A5062037694- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Semiconductor materials and devices
- Nuclear Physics and Applications
- Advanced Data Storage Technologies
- Laser-induced spectroscopy and plasma
- Solar and Space Plasma Dynamics
- Advancements in Semiconductor Devices and Circuit Design
- Nuclear Materials and Properties
- Atomic and Molecular Physics
- Electron and X-Ray Spectroscopy Techniques
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Fault Detection and Control Systems
- Thin-Film Transistor Technologies
- Ion-surface interactions and analysis
- Silicon and Solar Cell Technologies
- Physics of Superconductivity and Magnetism
- Computational Physics and Python Applications
General Atomics (United States)
2016-2025
CEA Cadarache
2021
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2021
University of California, Los Angeles
2021
Predictive Science (United States)
2019
Max Planck Institute for Plasma Physics - Greifswald
2018
Princeton University
2018
University of California, San Diego
2018
Oak Ridge National Laboratory
2018
Oak Ridge Associated Universities
2018
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...
Abstract Shattered pellet injection (SPI) is one of the prime candidates for ITER disruption mitigation system because its deeper penetration and larger particle flux than massive gas (MGI) (Taylor et al 1999 Phys. Plasmas 6 1872) using deuterium (Commaux 2010 Nucl. Fusion 50 112001, Combs IEEE Trans. Plasma Sci . 38 400, Baylor 2009 49 085013). The will likely use mostly high Z species such as neon more effective thermal pumping constraints on maximum amount or helium that could be...
Using data-driven methodology, we exploit the time series of relevant plasma parameters for a large set disrupted and non-disrupted discharges to develop classification algorithm detecting disruptive phases in shots that eventually disrupt. Comparing same methodology on different devices is crucial order have information portability developed possible extrapolation ITER. Therefore, use data from two very tokamaks, DIII-D Alcator C-Mod. We focus subset disruption predictors, most which are...
This paper reports on disruption prediction using a shallow machine learning method known as random forest, trained large databases containing only plasma parameters that are available in real-time Alcator C-Mod, DIII-D, and EAST. The database for each tokamak contains sampled ∼106 times throughout ∼104 discharges (disruptive non-disruptive) over the last four years of operation. It is found number (e.g. , ) exhibit changes aggregate approached one or more these tokamaks. However, machine,...
For the first time it is experimentally demonstrated on JET tokamak that a combination of low impurity concentration bulk plasma and large magnetohydrodynamic instabilities able to suppress relativistic electron beams without measurable heat loads onto facing components. Magnetohydrodynamic simulations instability modeling postinstability confirm prompt loss runaways absence regeneration during final current collapse. These surprising findings motivate new approach dissipate runaway...
Operating experimental devices have provided key inputs to the design process for ITER axisymmetric control. In particular, experiments quantified controllability and robustness requirements in presence of realistic noise disturbance environments, which are difficult or impossible characterize with modelling simulation alone. This kind information is particularly critical vertical control, poses highest demands on poloidal field system performance, since consequences loss control can be...
Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated recent research worldwide.Recent analysis has identified the current density profile as main drive disruptive instabilities simulating ITER's baseline scenario with low external torque.Ongoing development model-based active magnetohydrodynamic is improving stability multiple scenarios.Significant advances made toward physicsbased prediction...
A multi-device database of disruption characteristics has been developed under the auspices International Tokamak Physics Activity magneto-hydrodynamics topical group. The purpose this ITPA (IDDB) is to find commonalities between and mitigation in a wide variety tokamaks order elucidate physics underlying tokamak disruptions extrapolate toward much larger devices, such as ITER future burning plasma devices. In contrast previous smaller data collation efforts, IDDB aims provide significant...
Injection of large shattered pellets composed variable quantities the main ion species (deuterium) and high-Z impurities (neon) in DIII-D tokamak demonstrates control thermal quench (TQ) current (CQ) properties mitigated disruptions. As pellet composition is varied, TQ radiation fractions increase continuously with quantity radiating impurity pellet, a corresponding decrease divertor heating. Post-TQ plasma resistivities as result higher fraction, allowing decay timescales based on...
Realization of a high-current (approaching 1 MA) post-disruption runaway electron (RE) beam in DIII-D yields controlled access to very low edge safety factor (qa) conditions. This enables unique observation and study low-order kink instabilities plasmas where the current is carried entirely by relativistic REs. The conventional external stability boundary (in terms qa internal inductance, ℓi) found accurately predict operational space RE beam, with limited ≈2. Kink appear characteristic...
Abstract A series of experiments have been executed at JET to assess the efficacy newly installed shattered pellet injection (SPI) system in mitigating effects disruptions. Issues, important for ITER disruption mitigation system, such as thermal load mitigation, avoidance runaway electron (RE) formation, radiation asymmetries during quench electromagnetic control and RE energy dissipation addressed over a large parameter range. The efficiency has examined various SPI strategies. paper...
Since the successful first plasma generation in middle of 2008, three experimental campaigns were successfully made for KSTAR device, accompanied with a necessary upgrade power supply, heating, wall-conditioning and diagnostic systems. was operated toroidal magnetic field up to 3.6 T circular shaped plasmas current 700 kA pulse length 7 s, have been achieved limited capacity PF magnet supplies. The mission program is achieve steady-state operations high performance relevant ITER future...
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....
Extremely low density operation free of error field penetration supports the excitation trace-level quiescent runaway electron (RE) populations during flat-top DIII-D Ohmic discharges. Operation in regime allows accurate measurement all key parameters important to RE excitation, including internal broadband magnetic fluctuation level. onset is characterized and found be consistent with primary (Dreicer) generation rates. Impurity-free collisional suppression population investigated by...
The evolution of the runaway electron (RE) energy distribution function fε during massive gas injection into centered post-disruption plateaus has been reconstructed. Overall, is found to be much more skewed toward low than predicted by avalanche theory. reconstructions also indicate that RE pitch angle θ not uniform, but tends large at energies and small ∼ 0.1–0.2 high energies. Overall power loss from plateau appears dominated collisions with background free bound electrons, leading line...
Novel spatial, temporal, and energetically resolved measurements of bremsstrahlung hard-x-ray (HXR) emission from runaway electron (RE) populations in tokamaks reveal nonmonotonic RE distribution functions whose properties depend on the interplay electric field acceleration with collisional synchrotron damping. Measurements are consistent theoretical predictions momentum-space attractors that accumulate electrons. measured to shift a higher energy when force is reduced by decreasing toroidal...
A decade-long operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) has contributed significantly to superconducting tokamak devices and advancement physics which will be beneficial for ITER K-DEMO programs. Even with limited heating capability, various conventional as well new operating regimes have been explored achieved improved performance. As examples, a long pulse high-confinement mode without an edge-localized (ELM) crash was over 70 30 s, respectively. The unique...
We report on the first demonstration of dissipation fully avalanched post-disruption runaway electron (RE) beams by shattered pellet injection in DIII-D tokamak. Variation injected species shows that depends strongly mixture, while comparisons with massive gas do not show a significant difference between pellets or gas, suggesting is rapidly ablated relativistic electrons before radial penetration into beam can occur. Pure dominantly neon increases RE current through pitch-angle scattering...
Relativistic electron (RE) beams at high current density (low safety factor, qa) yet very low free-electron accessed with D2 secondary injection in the DIII-D and JET tokamak are found to exhibit large-scale MHD instabilities that benignly terminate RE beam. In JET, this technique has enabled termination of MA-level currents without measurable first-wall heating. This scenario thus offers an unexpected alternate pathway achieve mitigation collisional dissipation. Benign is explained by two...
Abstract A relativistic electron probe has been developed in the DIII-D tokamak, capable of simultaneously resolving pitch angles and energies runaway electrons (REs) for first time. Due to speeds REs, their gyro-orbit size becomes comparable those fast deuterium with tens keV range. This allows measurement RE strike images on a phosphor plane, orbits being deflected by Lorentz force as they pass through pinhole aperture. The positions correspond incident REs. Monte Carlo N-Particle...
Abstract Plasma disruptions present a significant challenge to the viability of fusion energy production in tokamak reactors. Among disruption mitigation techniques, shattered pellet injection (SPI) has emerged as promising approach. The results presented this paper show novel findings impact nitrogen and neon seeding on sequence following SPI Joint European Torus (JET). This study exposes an order magnitude reduction pre-thermal quench duration for highly seeded plasmas pure deuterium SPI,...
A particle balance analysis was conducted during a deuterium (D2) shattered pellet injection-induced plasma shutdown on the DIII-D tokamak to determine why less than 20% of material is assimilated into core by mid-current quench (CQ). Initially, most D2 injected as frozen shards and ionized upon entering vessel. During thermal quench, particles move divertors subsequently center post (CP) walls, where they rapidly recycle partially accumulate neutrals without assimilating plasma. In...
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...
Since the first H-mode discharges in 2010, duration of state has been extended and a significantly wider operational window plasma parameters attained. Using second neutral beam (NB) source improved tuning equilibrium configuration with real-time control, stored energy Wtot ∼ 450 kJ achieved corresponding confinement time τE 163 ms. Recent discharges, produced fall 2012, have reached βN up to 2.9 surpassed n = 1 ideal no-wall stability limit computed for pressure profiles, which is one key...