A5045430789- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Extremum Seeking Control Systems
- Laser-Plasma Interactions and Diagnostics
- Theoretical and Computational Physics
- Atomic and Subatomic Physics Research
- High-Energy Particle Collisions Research
- Microwave Engineering and Waveguides
- Combustion and flame dynamics
- Diamond and Carbon-based Materials Research
- Flow Measurement and Analysis
- Physics of Superconductivity and Magnetism
- Turbomachinery Performance and Optimization
- Geomagnetism and Paleomagnetism Studies
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- Earthquake Detection and Analysis
- Antenna Design and Optimization
- Quantum and electron transport phenomena
General Atomics (United States)
2024
Soonchunhyang University
2024
Princeton Plasma Physics Laboratory
2019-2022
Los Alamos National Laboratory
2022
Royal Military Academy
2020
Seoul National University
2011-2019
Princeton University
2019
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...
Abstract This work presents a model for predicting electron energy gain from cyclotron (EC) wave-particle interactions during the breakdown phase of tokamak pre-ionization. Investigation this to infer EC requirements inevitably demands high-fidelity simulation study covering gas physics, plasma dynamics, and absorption. Under significantly low density temperature, electrons interact nonlinearly with wave which picture is distinct linear or quasilinear heating. For room temperature electrons,...
An Electron Cyclotron Emission (ECE) modeling code has been developed to model ECE radiation with an arbitrary electron momentum distribution, a small oblique angle, both ordinary (O-mode) and extraordinary polarizations (X-mode), multiple cyclotron frequency harmonics. The emission absorption coefficients are calculated using the Poynting theorem from cold plasma dispersion electron–microwave interaction full anti-Hermitian tensor. shows several signatures that can be used diagnose...
Abstract A tokamak, a torus-shaped nuclear fusion device, needs an electric current in the plasma to produce magnetic field poloidal direction for confining plasmas. Plasma is conventionally generated by electromagnetic induction. However, steady-state reactor, minimizing inductive essential extend tokamak operating duration. Several non-inductive drive schemes have been developed operations such as radio-frequency waves and neutral beams. commercial reactors require minimal use of these...
Abstract Although gas breakdown phenomena have been intensively studied over 100 years, the mechanism in a strongly magnetized system, such as tokamak, has still obscured due to complex electromagnetic topologies. There widespread misconception that conventional model of unmagnetized system can be directly applied system. However, we found clear evidence existing theories cannot explain experimental results. Here, demonstrate underlying tokamaks, turbulent ExB mixing avalanche, which...
ECH-assisted start-up using trapped particle configuration (TPC) is firstly studied in a superconducting, conventional tokamak, KSTAR. First, improved and efficient TPC than field null (FNC) achieved by enhanced pre-ionization plasma quality. shows the broader operation window terms of poloidal quality deuterium prefill pressure that FNC. Surprisingly trapping enhances performance even with much lower ratio spherical torus. Reliability low investigated 0D evolution code, TECHP0D. Second,...
Abstract Among various edge localized mode (ELM) crash control methods, only non-axisymmetric magnetic perturbations (NAMPs) yield complete suppression of ELM crashes beyond their mitigation, and thus attract more attention than others. No other devices except KSTAR, DIII-D, recently EAST have successfully achieved with NAMPs. The underlying physics mechanisms these successful suppressions in a field environment, however, still remain uncertain. In this work, we investigate the...
Diffusive transport processes in magnetized plasmas are highly anisotropic, with fast parallel along the magnetic field lines sometimes faster than perpendicular by orders of magnitude. This constitutes a major challenge for describing non-grid-aligned structures Eulerian (grid-based) simulations. The present paper describes and validates new method diffusion based on anti-symmetry representation [Halpern Waltz, Phys. Plasmas 25, 060703 (2018)]. In formalism, manifests as flow operator...
Global gyrokinetic simulations with self-consistent coupling of neoclassical and turbulent dynamics show that turbulence can significantly affect plasma self-driven mean current generation in tokamaks. The amplitude, profile associated phase space structures all be modified. Turbulence reduce the collisionless regime, generate corrugation near rational magnetic surface nonlocally drive linearly stable region—all these are expected to have a radical impact on broad tokamak physics. Both...
The maser instability associated with the loss-cone distribution has been widely invoked to explain radio bursts observed in astrophysical plasma environment, such as aurora and corona. In laboratory of a tokamak, events reminiscent these have also frequently an electron cyclotron emission (ECE) burst microwave range ( $\mathrm{\sim }2{f_{\textrm{ce}}}$ near last closed flux surface) during transient magnetohydrodynamic events. These short duration ~10 μs display radiation spectrum...
We report that the control of 'island width growth rate', which is defined as dW/dt, more efficient than width' for neoclassical tearing mode stabilization using minimum seeking method. A concept island rate method newly proposed real-time feedback by electron cyclotron current drive. To evaluate performance concept, predictive simulations with an integrated numerical system are performed based on two types controllers; first a finite difference controller and second sinusoidal perturbation...
The thermal quench triggered by locked modes is known to be mainly due open stochastic magnetic field lines connected the wall boundary. It essential understand 3D structure of since it determines overall plasma dynamics in system. In this study, we analyze topology for two key concepts, connection length Lc and effective mirror ratio Meff, present a comprehensive picture electron ion related topology. ambipolar potential, sharp potential drop across distinct regions induces E × B transport...
Abstract An experimental scan of the electron cyclotron waves (EC) toroidal injection angle in plasma breakdown is performed at DIII-D tokamak. The second harmonic, extraordinary mode EC used for study. dependence n e and T on cannot be conclusively drawn from this study due to large error bars measurements. On other hand, high data points are observed some discharges which can explained by nonlinear heating. D α emission measurement shows a clear relation between time angle. investigation...
Abstract Magnetic island perturbations may cause a reduction in plasma self-driven current that is needed for tokamak operation. A novel effect on revealed by global gyrokinetic simulations due to magnetic-island-induced 3D electric potential structures, which have the same dominant mode numbers as of magnetic island, whereas centered at both inner and outer edge island. The non-resonant islands are shown drive through an efficient nonlinear parallel acceleration electrons. In large aspect...
Recently, the numerical scheme presented by Mishchenko et al. [Phys. Plasmas 21, 052113 (2014); 092110 (2014)] enabled explicit gyrokinetic simulations of low-frequency electromagnetic instabilities in tokamaks at experimentally relevant values plasma β. This resolved long-standing cancellation problem that previously hindered particle-in-cell code magnetohydrodynamic phenomena with inherently small parallel electric fields. Moreover, did not employ approximations eliminate critical...
The Thomson scattering system has been recently installed on Versatile Experiment Spherical Torus (VEST) to measure the electron temperature and density of core plasmas. Since calibration is required for accurate measurement these parameters, a polychromator efficiency are calibrated. bias voltage detector optimized relative responsivity measured analyse spectral broadening. tendency decreasing because ambient change addressed together. efficiencies alignments using HeNe laser Nd:YAG...