A5055896327- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Gyrotron and Vacuum Electronics Research
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Electromagnetic Launch and Propulsion Technology
- Atomic and Molecular Physics
- Semiconductor materials and devices
- Dust and Plasma Wave Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Laser-induced spectroscopy and plasma
- Advancements in Semiconductor Devices and Circuit Design
- Electrostatic Discharge in Electronics
- Advanced Data Storage Technologies
- Silicon Carbide Semiconductor Technologies
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- Electric Motor Design and Analysis
CompX (United States)
2016-2025
Princeton Plasma Physics Laboratory
1990-2012
Oak Ridge National Laboratory
2001-2012
Fusion Academy
2001-2012
Fusion (United States)
2001-2012
Plasma Technology (United States)
2001-2012
Lomonosov Moscow State University
2012
General Atomics (United States)
1995-2010
Massachusetts Institute of Technology
2006-2010
University of California, Irvine
2006-2010
The maximum normalized beta achieved in long-pulse tokamak discharges at low collisionality falls significantly below both that observed short pulse and predicted by the ideal MHD theory. Recent experiments, particular those simulating International Thermonuclear Experimental Reactor (ITER) [M. Rosenbluth et al., Plasma Physics Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1995), Vol. 2, p. 517] scenarios with νe*, are often limited low-m/n nonideal...
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 Wisconsin high-temperature superconductor axisymmetric mirror experiment (WHAM) will be a high-field platform for prototyping technologies, validating interchange stabilization techniques and benchmarking numerical code performance, enabling the next step up to reactor parameters. A detailed overview of experimental apparatus its various subsystems is presented. WHAM use electron cyclotron heating ionize build dense target plasma neutral beam injection fast ions, stabilized by...
Optimal design and use of electron cyclotron heating requires that accurate relatively quick computer codes be available for prediction wave coupling, propagation, damping current drive at realistic levels EC power. To this end, a number have been developed in laboratories worldwide. A detailed comparison these is desirable since they variety methods modelling the behaviour effects waves. The approach used benchmarking study to apply small representative cases. Following minor remedial work...
A conservative transport operator in ($r$,${v}_{\ensuremath{\parallel}}$,${v}_{\ensuremath{\perp}}$) space and moment equations are derived which describe the combined effects of a stochastic magnetic field radial electric on electrons. The is coupled with Fokker-Planck Ohmic-heating terms to compute distribution function. physical picture emerges emphasizes possible importance ambipolar potential ($\ensuremath{\sim}\frac{{T}_{e}}{e}$) plasma boundary physics determining overall confinement.
Combined neutral beam injection and fast wave heating at the fourth fifth cyclotron harmonics accelerate ions in DIII-D tokamak. Measurements with a nine-channel fast-ion D-alpha (FIDA) diagnostic indicate formation of tail above energy. Tail correlates enhancement d–d neutron rate value that is expected absence fast-wave acceleration. FIDA spatial profiles pressure inferred from equilibrium both acceleration near magnetic axis for centrally located resonance layer. The largest 8–10 cm...
Experimental evidence is reported of an internal kink instability driven by a new mechanism: barely trapped suprathermal electrons produced off-axis electron cyclotron heating on the DIII-D tokamak. It occurs in plasmas with evolving safety factor profile q(r) when q(min) approaches 1. This most active ECCD applied high field side flux surface. has bursting behavior poloidal/toroidal mode number = m/n 1/1. In positive magnetic shear plasmas, this becomes fishbone instability. observation can...
The scaling of cross-field heat transport with relative gyroradius ρ* was measured in low (L) and high (H) mode tokamak plasmas using the technique dimensionally similar discharges. scalings electron ion thermal diffusivities were determined separately a two-fluid analysis. For L-mode plasmas, diffusivity scaled as χe∝χBρ1.1±0.3* (gyro-Bohm-like) while χi∝χBρ−0.5±0.3* (worse than Bohm-like). results independent method auxiliary heating (radio frequency or neutral beam). Since fluids had...
Lower hybrid (LH) waves (Ωci⪡ω⪡Ωce, where Ωi,e≡Zi,eeB/mi,ec) have the attractive property of damping strongly via electron Landau resonance on relatively fast tail electrons and consequently are well-suited to driving current. Established modeling techniques use Wentzel–Kramers–Brillouin (WKB) expansions with self-consistent non-Maxwellian distributions. Higher order WKB shown some effects parallel wave number evolution due diffraction [G. Pereverzev, Nucl. Fusion 32, 1091 (1991)]. A...
High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup sustainment of spherical torus plasma. Considerable enhancement core efficiency (η) from 44% to 65% has been obtained CD phasing antenna (strap-to-strap ϕ=−90°, kϕ=−8m−1) by increasing magnetic field 4.5to5.5kG. This increase in is strongly correlated moving location onset density perpendicular propagation...
Experimental observations of lower hybrid current drive (LHCD) at high density on the Alcator C-Mod tokamak are presented in this paper. Bremsstrahlung emission from relativistic fast electrons core plasma drops suddenly above line-averaged densities 10 20 m −3 (ω/ω LH ∼ 3) single null discharges with large (⩾8 mm) inner gaps, well below limit previously observed limited tokamaks 2). Modelling and experimental evidence suggest that absence LHCD driven may be due to parasitic collisional...
Statistical studies have been made of the diurnal and latitudinal occurrence intensity patterns ELF, VLF, LF whistler-mode noise emissions observed with Alouette 2 satellite. The ELF occur characteristically below 1 kHz, are peculiar to daylight hours, show a peak in average invariant latitude range 50°–70°. In VLF range, broadband extending upward from LHR frequency maximum near local noon Λ about 77°. Along auroral oval toward earlier later they decreasing intensity. apparent...
Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique operational space is leveraged test theories next-step tokamak operation, including ITER. Present research also examines implications coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified varied wall conditions exhibits strong improvement of BTτE with decreased electron...
The detection of fast particle-driven waves in the ion cyclotron frequency range (ion emission or ICE) could provide a passive, non-invasive diagnostic confined and escaping particles (fusion α-particles beam ions) ITER, would be compatible with high radiation environment deuterium–tritium plasmas that device. Recent experimental results from ASDEX Upgrade DIII-D demonstrate efficacy ICE as different species losses, while recent particle-in-cell (PIC) hybrid simulations more exact comparison...
The time-dependent bounce-averaged CQL3D flux-conservative finite-difference Fokker–Planck equation (FPE) solver has been upgraded to include finite-orbit-width (FOW) capabilities which are necessary for an accurate description of neoclassical transport, losses the walls, and transfer particles, momentum, heat scrape-off layer. FOW modifications implemented in formulation neutral beam source, collision operator, RF quasilinear diffusion synthetic particle diagnostics. collisional radial...
The kinetic stability of collisionless, sloshing beam-ion (\(45^{\circ}\) pitch angle) plasma is studied in a 3D simple magnetic mirror, mimicking the Wisconsin High-temperature superconductor Axisymmetric Mirror (WHAM) experiment. collisional Fokker-Planck code CQL3D-m provides slowing-down distribution to initialize kinetic-ion/fluid-electron Hybrid-VPIC, which then simulates free decay without external heating or fueling. Over \(1\)–\(10\;\mathrm{\mu s}\), drift-cyclotron loss-cone (DCLC)...
Localized currents due to electron cyclotron current drive have been measured for the first time in experiments on DIII-D tokamak. The location of driven plasma has varied from near center tokamak out half minor radius. efficiency agrees with quasilinear Fokker-Planck calculations and exceeds predicted value increasing Reduction trapped fraction finite collisionality is a leading candidate explain discrepancy.
Runaway electrons are calculated to be produced during the rapid plasma cooling resulting from “killer pellet” injection experiments, in general agreement with observations DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] tokamak. The time-dependent dynamics of kinetic runaway distributions obtained CQL3D [R. W. Harvey M. G. McCoy, “The Code,” Proceedings IAEA Technical Committee Meeting...
The paper presents calculations of the efficiency fast wave current drive at reactor-like densities and temperatures, including toroidal effects. Accessibility competitive absorption mechanisms are estimated. Two bands frequencies found to be interest for reactor applications – one in ion cyclotron range other higher harmonics but below lower hybrid frequency.
A new relativistic, bounce-averaged Fokker-Planck-quasilinear code shows that for experimentally relevant rf power $\frac{{p}_{\mathrm{rf}}(\mathrm{W}/{\mathrm{cm}}^{3})}{{[{n}_{e}({10}^{13} {\mathrm{cm}}^{\ensuremath{-}3})]}^{2}}\ensuremath{\gtrsim}0.5$, electron-cyclotron current-drive efficiency (and absorptivity) is dependent; at given plasma radius the increases above linear values absorption of on low-field side cyclotron resonance layer, but decreases and even passes through zero...
This paper reviews the physics and technology of wave-particle-interaction experiments in ion cyclotron range frequencies (ICRF) lower hybrid (LH) (LHRF) on Alcator C-Mod tokamak. Operation fixed frequency (80 MHz) tunable (40- to 80-MHz) ICRF transmitters associated transmission system is described. Key fabrication issues that were solved order operate a four-strap antenna compact environment are discussed some detail. heating utilizing hydrogen (H) helium-3 (3He) minority schemes...
The avalanche of runaway electrons in an ohmic tokamak plasma triggered by knock-on collisions traces energetic with the bulk is simulated bounce averaged Fokker-Planck code, CQL3D. It shown that even when electric field small for production Dreicer runaways, can produce significant a fraction second at typical reactor parameters. energy spectrum these runaways has characteristic temperature. growth rate and temperature distribution are determined compared theory. In simulations pellet...
Electron cyclotron current drive (ECCD) experiments on the DIII-D tokamak are solidifying physics basis for localized, off-axis drive, goal being to validate a predictive model ECCD. The ECCD profiles determined from magnetic field pitch angles measured by motional Stark effect polarimetry. switches co- counter-direction as toroidal injection angle is varied with profile width that in accordance ray tracing calculations. Tests of electron trapping low beta plasmas show efficiency decreases...
A two-dimensional integral full-wave model is used to calculate poloidal forces driven by mode conversion in tokamak plasmas. In the presence of a magnetic field, near ion-ion hybrid resonance dominated transition from fast magnetosonic wave slow ion cyclotron wave. The field generates strong variations parallel spectrum that cause damping narrow layer surface. resulting this drive sheared flows comparable those direct launch Bernstein experiments.