A5056032238- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Semiconductor materials and devices
- Electromagnetic Launch and Propulsion Technology
- Fluid Dynamics and Turbulent Flows
- Nuclear Physics and Applications
- High-pressure geophysics and materials
- Silicon and Solar Cell Technologies
- Electrostatic Discharge in Electronics
- Advancements in Semiconductor Devices and Circuit Design
- Atomic and Subatomic Physics Research
- Meteorological Phenomena and Simulations
- Electron and X-Ray Spectroscopy Techniques
- Physics of Superconductivity and Magnetism
- Advanced Data Storage Technologies
- Metal and Thin Film Mechanics
- Laser-induced spectroscopy and plasma
- Gamma-ray bursts and supernovae
Fusion (United States)
2016-2025
Plasma Technology (United States)
2016-2025
Massachusetts Institute of Technology
2016-2025
Fusion Academy
2016-2025
Western Washington University
2024
Auburn University
2024
University of California, San Diego
2010-2020
General Atomics (United States)
2010-2020
University of Wisconsin–Madison
2010-2020
Princeton Plasma Physics Laboratory
2008-2020
Abstract The transport of heat in laboratory and astrophysical plasmas is dominated by the complex nonlinear dynamics plasma turbulence. In magnetically confined used for fusion energy research, turbulence responsible cross-field that limits performance tokamak reactors. We report a set novel gyrokinetic simulations capture ion electron-scale simultaneously, revealing cross-scale transfer zonal flow modification give rise to losses. Multi-scale are required match experimental electron fluxes...
Improved profile
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...
The deployment of multiple high-resolution, spatially localized fluctuation diagnostics on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] opens door to a new level core turbulence model validation. Toward this end, implementation synthetic that physical beam emission spectroscopy and correlation electron cyclotron is presented. Initial results from their applications local gyrokinetic simulations two locations in L-mode discharge performed with GYRO code Candy R. E. Waltz, J....
For the first time, profiles (0.3<ρ<0.9) of electron temperature and density fluctuations in a tokamak have been measured simultaneously results compared to nonlinear gyrokinetic simulations. Electron neutral beam-heated, sawtooth-free low confinement mode (L-mode) plasmas DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] are found be similar frequency normalized amplitude, with amplitude increasing radius. The radial profile two fluctuation fields allows for new rigorous...
A series of carefully designed experiments on DIII-D have taken advantage a broad set turbulence and profile diagnostics to rigorously test gyrokinetic simulations. In this paper the goals, tools performed in these validation studies are reviewed specific examples presented. It is found that predictions transport fluctuation levels mid-core region (0.4 < ρ 0.75) better agreement with experiment than those outer (ρ ⩾ where edge coupling effects may become increasingly important multiscale...
The MIT Plasma Science and Fusion Center collaborators are proposing a high-performance Advanced Divertor RF tokamak eXperiment (ADX)-a specifically designed to address critical gaps in the world fusion research programme on pathway next-step devices: nuclear science facility (FNSF), pilot plant (FPP) and/or demonstration power (DEMO). This high-field (>= 6.5 T, 1.5 MA), high density (P/S similar MW m(-2)) will test innovative divertor ideas, including an 'X-point target divertor' concept,...
With fusion device performance hinging on the edge pedestal pressure, it is imperative to experimentally understand physical mechanism dictating characteristics and validate improve predictive models. This Letter reports direct evidence of density magnetic fluctuations showing stiff onset an instability leading saturation Alcator C-Mod tokamak. Edge stability analyses indicate that unstable both ballooning mode kinetic in agreement with observations.
Robust validation of predictive turbulent transport models requires quantitative comparisons to experimental measurements at multiple levels, over a range physically relevant conditions. Toward this end, series carefully designed experiments has been performed on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] obtain comprehensive multifield, multipoint, multiwavenumber fluctuation and their scalings with key dimensionless parameters. The results two representative studies are...
Abstract This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport no localized modes (ELMs). The regime has been demonstrated on Alcator C-Mod, ASDEX Upgrade DIII-D tokamaks, over a wide range device parameters pedestal conditions. Dimensionless at show overlap across devices extend to low collisionality. When they are matched, temperature profiles also similar. Pedestals stable...
To better understand the role of cross-scale coupling in experimental conditions, a series multi-scale gyrokinetic simulations were performed on Alcator C-Mod, L-mode plasmas. These simulations, using all inputs and realistic ion to electron mass ratio ((mi/me)1∕2 = 60.0), simultaneously capture turbulence at (kθρs∼O(1.0)) electron-scales (kθρe∼O(1.0)). Direct comparison with heat fluxes profile stiffness indicates that Electron Temperature Gradient (ETG) streamers strong likely exist both...
Previous nonlinear gyrokinetic simulations of specific DIII-D L-mode cases have been found to significantly underpredict the ion heat transport and associated density temperature fluctuation levels by up almost one order magnitude in outer-core domain, i.e., roughly last third minor radius. Since then, this so-called shortfall issue has subject various speculations on possible reasons furthermore motivation for a number dedicated comparisons plasmas comparable machines. However, only rather...
Experimental conditions obtained on the DIII-D tokamak in ITER Similar Shape (ISS) have been compared extensively with nonlinear gyrokinetic simulation using CGYRO code [Candy et al., J. Comput. Phys. 324, 73–93 (2016)] comparisons spanning ion and electron heat fluxes, impurity particle transport, turbulent fluctuation levels characteristics. Bayesian optimization techniques [Rodriguez-Fernandez Nucl. Fusion 62(7), 076036 (2022)], combined gyrokinetics, used to obtain simultaneously Qi, Qe,...
This paper presents new measurements of the cross-phase angle, αneTe, between long-wavelength (kθρs&lt;0.5) density, ñe, and electron temperature, T̃e, fluctuations in core DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] tokamak plasmas. The coherency angle ñe T̃e are measured using coupled reflectometer correlation cyclotron emission diagnostics that view same plasma volume. In addition to experimental results, two sets local, nonlinear gyrokinetic turbulence simulations performed...
The injected power required to induce a transition from L-mode H-mode plasmas is found depend strongly on the neutral beam torque and consequent plasma toroidal rotation. Edge turbulence flows, measured near outboard midplane of (0.85 < r / 1.0) DIII-D with high-sensitivity 2D emission spectroscopy (BES) system, likewise vary rotation suggest causative connection. L–H threshold in ion ∇ B drift directed away X-point decreases 4–6 MW co-current injection, 2–3 zero net <2...
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...
Abstract Nonlinear gyrokinetic simulations of impurity transport are compared to experimental for the first time. The GYRO code (Candy and Waltz 2003 J. Comput. Phys. 186 545) was used perform global, nonlinear a standard Alcator C-Mod, L-mode discharge. laser blow-off technique combined with soft x-ray measurements single charge state calcium provide time-evolving profiles this non-intrinsic, non-recycling over radial range 0.0 ⩽ r / 0.6. Experimental coefficient their uncertainties were...
Joint experiment/theory/modelling research has led to increased confidence in predictions of the pedestal height ITER. This work was performed as part a US Department Energy Research Target FY11 identify physics processes that control H-mode structure. The study included experiments on C-Mod, DIII-D and NSTX well interpretation experimental data with theory-based modelling codes. provides ability models for peeling–ballooning stability, bootstrap current, width scaling make correct...
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...
For the first time, nonlinear gyrokinetic simulations spanning both ion and electron spatio-temporal scales have been performed with realistic mass ratio ((mD∕me)1∕2 = 60.0), geometry, all experimental inputs, demonstrating coexistence synergy of (kθρs∼O(1.0)) electron-scale (kθρe∼O(1.0)) turbulence in core a tokamak plasma. All multi-scale utilized GYRO code [J. Candy R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] to study coupling (r/a 0.6) an Alcator C-Mod L-mode discharge shown...
Abstract This work presents the PORTALS framework (Rodriguez-Fernandez et al 2022 Nucl. Fusion 62 076036), which leverages surrogate modeling and optimization techniques to enable prediction of core plasma profiles performance with nonlinear gyrokinetic simulations at significantly reduced cost, no loss accuracy. The efficiency is benchmarked against standard methods, its full potential demonstrated on a unique, simultaneous 5-channel (electron temperature, ion electron density, impurity...
The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising diamagnetic effects, introduce strong dependence the radial flux co-current toroidal angular collisionality: As plasma goes nearly collisionless to weakly collisional, reverses direction radially inward outward. This indicates collisionality-dependent transition peaked hollow rotation profiles, consistent with experimental...
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...
Electron profile stiffness was studied in DIII-D L-mode discharges by systematically varying the heat flux a narrow region with electron cyclotron heating and measuring local change produced ∇Te. found to slowly increase toroidal rotation velocity. A critical inverse temperature gradient scale length 1/LC ∼ 3 m−1 identified at ρ=0.6 be independent of rotation. Both pulse diffusivity power balance diffusivity, latter determined integrating measured dependence on –∇Te, were fit reasonably well...