A5028413552- Magnetic confinement fusion research
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Gyrotron and Vacuum Electronics Research
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Advanced X-ray Imaging Techniques
- Semiconductor materials and devices
- Nuclear Physics and Applications
- Silicon and Solar Cell Technologies
- Laser-induced spectroscopy and plasma
- Laser Design and Applications
- Terahertz technology and applications
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Fault Detection and Control Systems
- Metallurgical Processes and Thermodynamics
- Laser-Matter Interactions and Applications
- Atomic and Molecular Physics
- Electrostatic Discharge in Electronics
- Electron and X-Ray Spectroscopy Techniques
- Metal and Thin Film Mechanics
Korea Advanced Institute of Science and Technology
2021-2024
University of California, Los Angeles
2005-2021
Korea Institute of Fusion Energy
2020
Massachusetts Institute of Technology
2011-2019
Fusion Academy
2012-2019
Fusion (United States)
2012-2019
Lam Research (United States)
2019
The University of Texas at Austin
2019
Lawrence Livermore National Laboratory
2019
General Atomics (United States)
2019
This paper introduces a new approach to measure the muon magnetic moment anomaly |$a_{\mu} = (g-2)/2$| and electric dipole (EDM) |$d_{\mu}$| at J-PARC facility. The goal of our experiment is |$a_{\mu}$| using an independent method with factor 10 lower momentum, 20 smaller diameter storage-ring solenoid compared previous ongoing |$g-2$| experiments unprecedented quality storage field. Additional significant differences from present experimental include 1000 transverse emittance beam...
Plasma discharges with a negative triangularity (δ=−0.4) shape have been created in the DIII-D tokamak significant normalized beta (βN=2.7) and confinement characteristic of high mode (H98y2=1.2) despite absence an edge pressure pedestal no localized modes (ELMs). These inner-wall-limited plasmas similar global performance as positive (δ=+0.4) ELMing H-mode discharge same plasma current, elongation cross sectional area. For cases both dominant electron cyclotron heating Te/Ti>1 neutral beam...
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...
Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within auxiliary power available for these experiments, plasmas exhibit near-zero degradation while sustaining βN = 2.7 and H98,y2 1.2 several energy confinement times. Detailed comparison matched discharges at positive indicates that Trapped Electron Modes are weakened...
We present the first localized measurements of long and intermediate wavelength turbulent density fluctuations (ñ) electron temperature (T̃e) modified by m/n=2/1 Neoclassical Tearing Mode (NTM) islands (m n are poloidal toroidal mode numbers, respectively). These wavelengths correspond to expected Ion Temperature Gradient Trapped Electron scales, respectively. Two regimes have been observed when tracking ñ during NTM evolution: (1) small characterized a steep Te radial profile turbulence...
Abstract Further investigation of fast ion effects on turbulence and transport in the regulated enhancement (FIRE) mode discharge (Han et al 2022 Nature 609 269–275) was performed this work as a continuation previous study (Kim 2023 Nucl. Fusion 63 124001) that showed dominant suppression mechanism by ions is dilution effect FIRE discharge. The current includes (i) impact relevant observed simulation thermal energy flux, (ii) compared to other species, (iii) electron-scale turbulence. First,...
Abstract The edge region of the recently discovered fast ion-regulated enhancement mode (FIRE mode) (Han and Park et al 2022 Nature 609 269–275), which primarily operates in unfavorable ion <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">∇</mml:mi> <mml:mi>B</mml:mi> </mml:mrow> </mml:math> drift configuration, is investigated detail for first time. An temperature pedestal identified, while electron density profile remains...
Multi-channel transport experiments have been conducted in auxiliary heated (Ion Cyclotron Range of Frequencies) L-mode plasmas at Alcator C-Mod [Marmar and Group, Fusion Sci. Technol. 51(3), 3261 (2007)]. These provide good diagnostic coverage for measurements kinetic profiles, impurity transport, turbulence (electron temperature density fluctuations). In the experiments, a steady sawtoothing plasma with 1.2 MW on-axis RF heating is established scanned by 20%. Measured rotation profiles...
New results on the I-mode regime of operation Alcator C-Mod tokamak are reported. This ELM-free features high energy confinement and a steep temperature pedestal, while particle remains at L-mode levels, giving stationary density avoiding impurity accumulation. has now been obtained over nearly all magnetic fields currents possible in this field (Ip 0.55–1.7 MA, BT 2.8–8 T) using configuration with B × ∇B drift away from X-point. Results 8 T confirm that L–I power threshold varies only...
New measurements of electron temperature fluctuations associated with the weakly coherent mode (WCM) during improved mode, or I-mode plasmas (Whyte et al 2010 Nucl. Fusion . 50 105005 ) at Alcator C-Mod (Marmar 2007 Fusion. Sci. Technol. 51 3261) are presented in this paper. The made a 32-channel, high-resolution profile cyclotron emission radiometer. WCM localized to 1 cm region inside last closed flux surface. fluctuation level is measured several different discharges and range , which an...
The first measurements of long wavelength (kyρs < 0.3) electron temperature fluctuations in Alcator C-Mod made with a new correlation cyclotron emission diagnostic support long-standing hypothesis regarding the confinement transition from linear ohmic (LOC) to saturated (SOC). Electron decrease significantly (∼40%) crossing LOC SOC, consistent change trapped mode (TEM) turbulence domination ion gradient (ITG) as density is increased. Linear stability analysis performed GYRO code (Candy and...
Abstract This letter provides a new physical insight into the fast ion effects on turbulence in plasmas having high fraction and peaked density profile. We elucidate stabilization mechanisms by ions that result internal transport barrier formation regulated enhancement mode plasma. Both linear nonlinear gyrokinetic simulations show dominant suppression are dilution effects. In particular, we find can be sufficiently suppressed solely an inverted main gradient due to ions, for first time. New...
Abstract The Korean Superconducting Tokamak Advanced Research has been focused on exploring the key physics and engineering issues for future fusion reactors by demonstrating long pulse operation of high beta steady-state discharge. scenarios are being developed with goal operation, significant progress made in ℓ i , hybrid β N 3. In new scenario called fast ion regulated enhanced (FIRE), ions play an essential role confinement enhancement. GK simulations show a reduction thermal energy flux...
Energy gain of trapped electrons in excess 20 MeV has been demonstrated an inverse-free-electron-laser (IFEL) accelerator experiment. A 14.5 electron beam is copropagated with a 400 GW CO2 laser 50 cm long undulator strongly tapered period and field amplitude. The Rayleigh range the laser, approximately 1.8 cm, much shorter than length yielding diffraction-dominated interaction. Experimental results on dependence acceleration injection energy, focus position, power are discussed....
A new eight-channel correlation electron cyclotron emission diagnostic has recently been installed on the DIII-D tokamak to study both turbulent and coherent temperature fluctuations under various plasma conditions locations. This unique system is designed cover a broad range of operation space (1.6-2.1 T, detection frequency: 72-108 GHz) via four remotely selected local oscillators (80, 88, 96, 104 GHz). Eight radial locations are measured simultaneously in single discharge covering as much...
The first energetic particle experiments in negative triangularity tokamak plasmas have been carried out on DIII-D. Alfvén eigenmode (AE) activity and associated fast ion transport comparable to that positive is observed during the current ramp portion of all with early beam heating indicating does not confer a special advantage respect AE induced transport. In these discharges, range mode driven by sub-Alfvénic () 80 kV neutral beams found including beta acoustic eigenmodes, reversed shear...
We extend the bounce-averaged kinetic (BK) electron model to be applicable in general tokamak magnetic geometries and implement it on global δf particle-in-cell gyrokinetic code gKPSP. perform a benchmark study of updated BK against flux-tube codes, CGYRO GENE. From comparisons among simulations based local parameters KSTAR L-mode plasma, we confirm reasonable agreement linear results from different codes. In nonlinear gKPSP simulation with narrow plasma gradient region whose width...
Non-local heat transport experiments were performed in Alcator C-Mod ohmic L-mode plasmas by inducing edge cooling with laser blow-off impurity (CaF2) injection. The non-local effect, a of the electron temperature rapid rise central temperature, which contradicts assumption ?local? transport, was observed low collisionality linear confinement (LOC) regime plasmas. Transport analysis shows this phenomenon can be explained either fast drop core diffusivity, or sudden appearance pinch. In high...
New validation of global, nonlinear, ion-scale gyrokinetic simulations (GYRO) is carried out for L- and I-mode plasmas on Alcator C-Mod, utilizing heat fluxes, profile stiffness, temperature fluctuations. Previous work at C-Mod found that ITG/TEM-scale GYRO can match both electron ion fluxes within error bars in [White PoP 2015], suggesting multi-scale (cross-scale coupling) effects [Howard 2016] may be less important than L-mode. results presented here, however, show are able to the...
The first observation of increased electron temperature turbulence during edge localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) is presented. These are long wavelength fluctuations (kθρs ≤ 0.2, where kθ = poloidal wavenumber and ρs ion sound gyroradius) observed H-mode plasmas on the DIII-D. This increase occurs only after ELMs suppressed not initial RMP application. T̃e/Te increases (&gt;60%) coincident with changes in normalized density gradients region from...
A correlation electron cyclotron emission (CECE) diagnostic has been installed in Alcator C-Mod. In order to measure temperature fluctuations, this uses a spectral decorrelation technique. Constraints obtained with nonlinear gyrokinetic simulations guided the design of optical system and receiver. The CECE is designed fluctuations which have k(θ) ≤ 4.8 cm(-1) (k(θ)ρ(s) < 0.5) using well-focused beam pattern. Because dedicated turbulence diagnostic, also flexible, allows for various...
For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. is a high confinement regime, featuring energy similar to H-mode, but without enhanced particle impurity [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As consequence separation between heat transport, exhibits several favorable characteristics H-mode. The code GYRO [J. Candy R. E. Waltz, J Comput. Phys. 186, 545 (2003)] used explore effects E × B shear profile stiffness...
Recent research on the Alcator C-Mod tokamak has focused a range of scientific issues with particular emphasis ITER needs and detailed comparisons between experimental measurements predictive models. Research ICRF (ion cyclotron frequencies) heating emphasized origins mitigation metallic impurities while work lower hybrid current drive experiments have linear nonlinear wave interactions that limit efficiency at high densities in regimes low single pass absorption. Experiments core turbulence...