A5021555237- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Solar and Space Plasma Dynamics
- Dust and Plasma Wave Phenomena
- Nuclear Materials and Properties
- Laser-induced spectroscopy and plasma
- Metal and Thin Film Mechanics
- High-pressure geophysics and materials
- Electromagnetic Launch and Propulsion Technology
- Engineering Applied Research
- Nuclear Physics and Applications
- Fluid Dynamics and Turbulent Flows
- Semiconductor materials and devices
- Silicon and Solar Cell Technologies
- Aerodynamics and Fluid Dynamics Research
- Atomic and Molecular Physics
- Plasma and Flow Control in Aerodynamics
- Particle Accelerators and Free-Electron Lasers
- Physics of Superconductivity and Magnetism
Plasma Technology (United States)
2015-2024
Massachusetts Institute of Technology
2015-2024
Fusion Academy
2015-2024
Fusion (United States)
2015-2024
Culham Science Centre
2021
Princeton Plasma Physics Laboratory
2009-2021
Culham Centre for Fusion Energy
2021
ITER
2021
Princeton University
2010-2021
Oak Ridge National Laboratory
2009-2021
We develop and test a model, EPED1.6, for the H-mode pedestal height width based upon two fundamental calculable constraints: (1) onset of non-local peeling–ballooning modes at low to intermediate mode number, (2) nearly local kinetic ballooning high number. Calculation these constraints allows unique, predictive determination both width. The present version model is first principles, in that no parameters are fit observations, includes important non-ideal effects. Extensive successful...
An improved energy confinement regime, I-mode, is studied in Alcator C-Mod, a compact high-field divertor tokamak using ion cyclotron range of frequencies (ICRFs) auxiliary heating. I-mode features an edge transport barrier without accompanying particle barrier, leading to several performance benefits. H-mode obtained core impurity accumulation, resulting reduced radiation with high-Z metal wall and ICRF has stationary temperature pedestal localized modes typically absent, while plasma...
The SPARC tokamak is a critical next step towards commercial fusion energy. designed as high-field ( $B_0 = 12.2$ T), compact $R_0 1.85$ m, $a 0.57$ m), superconducting, D-T with the goal of producing gain $Q>2$ from magnetically confined plasma for first time. Currently under design, will continue path Alcator series tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in device. achievable conservative...
Abstract The SPARC tokamak project, currently in engineering design, aims to achieve breakeven and burning plasma conditions a compact device, thanks new developments high-temperature superconductor technology. With magnetic field of 12.2 T on axis 8.7 MA current, is predicted produce 140 MW fusion power with gain Q ≈ 11, providing ample margin respect its mission > 2. All systems are being designed this landmark discharge, thus enabling the study physics operations reactor relevant pave...
Abstract Progress in physics understanding and theoretical model development of plasma transport confinement (TC) the ITPA TC Topical Group since publication ITER Physics Basis (IPB) document (Doyle et al 2007 Nucl. Fusion 47 S18) was summarized focusing on contributions to burning prediction control. This paper provides a general streamlined overview advances that were mainly led by joint experiments activities for last 15 years (see JEX/JA table appendix). starts with scientific strategy...
Plasma profiles and flows in the low- high-field side scrape-off-layer (SOL) regions Alcator C-Mod are found to be remarkably sensitive magnetic separatrix topologies (upper-, lower- double-null) impose topology-dependent flow boundary conditions on confined plasma. Near-sonic plasma along field lines observed SOL, with magnitude direction clearly dependent X-point location. The principal drive mechanism for is a strong ballooning-like poloidal transport asymmetry: parallel arise so as...
Cross-field particle transport in the scrape-off layer (SOL) of Alcator C-Mod [Phys. Plasmas 1, 1511 (1994)] can be characterized by an effective diffusivity (Deff) that increases markedly with distance from separatrix. As a consequence, recycling onto main-chamber walls is large compared to plasma flows into divertor volume. The SOL exhibits two-layer structure: Steep gradients and moderate fluctuation levels are typically found ∼5 mm region near separatrix (near SOL) where parallel...
The pressure at the top of edge transport barrier (or ‘pedestal height’) strongly impacts fusion performance, while large localized modes (ELMs), driven by free energy in pedestal region, can constrain material lifetimes. Accurately predicting height and ELM behavior ITER is an essential element prediction optimization performance. Investigation intermediate wavelength MHD ‘peeling–ballooning’ modes) has led to improved understanding important constraints on mechanism for ELMs. combination...
High-resolution charge-exchange recombination spectroscopic measurements of B5+ ions have enabled the first spatially resolved calculations radial electric field (Er) in Alcator C-Mod pedestal region [E. S. Marmar, Fusion Sci. Technol. 51, 261 (2006)]. These observations offer new challenges for theory and simulation provide important comparisons with other devices. Qualitatively, structure observed on is similar to that tokamaks. However, narrow high-confinement mode (H-mode) Er well widths...
The XGC1 edge gyrokinetic code is used for a high fidelity prediction the width of heat-flux to divertor plates in attached plasma condition. simulation results are validated against empirical scaling $\lambda_q \propto B_P^{-\gamma}$ obtained from present tokamak devices, where $\lambda_q$ mapped outboard midplane and $\gamma_q=1.19$ as defined by T. Eich et al. [Nucl. Fusion 53 (2013) 093031], $B_P$ magnitude poloidal magnetic field at separatrix surface. This predicts \leq 1mm$ when...
The goal of the Lower Hybrid Current Drive (LHCD) system on Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] is to investigate current profile control under plasma conditions relevant future experiments. Experimental observations a LHCD "density limit" for are presented in this paper. Bremsstrahlung emission from relativistic fast electrons core drops suddenly above line averaged densities 1020 m−3 (ω/ωLH∼3–4), well below density limit previously observed other...
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...
A fast edge turbulence suppression event has been simulated in the electrostatic version of gyrokinetic particle-in-cell code XGC1 a realistic diverted tokamak geometry under neutral particle recycling. The results show that sequence turbulent Reynolds stress followed by neoclassical ion orbit-loss driven together conspire to form sustaining radial electric field shear and quench transport just inside last closed magnetic flux surface. main action is located thin layer around ψN≃0.96–0.98,...
One of the most intensely studied aspects magnetic confinement fusion is edge plasma turbulence which critical to reactor performance and operation. Drift-reduced Braginskii two-fluid theory has for decades been widely applied model boundary plasmas with varying success. Towards better understanding in both experiment, we demonstrate that a physics-informed deep learning framework constrained by partial differential equations can accurately learn turbulent fields consistent from observations...
This work characterizes the core transport physics of SPARC early-campaign plasmas using PORTALS-CGYRO framework. Empirical modeling with L-mode confinement indicates an ample window breakeven (Q > 1) without need H-mode operation. Extensive multi-channel (electron energy, ion and electron particle) flux-matched conditions nonlinear CGYRO code for turbulent coupled to macroscopic plasma evolution PORTALS reveals that maximum fusion performance be attained will highly dependent on...
Cross-field particle transport increases sharply with distance into the SOL and plays a dominant role in `main-chamber recycling' regime Alcator C-Mod, which most of plasma efflux recycles on main-chamber walls rather than flows divertor volume. This observation has potentially important implications for reactor: contrary to ideal picture operation, tightly baffled may not offer control neutral density such that charge exchange heat losses sputtering can be reduced. The conditions give rise...
Plasma profiles across the separatrix and scrape-off layer (SOL) in Alcator C-Mod are examined for a range of plasma densities, currents magnetic fields Ohmic L-mode discharges subset conditions H-mode discharges. In all plasmas, electron pressure gradient scale lengths ( ) exhibit minimum value just outside (i.e. near SOL), forming base weak (strong) pedestal (H-mode) plasmas. Over wide discharges, at this location found to track with monotonic function collision frequency, when quantity is...
Experiments in Alcator C-Mod (Enhanced D-alpha) EDA H-modes with extrinsic impurity seeding (N2, Ne, and Ar) have demonstrated a direct correlation between plasma energy confinement edge power flow, achieving values of H98 ≥ 1 for flows only marginally exceeding the scaled access to H-mode these conditions. For lower Z (N2 Ne), plasmas high are obtained radiative fraction 85% or larger reduction peak heat flux at divertor by more than factor 5 compared similar attached The thus achieved meet...
Intrinsic rotation has been observed in $I$-mode plasmas from the $C$-Mod tokamak, and is found to be similar that $H$ mode, both its edge origin scaling with global pressure. Since have $\ensuremath{\nabla}T$, but completely different $\ensuremath{\nabla}n$, it may concluded drive of intrinsic $\ensuremath{\nabla}T$ rather than $\ensuremath{\nabla}P$. Evidence suggests connection between gradients residual stress, a for conversion free energy macroscopic flow calculated.
We report extended studies of the I-mode regime [Whyte et al., Nucl. Fusion 50, 105005 (2010)] obtained in Alcator C-Mod tokamak [Marmar Sci. Technol. 51(3), 3261 (2007)]. This regime, usually accessed with unfavorable ion B × ∇B drift, features an edge thermal transport barrier without a strong particle barrier. Steady I-modes have now been favorable by using specific plasma shapes, as well drift over wider range shapes and parameters. With power thresholds are close to standard scaling for...
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.
Direction reversals of intrinsic toroidal rotation have been observed in diverted Alcator $C$-Mod Ohmic $L$-mode plasmas following electron density ramps. For low discharges, the core is directed cocurrent, and reverses to countercurrent an increase above a certain threshold. Such occur together with decrease fluctuations $2\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}\ensuremath{\le}{k}_{\ensuremath{\theta}}\ensuremath{\le}11\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$ frequencies 70 kHz....
Direction reversals of intrinsic toroidal rotation have been observed in Alcator C-Mod ohmic L-mode plasmas following modest electron density or magnetic field ramps. The reversal process occurs the plasma interior, inside q = 3/2 surface. For low plasmas, is co-current direction, and can reverse to counter-current direction an increase above a certain threshold. Reversals from co- are correlated with sharp decrease fluctuations k R ⩾ 2 cm −1 frequencies 70 kHz. at which reverses increases...
Transport barrier formation and its relation to sheared flows in fluids plasmas are of fundamental interest various natural laboratory observations critical importance achieving an economical energy production a magnetic fusion device. Here we report the first observation edge transport event gyrokinetic simulation carried out realistic tokamak geometry. The results show that turbulent Reynolds stress driven ExB act concert with neoclassical orbit loss quench form just inside last closed...