A5015697952- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Astronomical Observations and Instrumentation
- Laser-induced spectroscopy and plasma
- Nuclear reactor physics and engineering
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Dust and Plasma Wave Phenomena
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Spacecraft and Cryogenic Technologies
- Inertial Sensor and Navigation
- X-ray Spectroscopy and Fluorescence Analysis
- Semiconductor materials and devices
- Diamond and Carbon-based Materials Research
- Electrostatic Discharge in Electronics
Princeton Plasma Physics Laboratory
2013-2024
Stellar Solutions (United States)
2024
Princeton University
1997-2021
University of Surrey
2020
Instituto de Ciencias Agrarias
2020
Arkansas Agricultural Experiment Station
2013
Kansas State University
2013
Garden City Community College
2012
NOAA National Weather Service
2012
Oak Ridge National Laboratory
1991-2011
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...
A multi-species fluid model is described for the steady state parallel and radial force balance equations in axisymmetric tokamak plasmas. The bootstrap current, electrical resistivity, particle heat fluxes are evaluated terms of rotation velocities friction viscosity coefficients. recent formulation neoclassical plasma arbitrary shape aspect ratio (including unity limit), collisionality, orbit squeezing from strong electric fields used to illustrate features model. current very low National...
A detailed comparison is made between the tearing-type modes observed in TFTR supershot plasmas and nonlinear, neoclassical pressure-gradient--driven tearing mode theory. Good agreement found on nonlinear evolution of single helicity magnetic islands $(m/n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2$, $4/3$, or $5/4$, where $m$ $n$ are poloidal toroidal numbers, respectively). The saturation these requires ${\ensuremath{\Delta}}^{\ensuremath{'}}<0$ (where...
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 ${10}^{16}$...
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...
Simultaneous profile measurements of the toroidal rotation speed and ion temperature during unbalanced neutral beam injection in Tokamak Fusion Test Reactor show that momentum thermal diffusivities are comparable magnitude (${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$\ensuremath{\approxeq}1.5${\mathrm{\ensuremath{\chi}}}_{\mathrm{i}}$) vary similarly with plasma current minor radius. The correlation ${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$...
Neutral-beam--heated plasmas in TFTR show evidence of substantial non-Ohmically driven toroidal current, even for balanced beam momentum input. The observations are inconsistent with calculations including only Ohmic and beam-driven currents, presently can be matched by models the neoclassical bootstrap current.
Compact optimized stellarators offer novel solutions for confining high-β plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures provide drift-orbit similar tokamaks. These configurations possibility of combining steady-state low-recirculating power, external control, disruption resilience previous with low aspect ratio, high β limit, good...
The confinement improvement in reversed-shear experiments on the Tokamak Fusion Test Reactor [Plasma Phys. Controlled 26, 11 (1984)] is investigated using nonlinear gyrofluid simulations including a bounce-averaged trapped electron fluid model. This model includes important kinetic effects for both ions and electrons, agrees well with linear theory. Both reversed shear Shafranov shift reverse precession drifts of large fraction which significantly reduces growth rate mode, found to be...
A transport code (TRANSP) is used to simulate future deuterium-tritium (DT) experiments in TFTR.The simulations are derived from 14 TFTR DD discharges, and the modelling of one supershot discussed detail indicate degree accuracy TRANSP modelling.Fusion energy yields 01 particle parameters calculated, including profiles slowing down time, average energy, AlfvBn speed frequency.Two types simulation discussed.The main emphasis on DT equivalent, where an equal mix D T substituted for initial...
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...
General plasma physics principles state that power flow Q(r) through a magnetic surface in tokamak should scale as Q(r)= {32π2Rr3Te2c nea/[eB (a2−r2)2]} F(ρ*,β,ν*,r/a,q,s,r/R,...) where the arguments of F are local, nondimensional parameters and gradients. This paper reports an experimental determination how varies with normalized gyroradius ρ*≡(2TeMi)1/2c/eBa collisionality ν*≡(R/r)3/2qRνe(me/ 2Te)1/2 for discharges prepared so other remain close to constant. Tokamak Fusion Test Reactor...
K\ensuremath{\alpha} x-ray spectra of heliumlike titanium, Ti xxi, from Tokamak Fusion Test Reactor (TFTR) plasmas have been observed with a high-resolution crystal spectrometer and used as diagnostic central plasma parameters. The data allow detailed comparison recent theoretical predictions for the xxi lines associated satellite spectrum in wavelength range 2.6000 to 2.6400 A\r{}. Improved values excitation rate coefficients resonance line, intercombination lines, forbidden new results on...
The time-scales for sawtooth repetition and heat pulse propagation are much longer (tens of milliseconds) in the large tokamak TFTR than previous, smaller tokamaks. This extended time-scale, coupled with more detailed diagnostics, has led us to revisit analysis as a method determine electron diffusivity χe plasma. A combination analytic computer solutions diffusion equation is used clarify previous work develop new methods determining χe. Direct comparison predicted pulses soft-X-ray ECE...
A potentially attractive next-step towards fusion commercialization is a pilot plant, i.e. device ultimately capable of small net electricity production in as compact facility possible and configuration scalable to full-size power plant. key capability for pilot-plant programme the high neutron fluence enabling nuclear science technology (FNST) research. It found that physics assumptions between those assumed ITER nth-of-a-kind it provide FNST-relevant wall loading devices. Thus, may be...
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...
A TFTR supershot with a plasma current of 2.5 MA, neutral beam heating power 33.7 MW, and peak DT fusion 7.5 MW is studied using the TRANSP analysis code.Simulations alpha parameters such as heating, pressure, distributions in energy Vparallel/ v are given.The effects toroidal ripple mixing fast particles during sawteeth observed after injection phase modeled.The on outer midplane peaked near fotward backward Vparalel / v. Ripple losses deplete vicinity Vpamllel/ f: -0.4.Sawtooth computed to...
Supershots in TFTR often suffer a performance deterioration characterized by gradual decrease of the DD fusion neutron yield and plasma stored energy after several hundred milliseconds auxiliary heating. The correlation between this development low m (the poloidal mode number), n toroidal number) MHD modes is studied through shot-to-shot comparisons statistical data analyses. A good observed appearance strong 3/2 4/3 macroscopic modes. magnetic island structures are using Mirnov ECE...
Momentum confinement was investigated on DIII-D as a function of applied neutral beam torque at constant normalized beta βN, by varying the mix co (parallel to plasma current) and counter beams. Under balanced injection (i.e. zero total plasma), maintains significant rotation in co-direction. This 'intrinsic' can be modeled being due an offset 'anomalous torque'). anomalous appears have magnitude comparable one source. The presence such source must taken into account obtain meaningful...
Measurements on the TFTR tokamak of electron-temperature-profile evolution and soft-x-ray emissivity a fast (10-\ensuremath{\mu}sec) time scale during sawtooth crash show that significant heat is deposited beyond mixing (or reconnection) radius within 200 \ensuremath{\mu}sec following crash. This extended region in which electron redistributed substantially complicates determination transport properties from subsequent pulse propagation. It shown relaxation this perturbation consistent with...
We consider the novel problem of optimizing a large set passive superconducting coils (PSCs) with currents induced by background magnetic field rather than power supplies. In nuclear fusion literature, such have been proposed to partially produce 3D fields for stellarators and provide stabilization. perform first optimizations PSC arrays respect orientation, shape, location each coil, jointly minimized fields. conclude generating coil array solutions four stellarators.
Toroidal Alfvén eigenmodes are shown to be capable of inducing ripple trapping high-energy particles in tokamaks, causing intense localized particle loss. The effect has been observed TFTR [R. Hawryluk, Plasma Phys. Controlled Fusion 33, 1509 (1991)].
The q-profile plays a key role in determining plasma equilibrium and stability tokamaks. With the development of motional Stark effect (MSE) diagnostic, accurate q(R,t) profiles have been measured utilized for analysis. A multichannel MSE polarimeter system on Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled 33, 1509 (1991)] has obtained data several conditions including L-mode, supershot, current ramps, high βp. For sawtoothing discharges TFTR, it is found that q(0)∼0.7, well...