A5054609322- 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
- Nuclear Physics and Applications
- Nuclear Materials and Properties
- Solar and Space Plasma Dynamics
- Combustion and Detonation Processes
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Electrostatic Discharge in Electronics
- Electron and X-Ray Spectroscopy Techniques
- Advanced Data Storage Technologies
- Nuclear Engineering Thermal-Hydraulics
- Semiconductor materials and devices
- Particle Detector Development and Performance
- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Geomagnetism and Paleomagnetism Studies
- Natural Language Processing Techniques
- Silicon Carbide Semiconductor Technologies
- High-Velocity Impact and Material Behavior
Fiat Lux
2020-2024
General Atomics (United States)
2008-2021
University of California, San Diego
2011-2020
Huazhong University of Science and Technology
2019
Institute of Plasma Physics
2019
Chinese Academy of Sciences
2019
Chengdu University
2019
Japan External Trade Organization
2014
Culham Centre for Fusion Energy
2013
Columbia University
2013
One modeling framework for integrated tasks (OMFIT) is a comprehensive which has been developed to enable physics codes interact in complicated workflows, and support scientists at all stages of the cycle. The OMFIT development follows unique bottom-up approach, where design capabilities organically evolve progressive integration components that are required accomplish goals increasing complexity. provides workflow easily generating full kinetic equilibrium reconstructions constrained by...
The SPARC tokamak is a critical next step towards commercial fusion energy. designed as high-field ( $B_0 = 12.2$ T), compact $R_0 1.85$ m, $a 0.57$ m), superconducting, D-T with the goal of producing gain $Q>2$ from magnetically confined plasma for first time. Currently under design, will continue path Alcator series tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in device. achievable conservative...
An overview of the present status research toward final design ITER disruption mitigation system (DMS) is given. The DMS based on massive injection impurities, in order to radiate plasma stored energy and mitigate potentially damaging effects disruptions. this will be extremely challenging due many physics engineering constraints such as limitations port access amount species injected impurities. Additionally, questions relevant remain unsolved mechanisms for mixing assimilation impurities...
Abstract The SPARC tokamak project, currently in engineering design, aims to achieve breakeven and burning plasma conditions a compact device, thanks new developments high-temperature superconductor technology. With magnetic field of 12.2 T on axis 8.7 MA current, is predicted produce 140 MW fusion power with gain Q ≈ 11, providing ample margin respect its mission > 2. All systems are being designed this landmark discharge, thus enabling the study physics operations reactor relevant pave...
DIII-D experiments on rapid shutdown runaway electron (RE) beams have improved the understanding of processes involved in RE beam control and dissipation. Improvements feedback enabled stable confinement out to volt-second limit ohmic coil, as well enabling a ramp down zero current. Spectroscopic studies shown that neutrals tend be excluded from centre. Measurements energy distribution function indicate broad with mean order several MeV peak energies 30–40 MeV. The appears more skewed...
The object of this review is to summarize the achievements research on Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] place that in context quest for practical fusion energy. a compact, high-field tokamak, whose unique design operating parameters have produced wealth new important results since it began operation 1993, contributing data extends tests critical physical models into parameter ranges regimes. Using only...
MHD simulations of rapid shutdown scenarios by massive particle injection in DIII-D, Alcator C-Mod and ITER are performed order to study runaway electron (RE) transport during mitigated disruptions. The include a RE confinement model using drift-orbit calculations for test particles. A comparison limited diverted plasma shapes is studied DIII-D simulations, improved the shape found due both spatial localization reduced toroidal spectrum nonlinear activity. compare which impurity (Ar)...
With the installation of non-axisymmetric coil systems on major tokamaks for purpose studying prospects ELM-free operation, understanding plasma response to applied fields is a crucial issue. Application different models, using standard tools, DIII-D discharges with from internal coils, shown yield qualitatively results. The can be treated as an initial value problem, following system dynamically unperturbed state, or nearby perturbed equilibrium approach, and both linear nonlinear models...
New rapid shutdown strategies have been recently tested in the DIII-D tokamak to mitigate runaway electrons (REs). Disruptions ITER are predicted generate multi-MeV REs that could damage machine. The RE population large tokamaks is expected be dominated by avalanche amplification which can mitigated at high density levels collisional drag. Particle injection schemes for suppression of developed and ITER-relevant scenarios: massive gas injection, shattered pellet (SPI) shell injection....
SPARC is being designed to operate with a normalized beta of $\beta _N=1.0$ , density $n_G=0.37$ and safety factor $q_{95}\approx 3.4$ providing comfortable margin their respective disruption limits. Further, low poloidal _p=0.19$ at the $q=2$ surface reduces drive for neoclassical tearing modes, which together frozen-in classically stable current profile might allow access robustly tearing-free operating space. Although inherent stability expected reduce frequency disruptions, loading...
High-pressure noble gas jet injection is a mitigation technique which potentially satisfies the requirements of fast response time and reliability, without degrading subsequent discharges. Previously reported experiments on DIII-D showed good success at reducing deleterious disruption effects. In this paper, results recent Alcator C-Mod are reported. Jointly, these have greatly improved understanding dynamics processes involved in mitigating both machines, sequence events following observed...
Disruption mitigation experiments using massive gas injection (MGI) on Alcator C-Mod [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] and DIII-D [Luxon Davis, Fusion Technol. 8, 441 (1985)] have shown that magnetohydrodynamics (MHD) plays an important role. The three-dimensional MHD code NIMROD [Sovinec J. Comput. 195, 355 (2004)] has been extended to include atomic physics taken from the KPRAD perform simulations of MGI. Considerable benchmarking done against for neon helium jet...
Experiments have been performed in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] toward understanding runaway electron formation and amplification during rapid discharge shutdown, as well achieving complete collisional suppression of these electrons via massive delivery impurities. Runaway acceleration appear to be explained using zero-dimensional (0D) current quench toroidal electric field. 0D or even one-dimensional modeling a Dreicer seed term, however, appears too small...
Simulations of neon massive gas injection into DIII-D are performed with the 3D MHD code NIMROD. The poloidal and toroidal distribution impurity source is varied. This report will focus on effects variation mixing radiated power asymmetry. Even toroidally symmetric found to produce asymmetric due convective heat flux produced by 1/1 mode. When localized, phase relationship between mode location important, affecting both radiation peaking mixing. Under certain circumstances, a single,...
Locked modes are known to be one of the major causes disruptions, but physical mechanisms by which locking leads disruptions not well understood. Here we analyze evolution temperature profile in presence multiple coexisting locked during partial and full thermal quenches. Partial quenches often observed an initial, distinct stage quench. Near onset quenches, island O-points align with each other on midplane, their widths sufficient overlap other, as indicated Chirikov parameter. Energy...
The potential formation of multi-mega-ampere beams relativistic "runaway" electrons (REs) during sudden terminations tokamak plasmas poses a significant challenge to the tokamak's development as fusion energy source. Here, we use state-of-the-art modeling disruption magnetohydrodynamics coupled with self-consistent evolution RE generation and transport show that non-axisymmetric in-vessel coil will passively prevent beam disruptions in SPARC tokamak, compact, high-field, high-current device...
The operation of a 3D coil--passively driven by the current quench loop voltage--for deconfinement runaway electrons is modeled for disruption scenarios in SPARC and DIII-D tokamaks. Nonlinear MHD modeling carried out with NIMROD code including time-dependent magnetic field boundary conditions to simulate effect coil. Further some cases uses ASCOT5 calculate advection diffusion coefficients based on NIMROD-calculated fields, DREAM compute evolution presence these transport coefficients....
Nonlinear magnetohydrodynamic simulations of an equilibrium in the DIII-D geometry with applied resonant magnetic perturbations (RMPs) are performed. The reduction pedestal density observed RMP experiments is explained terms E × B convection cells crossing separatrix. Results obtained both absence plasma rotation and for two profiles having different values at effects on screening as well transport mechanism from simulations. Poloidal mode spectra show amplification components error field...
Simulations of massive gas injection for disruption mitigation in DIII-D are carried out to compare the toroidal peaking radiated power cases one and two jets. The radiation factor (TPF) results from a combination distribution impurities heat flux associated with mode. When ignoring effects strong uni-directional neutral beam rotation present experiment, injected found spread helically along field lines preferentially toward high-field-side, which is explained terms nozzle equation....
The first successful results on the transfer of a coaxial helicity injection (CHI) produced discharge to inductive operation are reported. CHI-assisted plasma startup is more robust than only operation. After hand off for operation, initial 90 kA CHI-produced current drops 40 kA, then ramps up 170 using 30 mV s, 30% higher that by induction alone. These significant performance enhancing were obtained HIT-II spherical torus experiment (major/minor radius 0.3/0.2 m).
Damaging effects of disruptions are a major concern for Alcator C-Mod, ITER and future tokamak reactors. High-pressure noble gas jet injection is mitigation technique which potentially satisfies the operational requirements fast response time reliability, while still being benign to subsequent discharges. Disruption experiments using an optimized system carried out on C-Mod study physics penetration into high pressure plasmas, as well ability impurities convert plasma energy radiation...
The injection of a high pressure jet noble gas is one possible approach to mitigating potential disruption damage tokamaks. efficacy this given only modest penetration the gas-jet into plasma particular concern in absolute device, like Alcator C-Mod (Hutchinson I.H. et al 1994 Phys. Plasmas 1 1511) or ITER. To investigate effectiveness various depths, simple radiation model based on corona equilibrium assumption employed resistive magnetohydrodynamic (MHD) simulations an plasma....
Mixed gases are used for massive gas injection disruption mitigation on Alcator C-Mod in order to optimize radiation efficiency, halo current reduction and response time. Gas mixtures of helium argon (argon fraction 0–50%) investigated detail, as well deuterium, argon, krypton helium. Experiments show that injecting He/Ar leads faster thermal quenches than with pure or injection, thus improving the time system reducing current. Small fractions (∼5–10%) also lead optimized large electron...