A5070244572- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Particle accelerators and beam dynamics
- Nuclear Physics and Applications
- Anomaly Detection Techniques and Applications
- Nuclear reactor physics and engineering
- Dust and Plasma Wave Phenomena
- Atomic and Subatomic Physics Research
- Solar and Space Plasma Dynamics
- Advanced Data Storage Technologies
- Laser-induced spectroscopy and plasma
- Medical Imaging Techniques and Applications
- Nuclear Materials and Properties
- High-pressure geophysics and materials
- Physics of Superconductivity and Magnetism
- Nuclear Engineering Thermal-Hydraulics
- Atomic and Molecular Physics
- Combustion and Detonation Processes
- Network Security and Intrusion Detection
- Spacecraft and Cryogenic Technologies
- Engineering Applied Research
Plasma Technology (United States)
2016-2025
Fusion Academy
2016-2025
Fusion (United States)
2016-2025
Massachusetts Institute of Technology
2015-2024
Office of Science
2016
Princeton Plasma Physics Laboratory
1990-2015
The University of Texas at Austin
2015
IIT@MIT
2013
General Atomics (United States)
1990-2008
University of California, San Diego
2008
Progress in the area of MHD stability and disruptions, since publication 1999 ITER Physics Basis document (1999 Nucl. Fusion 39 2137–2664), is reviewed. Recent theoretical experimental research has made important advances both understanding control tokamak plasmas. Sawteeth are anticipated baseline ELMy H-mode scenario, but tools exist to avoid or them through localized current drive fast ion generation. Active other instabilities will most likely be also required ITER. Extrapolation from...
Early operation of the Alcator-C-MOD tokamak [I.H. Hutchinson, Proceedings IEEE 13th Symposium on Fusion Engineering, Knoxville, TN, edited by M. Lubell, Nestor, and S. Vaughan (Institute Electrical Electronic Engineers, New York, 1990), Vol. 1, p. 13] is surveyed. Reliable operation, with plasma current up to 1 MA, has been obtained, despite massive conducting superstructure associated error fields. However, vertical disruptions are not slowed long vessel time constant. With pellet fueling,...
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...
The SPARC Toroidal Field Model Coil (TFMC) Program was a three-year effort between 2018 and 2021 that developed novel Rare Earth Barium Copper Oxide (REBCO) superconductor technologies then successfully utilized these to design, build, test first-in-class, high-field (∼20 T), representative-scale (∼3 m) superconducting toroidal field (TF) coil. program executed jointly by the MIT Plasma Science Fusion Center (PSFC) Commonwealth Systems (CFS) as technology enabler of pathway fusion energy,...
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.
A series of experiments, examining the confinement properties ion cyclotron range frequencies (ICRF) heated H mode plasmas, has been carried out on Alcator C-Mod tokamak. is a compact tokamak that operates at high particle, power and current densities toroidal fields up to 8 T. Under these conditions plasma essentially thermal with very little contribution stored energy from energetic ions (typically no more than 5%) Ti~Te. Most data were taken machine in single null `closed' divertor...
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 rapid collapse of a sawtooth oscillation in the JET tokamak has been observed detail on fast time scale. Tomographic reconstruction data from two x-ray cameras and electron-cyclotron-emission temperature profiles show that during central hot region is rapidly (in approximately 100 \ensuremath{\mu}s) displaced off axis with an $m=1$ component then redistributed around surface constant minor radius. theoretical implications measurements are discussed.
Measurements of soft X-ray emission from the JET plasma have been analysed with tomographic reconstruction methods. Because there are two detector arrays, two-dimensional images emissivity obtained without having to resort rotation models. Several algorithms employed in order get as much detail possible while keeping any guiding assumptions a minimum. The data so far used principally study MHD instabilities, and illustrative examples sawtooth crash disruptions described.
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 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 disruption prediction algorithm, called using random forests (DPRF), has run in real-time the DIII-D plasma control system (PCS) for more than 900 discharges. DPRF naturally provides a probability mapping associated with its predictions, i.e. disruptivity signal, now incorporated PCS. This paper discusses accomplishments terms of shot-by-shot performances, by simulating alarms on each discharge as PCS framework. Depending optimised performance metric chosen to evaluate DPRF, we find that...
Using data-driven methodology, we exploit the time series of relevant plasma parameters for a large set disrupted and non-disrupted discharges to develop classification algorithm detecting disruptive phases in shots that eventually disrupt. Comparing same methodology on different devices is crucial order have information portability developed possible extrapolation ITER. Therefore, use data from two very tokamaks, DIII-D Alcator C-Mod. We focus subset disruption predictors, most which are...
This paper reports on disruption prediction using a shallow machine learning method known as random forest, trained large databases containing only plasma parameters that are available in real-time Alcator C-Mod, DIII-D, and EAST. The database for each tokamak contains sampled ∼106 times throughout ∼104 discharges (disruptive non-disruptive) over the last four years of operation. It is found number (e.g. , ) exhibit changes aggregate approached one or more these tokamaks. However, machine,...
The SPARC Toroidal Field Model Coil (TFMC) experimental tests are described. include detailed comparisons to a hierarchy of electromagnetic and structural models the coil. confirmed ability no-insulation no-twist (NINT) configuration provide highly stable DC operations with peak magnetic field in excess 20 tesla at REBCO tape stacks. advantages modular TFMC approach were validated including test probe response coil stages; strategy that will be applied large-scale production for SPARC....
Nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence, within an internal particle transport barrier, are performed and compared with experimental data. The results provide a mechanism for barrier control on-axis radio frequency heating, as demonstrated in Alcator C-Mod experiments [S. J. Wukitch et al., Phys. Plasmas 9, 2149 (2002)]. Off-axis heating produces energy after the transition to enhanced Dα high confinement mode. foot reaches half-radius, peak density 2.5...
A set of external coils (A-coils) capable producing nonaxisymmetric, predominantly n=1, fields with different toroidal phase and a range poloidal mode m spectra has been used to determine the threshold amplitude for locking over plasma parameters in Alcator C-Mod [I. H. Hutchinson, R. Boivin, F. Bombarda, P. Bonoli, S. Fairfax, C. Fiore, J. Goetz, Golovato, Granetz, M. Greenwald et al., Phys. Plasmas 1, 1511 (1994)]. The perturbations parametric scalings, expressed terms (B21∕BT), are...
The ITER Threshold Database, which at present comprises data from nine divertor tokamaks, is described. main results are presented and discussed. properties dependences of the power threshold in individual devices reviewed. In particular, analysis shows a rather general linear dependence on magnetic field, but non-monotonic density that varies device to device. Investigation combined database suggests P thres approximately=0.3n e B T 2.5 reasonable agreement with data. This expression yields...
Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas. The time evolution of core impurity toroidal rotation velocity profiles measured with a tangentially viewing crystal x-ray spectrometer array. Following the L-mode to EDA (enhanced Dα) H-mode transition both Ohmic and ion cyclotron range frequencies heated discharges, ensuing co-current velocity, which is generated absence any external source, propagate from edge plasma timescale order energy confinement time,...
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...
MHD simulations of rapid shutdown scenarios by massive particle injection in DIII-D, Alcator C-Mod and ITER are performed order to study runaway electron (RE) transport during mitigated disruptions. The include a RE confinement model using drift-orbit calculations for test particles. A comparison limited diverted plasma shapes is studied DIII-D simulations, improved the shape found due both spatial localization reduced toroidal spectrum nonlinear activity. compare which impurity (Ar)...
Recent results from an ITPA joint experiment to study the onset, growth, and decay of relativistic electrons (REs) indicate that loss mechanisms other than collisional damping may play a dominant role in dynamics RE population, even during quiescent Ip flattop. Understanding physics growth mitigation is motivated by theoretical prediction disruptions full-current (15 MA) ITER discharges could generate up 10 MA REs with 10–20 MeV energies. The MHD group conducting measure detection threshold...
Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated recent research worldwide.Recent analysis has identified the current density profile as main drive disruptive instabilities simulating ITER's baseline scenario with low external torque.Ongoing development model-based active magnetohydrodynamic is improving stability multiple scenarios.Significant advances made toward physicsbased prediction...
A multi-device database of disruption characteristics has been developed under the auspices International Tokamak Physics Activity magneto-hydrodynamics topical group. The purpose this ITPA (IDDB) is to find commonalities between and mitigation in a wide variety tokamaks order elucidate physics underlying tokamak disruptions extrapolate toward much larger devices, such as ITER future burning plasma devices. In contrast previous smaller data collation efforts, IDDB aims provide significant...