A5007320715- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-induced spectroscopy and plasma
- Dust and Plasma Wave Phenomena
- High-pressure geophysics and materials
- Semiconductor materials and devices
- Solar and Space Plasma Dynamics
- Additive Manufacturing Materials and Processes
- Additive Manufacturing and 3D Printing Technologies
- Atomic and Molecular Physics
- Physics of Superconductivity and Magnetism
- Geophysics and Sensor Technology
- Aeroelasticity and Vibration Control
- Water Systems and Optimization
- Aerospace Engineering and Energy Systems
- Spectroscopy Techniques in Biomedical and Chemical Research
- Metallurgical Processes and Thermodynamics
- GNSS positioning and interference
- Muon and positron interactions and applications
- Gear and Bearing Dynamics Analysis
Beijing University of Technology
2024-2025
Jilin University
2023
Xi'an University of Technology
2021-2023
Massachusetts Institute of Technology
2013-2022
Plasma Technology (United States)
2012-2016
Fusion Academy
2012-2016
Fusion (United States)
2012-2016
Princeton Plasma Physics Laboratory
2015
The University of Texas at Austin
2015
Xidian University
2014
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...
This research describes advancements in the spectral analysis and error propagation techniques associated with x-ray imaging crystal spectroscopy (XICS) that have enabled this diagnostic to be used accurately constrain particle, momentum, heat transport studies a tokamak for first time. Doppler tomography been extended include of statistical uncertainty due photon noise, effect non-uniform instrumental broadening as well flux surface variations impurity density. These methods deployed suite...
Several seemingly unrelated effects in Alcator C-Mod ohmic L-mode plasmas are shown to be closely connected: non-local heat transport, core toroidal rotation reversals, energy confinement saturation and up/down impurity density asymmetries. These phenomena all abruptly transform at a critical value of the collisionality. At low densities linear regime, with collisionality ?*???0.35 (evaluated inside q?=?3/2 surface), transport exhibits behaviour, is directed co-current, edge profiles...
Ohmic energy confinement saturation is found to be closely related core toroidal rotation reversals in Alcator C-Mod tokamak plasmas. Rotation occur at a critical density, depending on the plasma current and magnetic field, which coincides with density separating linear regime from saturated regime. The directed co-current low abruptly changes direction counter-current when saturates as increased. Since there bifurcation of this reversal very sensitive indicator determination change. results...
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...
Core impurity transport has been investigated for a variety of confinement regimes in Alcator C-Mod plasmas from x-ray emission following injection medium and high Z materials. In ohmic L-mode discharges, is anomalous (Deff ≫ Dnc) changes very little across the LOC/SOC boundary. ion cyclotron range frequencies (ICRF) heated plasmas, core time decreases with increasing ICRF input power (and subsequent electron temperature) increases plasma current. Nearly identical characteristics are...
Abstract Electromechanical actuators play a crucial role in various fields of engineering and physics, including aerospace automotive industries. The dynamics have major effect on the aeroelastic fins, especially flutter boundary. However, determining dynamic properties involves complicated interaction several linear nonlinear components. In this study, high-fidelity model is proposed to effectively address complexities an electromechanical fin-actuator. comprehensive incorporates essential...
New observations of the formation and dynamics long-lived impurity-induced helical ``snake'' modes in tokamak plasmas have recently been carried out on Alcator C-Mod. The snakes form as an asymmetry impurity ion density that undergoes a seamless transition from small helically displaced to large crescent-shaped structure inside $q<1$, with regularly sawtoothing core. show conditions for persistence snake cannot be explained by plasma pressure alone. Instead, many features arise naturally...
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...
Application of lower hybrid (LH) current drive in tokamak plasmas can induce both co- and countercurrent directed changes toroidal rotation, depending on the core q profile. For discharges with q0<1, rotation increments direction are observed. If LH-driven is sufficient to suppress sawteeth increase q0 above unity, change cocurrent direction. This sign increment consistent a residual stress (the divergence which constitutes an intrinsic torque that drives flow) through its dependence...
Application of lower hybrid range frequencies (LHRF) waves can induce both co- and counter-current directed changes in toroidal rotation Alcator C-Mod plasmas, depending on the target plasma current, electron density, confinement regime magnetic shear. For ohmic L-mode discharges with good core LH wave absorption, significant current drive at a fixed power near 0.8 MW, interior (r/a < 0.5) increments (on time scale order relaxation time) direction if ne(1020 m−3) > q95/11.5, co-current...
X-ray spectra of n = 2 to 1 transitions in hydrogen-like Ca19 +, helium-like Ca18 + and nearby satellites have been obtained from Alcator C-Mod tokamak plasmas using a spatially imaging high resolution x-ray spectrometer system. For the intensity ratio Lyα2 (1s 1S1/2–2p 2P1/2) Lyα1 2P3/2) was found be ∼0.531 ± 0.005 over range plasma parameters, which is somewhat greater than statistical weights upper levels, 1/2. This difference mainly due interaction with 2S1/2 fine structure sub-level....
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...
Long-lived (1, 1) 'snake' modes were discovered nearly three decades ago, but basic questions regarding their formation, stability, and superb particle confinement—shown by surviving tens to hundreds of sawtooth cycles—have remained unanswered. High-resolution spectroscopic imaging diagnostics permit studies heavy-impurity-ion snakes with unprecedented temporal spatial resolution, making it possible positively identify the SXR signals specific ion charge states infer, for first time,...
The physical mechanisms that cause tokamak plasmas to rotate toroidally without external momentum input are of considerable interest the plasma physics community. This paper documents a substantial change in both magnitude core-rotation frequency, −1 < ω(r/a = 0) +10 kHz, and sign rotation shear at mid-radius, u' −R2 dω/dr/vth,i, which varies range −0.6 +0.8 response very small changes electron density. In 0.8 MA, 5.4 T Alcator C-Mod L-mode using 1.2 MW on-axis ion-cyclotron resonance...
Intrinsic torque, which can be generated by turbulent stresses, induce toroidal rotation in a tokamak plasma at rest without direct momentum injection. Reversals intrinsic torque have been inferred from the observation of velocity changes recent lower hybrid current drive (LHCD) experiments. This work focuses on understanding cause LHCD-induced reversal using gyrokinetic simulations and theoretical analyses. A new mechanism for linked to magnetic shear ( ŝ) effects turbulence spectrum is...
Changes in rotation have been observed LHCD experiments. From these observations, reversals intrinsic torque inferred. This paper identifies the mechanism for reversal linked to magnetic shear (). Gyrokinetic simulations demonstrate that as compared normal case, reverses, . Analysis shows occurs due dominance of symmetry breaking residual stress synergy toroidal coupling and intensity gradient. is a consequence ballooning structure at weak simulation gives trapped electron modes (TEM) ion...
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...
This paper presents an overview of recent highlights from research on Alcator C-Mod. Significant progress has been made across all areas over the last two years, with particular emphasis divertor physics and power handling, plasma–material interaction studies, edge localized mode-suppressed pedestal dynamics, core transport turbulence, RF heating current drive utilizing ion cyclotron lower hybrid tools. Specific results relevance to ITER include: inner wall SOL studies that have led,...
X-ray spectra of H-and He-like ions (and satellites) from argon, calcium and chlorine have been obtained Alcator C-Mod tokamak plasmas using a high resolution x-ray spectrometer system.For H-like charge states, the Ly α doublet intensity ratio is found to be slightly greater than 1/2 due interaction with 2 S fine structure sub-level.Neighbouring satellites spectator electrons occupying n = through 7 modelled.The scalings electron density temperature are shown in good agreement...
Abstract Changes in the core toroidal rotation profiles following injection of lower hybrid (LH) waves have been documented Alcator C-Mod plasmas. Shot by shot scans LH input power performed at fixed magnetic field and electron density for several plasma currents. For sawtoothing target plasmas, if is low enough that central safety factor q 0 remains below 1, change counter-current direction, consistent sign, magnitude scaling with direct momentum from waves. If level high there are...
New experimental observations are reported on the structure and dynamics of short-lived periodic (1, 1) “fishbone”-like oscillations that appear during radio frequency heating current-drive experiments in tokamak plasmas. For first time, measurements can directly relate changes high energy electrons to mode onset, saturation, damping. In relatively collisionality Alcator C-Mod with lower hybrid current drive, instability appears be destabilized by non-resonant suprathermal electron...
X-ray imaging crystal spectrometers with high spectral and spatial resolution are currently being used on magnetically confined fusion devices to infer the time history profiles of ion electron temperatures as well plasma flow velocities. The absolute measurement velocities is important for optimizing various discharge scenarios evaluating radial electric field in tokamak stellarator plasmas. Recent studies indicate that temperature must be kept constant within a fraction degree avoid...