F. M. Levinton
A5089913632- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Geomagnetism and Paleomagnetism Studies
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Laser Design and Applications
- Magnetic Field Sensors Techniques
- Spectroscopy and Laser Applications
- Laser-Matter Interactions and Applications
- Advanced Fiber Laser Technologies
- Dust and Plasma Wave Phenomena
- Quantum chaos and dynamical systems
- Photonic and Optical Devices
- Fluid Dynamics and Turbulent Flows
- High-pressure geophysics and materials
- Quantum, superfluid, helium dynamics
Nova Photonics (United States)
2009-2024
Princeton University
1997-2013
Princeton Plasma Physics Laboratory
1994-2012
Columbia University
1983-2007
Oak Ridge National Laboratory
1994-2007
University of Washington
2006-2007
University of Baltimore
2006-2007
Johns Hopkins University
2006-2007
General Atomics (United States)
1997-2006
Massachusetts Institute of Technology
1994-2006
A new tokamak confinement regime has been observed on the Tokamak Fusion Test Reactor (TFTR) where particle and ion thermal diffusivities drop precipitously by a factor of \ensuremath{\sim}40 to neoclassical level for particles much less than value ions in region with reversed shear. This enhanced shear mode allows central electron density rise from 0.45 \ifmmode\times\else\texttimes\fi{} ${10}^{20}$ ${\mathrm{m}}^{\ensuremath{-}3}$ \ensuremath{\sim}1.2 ${T}_{i}\ensuremath{\sim}24$ keV...
Polarimetry measurements of the Doppler-shifted ${\mathrm{H}}_{\mathrm{\ensuremath{\alpha}}}$ emission from a neutral hydrogen beam on PBX-M tokamak have been employed in novel technique for obtaining q(r) and magnetic field pitch-angle profiles using Stark effect. The resulting profile is very broad its central value, q(0), significantly below 1, which has important implications theoretical models sawteeth.
Neutral-beam heating of plasmas in the Tokamak Fusion Test Reactor at low preinjection densities [${n}_{e}$(0)\ensuremath{\simeq}${10}^{19}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$] were characterized by ${T}_{e}$(0)=6.5 keV, ${T}_{i}$(0)=20 ${n}_{e}$(0)=7\ifmmode\times\else\texttimes\fi{}${10}^{19}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$, ${\ensuremath{\tau}}_{E}$=170 msec, ${\ensuremath{\beta}}_{\mathrm{theta}}$=2, and a d(d,n${)}^{3}$He neutron emission rate ${10}^{16}$...
Dissipation of plasma toroidal angular momentum is observed in the National Spherical Torus Experiment due to applied nonaxisymmetric magnetic fields and their plasma-induced increase by resonant field amplification resistive wall mode destabilization. The measured decrease profile compared calculations nonresonant drag torque based on theory neoclassical viscosity. Quantitative agreement between experiment found when effect toroidally trapped particles included.
Turbulent fluctuations in plasmas with reversed magnetic shear have been investigated on the Tokamak Fusion Test Reactor. Under intense auxiliary heating, these are observed to bifurcate into two states different transport properties. In state better confinement, it has found that level of is very small throughout most region negative shear. By contrast, lower confinement characterized by large bursts which suggest a competition between driving and suppression turbulence. These results...
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...
Using laser-induced fluorescence, measurements have been made of metastable argon-ion, Ar+*(3d4F7/2), velocity distributions on the major axis an axisymmetric magnetic-mirror device whose plasma is sustained by helicon wave absorption. Within mirror, these ions sub-eV temperature and, at most, a subthermal axial drift. In region outside mirror coils, conditions are found where field-parallel above acoustic speed, to energy ∼30 eV, while ion remains low. The supersonic Ar+*(3d4F7/2)...
Off-axis sawteeth are often observed in reversed magnetic shear plasmas when the minimum safety factor $q$ is near or below 2. Fluctuations with $m/n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2/1$ ( $m$ and $n$ poloidal toroidal mode numbers) appear before after crashes. Detailed comparison has been made between measured ${T}_{e}$ profile evaluation during crash a nonlinear numerical magnetohydrodynamics simulation. The good agreement observation simulation indicates that off-axis...
Peak fusion power production of 6.2\ifmmode\pm\else\textpm\fi{}0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total 29.5 MW. These have an inferred central alpha particle density 1.2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$ without the appearance either disruptive magnetohydrodynamics events or detectable changes Alfv\'en wave activity. The measured loss rate energetic particles agreed with...
In this paper a laboratory investigation is made on magnetic reconnection in high-temperature Tokamak Fusion Test Reactor (TFTR) plasmas [Plasma Physics and Controlled Nuclear Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 51]. The motional Stark effect (MSE) diagnostic employed to measure the pitch angle profile of field lines, hence q profile. An analytical expression that relates presented for toroidal plasma with circular cross section. During crash phase...
The resistive-wall mode is actively stabilized in the National Spherical Torus Experiment high-beta plasmas rotating significantly below critical rotation speed for passive stability and range predicted International Thermonuclear Experimental Reactor. Variation of feedback stabilization parameters shows excitation or suppression. Stabilization toroidal number unity did not lead to instability two. can become unstable by deforming poloidally, an important consideration system design.
Stabilizing modes that limit plasma beta and reduce their deleterious effect on rotation are key goals for the efficient operation of a fusion reactor. Passive stabilization active control global kink/ballooning resistive wall (RWMs) have been demonstrated NSTX research is now advancing towards understanding physics reliably maintaining high confident extrapolation to ITER component test facility based spherical torus. Active n = 1 experiments with an expanded sensor set, combined low levels...
The NSTX operates at low aspect ratio (R/a ∼ 1.3) and high beta (up to 40%), allowing tests of global confinement local transport properties that have been established from higher devices. plasmas are heated by up 7 MW deuterium neutral beams with preferential electron heating as expected for ITER. Confinement scaling studies indicate a strong BT dependence, current dependence is weaker than observed ratio. Dimensionless experiments increase in decreasing collisionality weak degradation...
Alpha-particle-driven toroidal Alfvén eigenmodes (TAEs) have been observed for the first time in deuterium-tritium (D-T) plasmas on tokamak fusion test reactor (TFTR). These modes are 100–200 ms following end of neutral beam injection with reduced central magnetic shear and elevated safety factor [q0>1]. Mode activity is localized to region discharge r/a<0.5 fluctuation level B̃⊥/B∥∼10−5 mode numbers range n=2–4, consistent theoretical calculations α-TAE stability TFTR.Received 11 November...
The relaxation of core transport barriers in TFTR enhanced reversed shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range shear, but increase when local $\mathbf{E}\ifmmode\times\else\texttimes\fi{}\mathbf{B}$ shearing are driven below threshold comparable to fastest linear growth dominant instabilities. Shafranov-shift-induced stabilization alone is not...
A bifurcation in the core poloidal rotation of carbon impurity ions Tokamak Fusion Test Reactor (TFTR) has been observed prior to transport associated with enhanced reverse shear plasmas. In a narrow radial region plasma, ion reverses direction. This flow is establishment large negative electric field strong shear. The measured velocities before, during, and after this precursor differ from neoclassical predictions.
The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove D. M. Meade, Nucl. 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis a positive-feedback model that predicts reinforced suppression with increasing pressure gradient. Local fluctuation behavior at onset ERS confinement is consistent this framework. power required transitions into regime lower when...
Although the q profile plays a key role in theories of instabilities and plasma equilibrium, it has been quite difficult to measure until recent development motional Stark effect (MSE) diagnostic. A multichannel polarimeter system recently installed on Tokamak Fusion Test Reactor (TFTR). The diagnostic can magnetic field pitch angle [γp=tan−1(Bp/BT)] at ten radial locations. doppler shifted Dα radiation from TFTR heating beam is viewed near tangential toroidal via re-entrant front surface...
A wide variety of fast ion driven instabilities are excited during neutral beam injection (NBI) in the National Spherical Torus Experiment (NSTX) [Nucl. Fusion 40, 557 (2000)] due to large ratio velocity Alfvén velocity, Vfast∕VAlfvén, and high beta. The Vfast∕VAlfvén ITER 39, 2137 (1999)] NSTX is comparable. modes can be divided into three categories: chirping energetic particle (EPM) frequency range 0 120kHz, toroidal eigenmodes (TAE) with a 50kHz 200kHz, compressional global (CAE GAE,...
After many years of fusion research, the conditions needed for a D–T reactor have been approached on Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For first time unique phenomena present in plasma are now being studied laboratory plasma. The magnetic experiments to study plasmas using nearly equal concentrations deuterium and tritium carried out TFTR. At maximum power 10.7 MW, 39.5 MW neutral-beam heating, supershot discharge 6.7 high-βp following current rampdown....
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...
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 Tokamak Fusion Test Reactor (TFTR) (R. J. Hawryluk, to be published in Rev. Mod. Phys.) experiments on high-temperature plasmas, that culminated the study of deuterium–tritium D–T plasmas containing significant populations energetic alpha particles, spanned over two decades from conception completion. During design TFTR, key physics issues were magnetohydrodynamic (MHD) equilibrium and stability, plasma energy transport, impurity effects, reactivity. Energetic particle was given less...
The Tomamak Fusion Test reactor has performed initial high-power experiments with the plasma fueled nominally equal densities of deuterium and tritium. Compared to pure plasmas, energy stored in electron ions increased by \ensuremath{\sim}20%. These increases indicate improvements confinement associated use tritium possibly heating electrons \ensuremath{\alpha} particles created D-T fusion reactions.
A motional Stark effect diagnostic has been utilized to reconstruct the parallel current density profile in a spherical-torus plasma for first time. The measured compares favorably with neoclassical theory when no large-scale magnetohydrodynamic instabilities are present plasma. However, anomaly is observed during saturated interchange-type instability activity. This apparent can be explained by redistribution of neutral beam injection drive and represents observation causing such...