A5020627604- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Multimedia Communication and Technology
- Superconducting Materials and Applications
- Analog and Mixed-Signal Circuit Design
- Gyrotron and Vacuum Electronics Research
- Low-power high-performance VLSI design
- Radio Frequency Integrated Circuit Design
- Advanced DC-DC Converters
- Video Analysis and Summarization
- Advancements in Semiconductor Devices and Circuit Design
- Caching and Content Delivery
- IoT and Edge/Fog Computing
- Solar and Space Plasma Dynamics
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- IoT-based Smart Home Systems
- Network Traffic and Congestion Control
- Privacy, Security, and Data Protection
- Robotics and Automated Systems
Sogang University
2021-2024
Korea Advanced Institute of Science and Technology
2004-2023
John Wiley & Sons (Germany)
2017
Korea Institute of Science & Technology Information
2014
SK Communications (South Korea)
2009
Princeton Plasma Physics Laboratory
1998-2008
Princeton University
1994-2007
University of California, Davis
2001
Institute for Atomic and Molecular Physics
2001
Nova Photonics (United States)
2001
Turbulent fluctuations in plasmas with reversed magnetic shear have been investigated on the Tokamak Fusion Test Reactor. Under intense auxiliary heating, these are observed to bifurcate into two states different transport properties. In state better confinement, it has found that level of is very small throughout most region negative shear. By contrast, lower confinement characterized by large bursts which suggest a competition between driving and suppression turbulence. These results...
Simultaneous profile measurements of the toroidal rotation speed and ion temperature during unbalanced neutral beam injection in Tokamak Fusion Test Reactor show that momentum thermal diffusivities are comparable magnitude (${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$\ensuremath{\approxeq}1.5${\mathrm{\ensuremath{\chi}}}_{\mathrm{i}}$) vary similarly with plasma current minor radius. The correlation ${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$...
Neutral-beam--heated plasmas in TFTR show evidence of substantial non-Ohmically driven toroidal current, even for balanced beam momentum input. The observations are inconsistent with calculations including only Ohmic and beam-driven currents, presently can be matched by models the neoclassical bootstrap current.
Off-axis sawteeth are often observed in reversed magnetic shear plasmas when the minimum safety factor $q$ is near or below 2. Fluctuations with $m/n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2/1$ ( $m$ and $n$ poloidal toroidal mode numbers) appear before after crashes. Detailed comparison has been made between measured ${T}_{e}$ profile evaluation during crash a nonlinear numerical magnetohydrodynamics simulation. The good agreement observation simulation indicates that off-axis...
The NSTX operates at low aspect ratio (R/a ∼ 1.3) and high beta (up to 40%), allowing tests of global confinement local transport properties that have been established from higher devices. plasmas are heated by up 7 MW deuterium neutral beams with preferential electron heating as expected for ITER. Confinement scaling studies indicate a strong BT dependence, current dependence is weaker than observed ratio. Dimensionless experiments increase in decreasing collisionality weak degradation...
The relaxation of core transport barriers in TFTR enhanced reversed shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range shear, but increase when local $\mathbf{E}\ifmmode\times\else\texttimes\fi{}\mathbf{B}$ shearing are driven below threshold comparable to fastest linear growth dominant instabilities. Shafranov-shift-induced stabilization alone is not...
A wide variety of fast ion driven instabilities are excited during neutral beam injection (NBI) in the National Spherical Torus Experiment (NSTX) [Nucl. Fusion 40, 557 (2000)] due to large ratio velocity Alfvén velocity, Vfast∕VAlfvén, and high beta. The Vfast∕VAlfvén ITER 39, 2137 (1999)] NSTX is comparable. modes can be divided into three categories: chirping energetic particle (EPM) frequency range 0 120kHz, toroidal eigenmodes (TAE) with a 50kHz 200kHz, compressional global (CAE GAE,...
A tokamak discharge has been formed and maintained through helicity injection, by use of only an external dc low-energy electron beam. The discharge, in a 5-kG toroidal field, evolved to steady-state circular cross section with q(a)=10, q(0)=4, which was for more than 400 L/R periods, the time (60 msec) limited cathode bias supply. density profile reached line-averaged n${\ifmmode\bar\else\textasciimacron\fi{}}_{e}$=2\ifmmode\times\else\texttimes\fi{}${10}^{13}$...
AbstractMicrowave-based diagnostics have found broad application in magnetic fusion plasma and are expected to be widely employed future burning experiments (BPXs). Most of these techniques based directly on the dispersive properties medium that, as shown body paper, results microwave/millimeter wave portion electromagnetic spectrum being particularly well suited for a variety measurements both equilibrium parameters their fluctuations. Electron cyclotron emission provides measurement...
Background/Objectives: Artificial intelligence (AI) integration in colon polyp detection often exhibits high sensitivity but notably low specificity real-world settings, primarily due to reliance on publicly available datasets alone. To address this limitation, we proposed a semi-automatic annotation method using real colonoscopy videos enhance AI model performance and reduce manual labeling labor. Methods: An integrated was trained validated 86,258 training images 17,616 validation images....
Background/Objectives: Artificial intelligence (AI) integration in colon polyp detection often exhibits high sensitivity but notably low specificity real-world settings, primarily due to reliance on publicly available datasets alone. To address this limitation, we proposed a semi-automatic annotation method using real colonoscopy videos enhance AI model performance and reduce manual labeling labor. Methods: An integrated was trained validated 86,258 training images 17,616 validation images....
Significant advances in microwave and millimeter wave technology over the past decade have enabled development of a new generation imaging diagnostics for current envisioned magnetic fusion devices. Prominent among these are electron cyclotron emission imaging, phase interferometers, scattering, reflectometer systems Te ne fluctuations (both turbulent coherent) profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, stellarators. The diagnostic is...
Diagnostic systems for fluctuation measurements in plasmas are, of necessity, evolving from simple one-dimensional (1D) to multidimensional due the complexity magnetohydrodynamics (MHD) and turbulence physics as illustrated by advanced numerical simulations. Using recent significant advancements millimeter wave imaging technology, microwave reflectometry (MIR) electron cyclotron emission (ECEI), simultaneously measuring density temperature fluctuations, have been developed Toroidal...
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
Understanding the behavior of fluctuations in magnetically confined plasmas is essential to advancement turbulence-based transport physics. Though microwave reflectometry has proven be an extremely useful and sensitive tool for measuring small density some circumstances, this technique been shown have limited viability large amplitude, high kθ and/or core measurements. To end, a new instrument based on two-dimensional imaging developed measure over extended plasma region TEXTOR tokamak. This...
In this paper, we propose an Adaptive Hybrid Transmission (AHT) scheme for on-demand mobile IPTV service over broadband wireless access network (i.e. WiMAX, 802.16e). Proposed algorithm utilizes hybrid mechanism which combines multi-channel multicasting and unicast to enhance not only blocking probability but also reduce overall bandwidth consumption of the system has very limited resources compared wired networks. An adaptive resource allocation is proposed, shown achieve minimum...
To study the mechanism of anomalous transport in tokamaks requires use sophisticated diagnostic tools for measurement short-scale turbulent fluctuations. In this article, we describe an attempt at developing a technique capable providing comprehensive description plasma fluctuations with k⊥ρi<1, such as those driven by ion temperature gradient mode tokamaks. The proposed method is based on microwave reflectometry, and stems from series numerical calculations showing that spatial...
Helium ash production and transport have been measured in TFTR deuterium-tritium plasmas using charge-exchange recombination spectroscopy. The helium confinement time, including recycling effects, is 6-10 times the energy time compatible with sustained ignition a reactor. dominated by edge pumping rates rather than core transport. evolution of local thermal density consistent modeling based on previously coefficients classical slowing down alpha particles.
Results obtained from experiments utilizing high-power ion cyclotron range of frequencies (ICRF) heating to stabilize sawtooth oscillations on Tokamak Fusion Test Reactor (TFTR) [Hawryluk et al., Plasma Phys. Controlled 33, 1509 (1991)] are reviewed. The key observations include existence a minimum ICRF power required achieve stabilization, dependence the stabilization threshold relative size deposition profile q=1 volume, and peaking equilibrium pressure current profiles during...
While microwave reflectometry has proven to be a sensitive tool for measuring electron density fluctuations in many circumstances, it also been shown have limited viability core measurements and/or conditions of strong turbulence. To this end, new instrument based on two-dimensional imaging developed measure over an extended plasma region the TEXTOR tokamak. Laboratory characterization performed using corrugated reflecting targets as approximation reflections including turbulent various...
This letter proposes an ultralow power single-inductor multiple-output converter for implantable stimulation system. minimizes the number of switches turning <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and xmlns:xlink="http://www.w3.org/1999/xlink">off</small> to deliver outputs 0.8, 1.8, 20 V, it uses a soft-switching technique all switching nodes. It also operates with self-oscillating controller only when require power. As...
The first experiments utilizing high-power radio waves in the ion cyclotron range of frequencies to heat deuterium–tritium (D–T) plasmas have been completed on Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)]. Results from initial series demonstrated efficient core second harmonic tritium (2ΩT) heating parameter regimes approaching those anticipated for International Thermonuclear Experimental [D. E. Post, Plasma Physics and Controlled Nuclear Research, Proceedings 13th...
Despite suppression of ρi scale turbulent fluctuations, electron thermal transport remains anomalous in NSTX. For this reason, a microwave scattering system will be deployed to directly observe the ω and k spectra ρe fluctuations characterize effect on transport. The employ Gaussian probe beam produced by high power 280 GHz source. A five-channel heterodyne detection measure radial range |kr|=0–20 cm−1. Inboard outboard launch configurations cover most normalized minor radius. Improved...
A two-dimensional electron cyclotron emission imaging (ECEI) diagnostic has been developed in which broad bandwidth radiation is collected by a vertically aligned mixer array and separated frequency band. Using 16 element array, an 8 band receiver attached to each element, time-resolved 16×8 images of temperature profiles fluctuations the TEXTOR plasma are acquired with vertical horizontal channel spacings 11 mm, spot sizes 13 9 respectively. The system wideband tunable from 95 130 GHz,...