressed from early...
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...
High-pressure gas-jet injection of neon and argon is shown to be a simple robust method mitigate the deleterious effects disruptions on DIII-D tokamak. The gas jet penetrates central plasma at its sonic velocity. deposited species dissipates >95% by radiation substantially reduces mechanical stresses vessel caused poloidal halo currents. species-charge distribution can include >50% fraction neutral which inhibits runaway electrons. favorable scaling this technique burning fusion plasmas discussed.
Large Type-I edge-localized mode (ELM) heat pulses may limit the life of divertor targets in a burning plasma. Recent experiments show that pitch-resonant nonaxisymmetric magnetic perturbations plasma edge 0.0005 or less main field offer useful solution, but there is little room presently designed ITER for even small perturbation coils. We present proposed coil requirements ELM suppression, derived primarily from DIII-D suppression experiments. by calculated examples large arrays coils (e.g....
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...