A5042455402- Magnetic confinement fusion research
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Solar and Space Plasma Dynamics
- Nuclear reactor physics and engineering
- Dust and Plasma Wave Phenomena
- Atomic and Subatomic Physics Research
- Nuclear Materials and Properties
- Fluid Dynamics and Turbulent Flows
- Engineering Applied Research
- Mass Spectrometry Techniques and Applications
- Electromagnetic Launch and Propulsion Technology
- X-ray Spectroscopy and Fluorescence Analysis
- Spacecraft and Cryogenic Technologies
- Advanced Chemical Physics Studies
- Fetal and Pediatric Neurological Disorders
- Metallurgical Processes and Thermodynamics
- Gas Dynamics and Kinetic Theory
Massachusetts Institute of Technology
2014-2024
Plasma Technology (United States)
2015-2024
Fusion (United States)
2015-2024
Fusion Academy
2015-2024
École Polytechnique Fédérale de Lausanne
2023
Colorado State University
1998-2021
IIT@MIT
2001-2017
University of York
2017
Quantum Design (United States)
2015
Princeton Plasma Physics Laboratory
1991-2014
Progress, since the ITER Physics Basis publication (ITER Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding processes that will determine properties of plasma edge and its interaction with material elements is described. Experimental areas where significant progress has taken place are energy transport scrape-off layer (SOL) particular anomalous scaling, particle SOL plays a major role diverted plasmas main-chamber elements, localized mode (ELM) deposition on mechanism for ELM...
A multi-machine database for the H-mode scrape-off layer power fall-off length, λq in JET, DIII-D, ASDEX Upgrade, C-Mod, NSTX and MAST has been assembled under auspices of International Tokamak Physics Activity. Regression inside finds that most important scaling parameter is poloidal magnetic field (or equivalently plasma current), with decreasing linearly increasing Bpol. For conventional aspect ratio tokamaks, regression , yielding λq,ITER ≅ 1 mm baseline inductive burning scenario at Ip...
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...
A tokamak edge phenomenon, dubbed the 'marfe' (for multifaceted asymmetric radiation from edge), is described. This observed in medium- to high-density Alcator C discharges, characterized by greatly increased radiation, density and fluctuations, decreased temperature a relatively small volume at inner major radius of plasma. The marfe appears be confined minor radii greater than or order that limiter. affected region typically above midplane, extending poloidally for about 30° toroidally...
A series of pellet-fueling experiments has been carried out on the Alcator $C$ tokamak. High-speed hydrogen pellets penetrate to within a few centimeters magnetic axis, raise plasma density, and produce peaked density profiles. Energy confinement is observed increase over similar discharges fueled only by gas puffing. In this manner record values electron pressure, Lawson number ($n\ensuremath{\tau}$) have achieved.
The intermittent turbulent transport in the scrape-off-layer (SOL) of Alcator C-Mod [I.H. Hutchinson, R. Boivin, P.T. Bonoli et al., Nucl. Fusion 41, 1391 (2001)] is studied experimentally by imaging with a very high density spatial measurements. two-dimensional structure and dynamics emission from localized gas puff are observed, features (also sometimes called “filaments” or “blobs”) typically seen. characteristics turbulence their relationship to time-averaged SOL profiles discussed...
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...
Regimes of high-confinement mode have been studied in the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)]. with no edge localized modes (ELM-free) compared detail to a new regime, enhanced Dα (EDA). EDA discharges only slightly lower energy confinement than comparable ELM-free ones, but show markedly reduced impurity confinement. Thus do not accumulate impurities and typically fraction radiated power. The gradients seem be relaxed by continuous process rather an...
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...
Abstract Growth of tungsten nano-tendrils (‘fuzz’) has been observed for the first time in divertor region a high-power density tokamak experiment. After 14 consecutive helium L-mode discharges Alcator C-Mod, tip Langmuir probe at outer strike point was fully covered with layer nano-tendrils. The thickness individual (50–100 nm) and depth (600 ± 150 are consistent observations from experiments on linear plasma devices. observation fuzz may have important implications material erosion, dust...
A coordinated effort to measure divertor heat flux characteristics in fully attached, similarly shaped H-mode plasmas on C-Mod, DIII-D, and NSTX was carried out 2010 order construct a predictive scaling relation applicable next step devices including ITER, FNSF, DEMO. Few published laws are available those that have been were obtained under widely varying conditions geometries, leading conflicting predictions for this critically important quantity. This study designed overcome these...
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...
Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into plasma has resulted large improvements deuterium–tritium fusion power production (up to 10.7 MW), Lawson triple product 1021 m−3 s keV), and energy confinement time 330 ms). The maximum current for access high-performance supershots been increased from 1.9 2.7 MA, leading stable operation at stored values greater than 5 MJ. amount on limiter...
Analysis of the experimental data from tokamaks and linear divertor simulators leads to conclusion that plasma recombination is a crucial element detachment. Different mechanisms relevant conditions tokamak scrape-off layer (SOL) are considered. The physics Molecular Activated Recombination (MAR) involving vibrationally excited molecular hydrogen discussed. Although conventional Electron–Ion (EIR) alone can strongly alter parameters, MAR impact be substantial for both SOL simulators....
Radially propagating spatiotemporal fluctuation structures are observed in the scrape-off layer of Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, (1994)] using combination electric probes, a radial array views measuring Dα emission, and two-dimensional imaging emission. For specific magnetic-field configuration probe measured plasma density potential fluctuations along same magnetic-flux tube. Calculations cross-correlation functions intensity with ion saturation current floating...
Transport of trace, non-recycling, injected impurities has been studied on the Alcator C tokamak. Changes impurity confinement times with varying plasma density, current, toroidal field, majority ion species mass, charge and Zeff, major minor radius have delineated. An empirical scaling is developed from these results compared similar transport studies undertaken other tokamak devices. The agreement reasonable. A computer model simulating utilized to compare several models empricial results....
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...
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...
Velocity fields and density fluctuations of edge turbulence are studied in I-mode [F. Ryter et al., Plasma Phys. Controlled Fusion 40, 725 (1998)] plasmas the Alcator C-Mod [I. H. Hutchinson Plasmas 1, 1511 (1994)] tokamak, which characterized by a strong thermal transport barrier while providing little or no to both bulk impurity particles. Although previous work showed clear geodesic-acoustic modes (GAM) on C-Mod, using newly implemented, gas-puff-imaging based time-delay-estimate velocity...
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,...
Gas puff imaging (GPI) is a diagnostic of plasma turbulence which uses neutral gas at the edge to increase local visible light emission for improved space-time resolution fluctuations. This paper reviews diagnostics in magnetic fusion research, with focus on instrumentation, cross-checks, and interpretation issues. The hardware, optics, detectors are described about 10 GPI systems implemented over past ∼15 years. Comparison results other described, many common features observed. Several...
The James Webb Space Telescope (JWST) is a segmented deployable telescope, utilizing 6 degrees of freedom for adjustment the Secondary Mirror (SM) and 7 each its 18 segments in Primary (PM). When deployed, PM SM will be placed their correct optical positions to within few mm, with accordingly large wavefront errors. challenge, therefore, position these elements order deployment errors produce diffraction-limited at λ=2μm, across entire science field. This paper describes suite processes,...
A new “Mirror Langmuir Probe” diagnostic, combined with a double-coil scanning magnetic probe, is used to interrogate Alcator C-Mod's quasi-coherent mode (QCM) unprecedented detail. In ohmic EDA H-modes, the QCM found reside in region of positive radial electric field, width (∼3 mm) that spans open and closed field line regions. Large amplitude, in-phase sinusoidal bursts (∼100 kHz) density, electron temperature, plasma potential are observed, lagging density by ∼16°, producing an outward...
Owing to its high magnetic field, power, and compact size, the SPARC experiment will operate with divertor conditions at or above those expected in reactor-class tokamaks. Power exhaust this scale remains one of key challenges for practical fusion energy. Based on empirical scalings, peak unmitigated parallel heat flux is projected be greater than 10 GW m −2 . This nearly an order magnitude higher has been demonstrated date. Furthermore, Edge-Localized Mode (ELM) energy fluence projections...