A5021447616- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Nuclear Materials and Properties
- Laser-induced spectroscopy and plasma
- Particle accelerators and beam dynamics
- Ion-surface interactions and analysis
- Atomic and Molecular Physics
- Metal and Thin Film Mechanics
- Superconducting Materials and Applications
- Fluid Dynamics and Turbulent Flows
- Dust and Plasma Wave Phenomena
- Semiconductor materials and devices
- Atomic and Subatomic Physics Research
- Laser Design and Applications
- Diamond and Carbon-based Materials Research
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Geomagnetism and Paleomagnetism Studies
- Plasma Applications and Diagnostics
- High-pressure geophysics and materials
- Characterization and Applications of Magnetic Nanoparticles
University of California, San Diego
2016-2025
Southwestern Institute of Physics
2017-2021
Molina Center for Energy and the Environment
2011-2020
Swarthmore College
2019
Jacobs (United States)
2001-2018
University of York
2017
University of Wisconsin–Madison
1996-2016
West Virginia University
2016
Center for Urban Waters
2015
Dutch Institute for Fundamental Energy Research
2014
A number of analyses, meta-analyses, and assessments, including those performed by the Intergovernmental Panel on Climate Change, National Oceanic Atmospheric Administration, Renewable Energy Laboratory, International Agency, have concluded that deployment a diverse portfolio clean energy technologies makes transition to low-carbon-emission system both more feasible less costly than other pathways.In contrast, Jacobson et al.[Jacobson MZ, Delucchi MA, Cameron
Laser wakefield acceleration of electrons holds great promise for producing ultracompact stages GeV scale, high-quality electron beams applications such as x-ray free lasers and high-energy colliders. Ultrahigh intensity laser pulses can be self-guided by relativistic plasma waves (the wake) over tens vacuum diffraction lengths, to give >1 energy in centimeter-scale low density plasmas using ionization-induced injection inject charge into the wake even at densities. By restricting a distinct...
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...
The paradigm of shear suppression turbulence as the mechanism for low to high confinement mode (L H) transition is examined by quantitative comparison predictions with experimental results from DIII-D tokamak [Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159]. L H trigger V×B rotation, not main ion pressure gradient. radial electric field Er increases before fluctuation suppression, consistent increasing cause suppression. spatial...
Zonal flows, which means azimuthally symmetric band-like shear are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows a key constituent virtually all cases regimes of drift wave turbulence, indeed, so much this classic problem frequently referred to as “drift wave-zonal flow turbulence.” In review, new viewpoints unifying concepts presented, facilitate understanding physics, via theory, computation their confrontation with results laboratory...
A quasiperiodic Er oscillation at a frequency of <4 kHz, much lower than the geodesic-acoustic-mode frequency, with modulation in edge turbulence preceding and following low-to-high (L-H) confinement mode transition, has been observed for first time EAST tokamak, using two toroidally separated reciprocating probes. Just prior to L-H often evolves into intermittent negative spikes. The low-frequency oscillation, as well spikes, is strongly correlated turbulence-driven Reynolds stress, thus...
A fast edge turbulence suppression event has been simulated in the electrostatic version of gyrokinetic particle-in-cell code XGC1 a realistic diverted tokamak geometry under neutral particle recycling. The results show that sequence turbulent Reynolds stress followed by neoclassical ion orbit-loss driven together conspire to form sustaining radial electric field shear and quench transport just inside last closed magnetic flux surface. main action is located thin layer around ψN≃0.96–0.98,...
Policy makers are increasingly focused on strategies to decentralize the electricity grid. We analyze business model for one mode of decentralization—microgrids—and quantify economics self-supply and thermal energy explicitly resolve technological as well policy variables. offer a tool, based Distributed Energy Resources Customer Adoption Model (DER-CAM) modeling framework, that determines cost-minimal capacity operation distributed resources in microgrid, apply it southern California three...
The nonlinear coupling between small scale high-frequency turbulence and larger lower-frequency fluctuations increases transiently in transitions to improved confinement the DIII-D tokamak. This increase starts before rapid suppression E x B shear-flow development region that becomes H-mode transport barrier/shear flow region. After transition, returns L-mode levels. These results are consistent with expectations for spontaneous triggered by a turbulence-driven sheared flow.
An azimuthally symmetric radially sheared plasma fluid flow is observed to spontaneously form in a cylindrical magnetized helicon device with no external sources of momentum input. A turbulent conservation analysis shows that this shear sustained by the Reynolds stress generated collisional drift turbulence device. The results provide direct experimental support for basic theoretical picture drift-wave-shear-flow interactions.
The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens door to a new level core turbulence model validation. Toward this end, implementation synthetic that physical beam emission spectroscopy and correlation electron cyclotron is presented. Initial results from their applications local gyrokinetic simulations two locations in L-mode discharge performed with GYRO code Candy R. E. Waltz, J....
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 Y. Hirooka, R. W. Conn, T. Sketchley, K. Leung, G. Chevalier, Doerner, J. Elverum, D. M. Goebel, Gunner, Khandagle, B. Labombard, Lehmer, P. Luong, Ra, L. Schmitz, Tynan; A new plasma‐surface interactions research facility: PISCES‐B first materials erosion experiments on bulk‐boronized graphite. Journal of...
The present status of experiments on zonal flows in magnetic confinement is examined. innovative use traditional and modern diagnostics has revealed unambiguously the existence flows, their spatio-temporal characteristics, relationship to turbulence effects confinement. In particular, a number observations have been accumulated oscillatory branch named geodesic acoustic modes, suggesting necessity for theories give proper description. addition these basic properties several new methods...
Experimental results from a magnetized argon plasma column demonstrate controlled transition to turbulent state as the magnetic field (B) strength is increased. At lower B there an onset of fluctuations in density and potential. These are shown be due drift waves that have been modified by flow shear. As increased character undergoes several changes. changes include general decrease coherence, increase phase lag (between potential), straightening observed dispersion relation. Concomitantly,...
For the first time, profiles (0.3&lt;ρ&lt;0.9) of electron temperature and density fluctuations in a tokamak have been measured simultaneously results compared to nonlinear gyrokinetic simulations. Electron neutral beam-heated, sawtooth-free low confinement mode (L-mode) plasmas DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] are found be similar frequency normalized amplitude, with amplitude increasing radius. The radial profile two fluctuation fields allows for new rigorous...
The absolute rate of nonlinear energy transfer among broadband turbulence, low-frequency zonal flows (ZFs) and geodesic acoustic modes (GAMs) was measured for the first time in fusion-grade plasmas using two independent methods across a range heating powers. results show that turbulent kinetic from intermediate frequencies (20--80 kHz) transferred into ZFs GAMs, as well fluctuations at higher ($>80\text{ }\text{ }\mathrm{kHz}$). As power increased, turbulence GAMs GAM amplitudes peaked then...
Transport barrier formation and its relation to sheared flows in fluids plasmas are of fundamental interest various natural laboratory observations critical importance achieving an economical energy production a magnetic fusion device. Here we report the first observation edge transport event gyrokinetic simulation carried out realistic tokamak geometry. The results show that turbulent Reynolds stress driven ExB act concert with neoclassical orbit loss quench form just inside last closed...
A cylindrically symmetric (azimuthal mode number m=0) resonant inductive (MO/RITM) radio frequency (rf) helicon wave high density plasma source is described. The consists of an antenna and bell jar generator immersed in a diverging magnetic field. Plasma generated this upstream region then transported along the field lines into low-field downstream processing chamber. propagating observed with rf spatial distribution propagation characteristics that obey theoretical m=0 dispersion relation....
Large-scale steady-state convection is found to dominate the particle transport just inside last closed flux surface (LCFS) in Ohmic discharges CCT tokamak. Near limiter radius and scrape-off layer, fluctuation-induced prevalent. At L-H transition, pattern near LCFS disrupted a more poloidally symmetric, near-sonic plasma flow develops. Convective turbulent are reduced across entire edge region, resulting formation of H-mode barrier.
We present a direct measurement of the quenching nonlocal heat transport in laser-produced plasma by applying large external magnetic fields (>10 T). The temporally resolved Thomson-scattering measurements electron temperature profile show that front propagation transverse to high-power laser beam is slowed resulting extremely strong local heating. find agreement with hydrodynamic modeling when including field model self-consistently evolves plasma.
The levels of retention in codeposited layers each the three ITER materials (C, Be and W) are compared. Scaling laws, based on conditions during codeposition process (surface temperature, incident particle energy ratio depositing fluxes), presented to allow prediction expected under conditions. Retention carbon codeposits scales inversely with energy, whereas metallic level proportionally increasing energy. differing scaling provides insights into which material may impact global depending...
Validation of models pedestal structure is an important part predicting height and performance in future tokamaks. The Thomson scattering diagnostic at DIII-D has been upgraded support validating these models. Spatial temporal resolution, as well signal to noise ratio, have all specifically enhanced the region. This region now diagnosed by 20 view-chords with a spacing 6 mm length just under 5 sampled nominal rate 250 Hz. When mapped outboard midplane, this corresponds ~3 spacing. These...
We report experimental studies demonstrating a controlled transition to fully developed broadband turbulence in an argon helicon plasma linear device. show the detailed dynamics during from nonlinearly coupled but distinct eigenmodes at low magnetic fields larger fields. As field (B) is increased B ∼ 40 mT, initially we observe slow smooth changes of system (to 140 mT), followed by sharp (within ∼10 mT) centrally peaked narrow density profiles, strong edge potential gradients and pronounced...