A5039456936- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Atomic and Molecular Physics
- Atomic and Subatomic Physics Research
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Nuclear reactor physics and engineering
- Nuclear physics research studies
- X-ray Spectroscopy and Fluorescence Analysis
- Dust and Plasma Wave Phenomena
- Particle Accelerators and Free-Electron Lasers
- Radiation Detection and Scintillator Technologies
- Particle Detector Development and Performance
- Advanced NMR Techniques and Applications
- Silicon and Solar Cell Technologies
- Radioactive Decay and Measurement Techniques
- Semiconductor materials and devices
- Metal and Thin Film Mechanics
- Advanced Chemical Physics Studies
Princeton Plasma Physics Laboratory
2015-2024
Newcastle upon Tyne Hospitals NHS Foundation Trust
2024
Freeman Hospital
2024
Princeton University
2009-2023
University of Wisconsin–Madison
2013
Nova Photonics (United States)
2006-2012
Oak Ridge National Laboratory
1991-2012
University of Rochester
2006-2010
University of California, Irvine
2006-2009
General Atomics (United States)
2006-2009
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 coincidence circuit for use with anthracene or stilbene scintillation counters is described. Its resolving time lies in the 10 −9 sec. range, agreement theoretical estimates of minimum possible these counters. Examples are given measurement short gamma-ray half-lives and, conjunction beta-ray spectrometers, determination details radioactive disintegration schemes. The new results examples as follows:[Formula: see text]
Abstract The objectives of NSTX-U research are to reinforce the advantages STs while addressing challenges. To extend confinement physics low- A , high beta plasmas lower collisionality levels, understanding transport mechanisms that set performance and pedestal profiles is being advanced through gyrokinetic simulations, reduced model development, comparison NSTX experiment, as well improved simulation RF heating. develop stable non-inductive scenarios needed for steady-state operation,...
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...
Reduction or elimination of edge localized modes (ELMs) while maintaining high confinement is essential for future fusion devices, e.g., the ITER. An ELM-free regime was recently obtained in National Spherical Torus Experiment, following lithium (Li) evaporation onto plasma-facing components. Edge stability calculations indicate that pre-Li discharges were unstable to low-$n$ peeling ballooning modes, broader pressure profiles stabilized post-Li discharges. Normalized energy increased by 50%...
National Spherical Torus Experiment [which M. Ono et al., Nucl. Fusion 40, 557 (2000)] high-power divertor plasma experiments have shown, for the first time, that benefits from lithium coatings applied to facing components found previously in limited plasmas can occur also diverted configurations. Lithium were with pellets injected into helium discharges, and an oven directed a collimated stream of vapor toward graphite tiles lower center stack divertor. depositions few milligrams 1g been...
The time distribution of the annihilation radiation emerging from liquids and solids, following absorption by samples fast positrons, has been studied delayed coincidence method. mean life positrons in metals is found to be about 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}10}$ sec, nearly independent metal chosen. Some simple crystals behave similarly, but many amorphous substances, both solid liquid, show a complex decay which $\frac{2}{3}$ annihilate with few times...
This Letter presents nonlinear gyrokinetic simulations of microtearing mode turbulence. The include collisional and electromagnetic effects use experimental parameters from a high-β discharge in the National Spherical Torus Experiment. predicted electron thermal transport is comparable to that given by analysis, it dominated contribution electrons free-streaming along resulting stochastic magnetic field line trajectories. Experimental values flow shear can significantly reduce transport.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation and Characterization of a New Crystalline Form Molybdenum DisulfideRonald E. Bell Robert HerfertCite this: J. Am. Chem. Soc. 1957, 79, 13, 3351–3354Publication Date (Print):July 1, 1957Publication History Published online1 May 2002Published inissue 1 July 1957https://doi.org/10.1021/ja01570a012RIGHTS & PERMISSIONSArticle Views1375Altmetric-Citations94LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum full text article...
Abstract Lithium wall coatings have been shown to reduce recycling, suppress edge-localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document effect of gradually increasing lithium on discharge characteristics, with reference ELMy discharges obtained boronized, i.e. non-lithiated conditions. We observed a continuous but not quite monotonic reduction recycling improvement confinement, gradual alteration edge plasma profiles,...
Radiation exposure during fluoroscopically guided interventions such as endovascular aortic repair (EVAR) is a growing concern for operators. This study aimed to measure DNA damage/repair markers in operators perfoming EVAR.Expression of the marker, γ-H2AX and damage response phosphorylated ataxia telangiectasia mutated (pATM), were quantified circulating lymphocytes peri-operative period (infrarenal, branched, fenestrated) open using flow cytometry. These separately measured same but this...
A number of magnetic dipole γ-ray transitions have been studied using a coincidence circuit short resolving time (2τ 0 = 2 × 10 −9 sec), two lens single β-ray spectrometer, pair spectrometers placed end to with counting the focused radiations from source, and scintillation spectrometer. Lifetimes measured delayed method where feasible conversion coefficients K/L ratios obtained. Comparison is made theoretical estimates lifetime–energy relation for M1 transitions.The new results are as...
Disruption prediction and avoidance is a critical need for next-step tokamaks, such as ITER. Event Characterization Forecasting (DECAF) research fully automates analysis of tokamak data to determine chains events that lead disruptions forecast their evolution allowing sufficient time mitigation or complete the disruption. event related local rotating global magnetohydrodynamic (MHD) modes vertical instability are examined with warnings issued many off-normal physics events, including density...
Research in NSTX has been conducted to establish spherical torus plasmas be used for high β, auxiliary heated experiments. This device a major radius R0 = 0.86 m and midplane halfwidth of 0.7 m. It operated with toroidal magnetic field B0 ⩽ 0.3 T Ip 1.0 MA. The evolution the plasma equilibrium is analysed between discharges an automated version EFIT code. Limiter, double null lower single diverted configurations have sustained several energy confinement times. stored reached 92 kJ (βt 17.8%)...
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...
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...
The National Spherical Torus Experiment (NSTX) has demonstrated the advantages of low aspect ratio geometry in accessing high toroidal and normalized plasma beta, βN ≡ 108⟨βt⟩ aB0/Ip. Experiments have reached βt = 39% 7.2 through boundary profile optimization. High plasmas can exceed ideal no-wall stability limit, βNno−wall, for periods much greater than wall eddy current decay time. Resistive mode (RWM) physics is studied to understand stabilization these plasmas. spectrum unstable RWMs...
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...
Recent experiments (Synakowski et al 2004 Nucl. Fusion 43 1648, Lloyd Plasma Phys. Control. 46 B477) on the Spherical Tokamak (or Torus, ST) (Peng 2000 Plasmas 7 1681) have discovered robust plasma conditions, easing shaping, stability limits, energy confinement, self-driven current and sustainment. This progress has encouraged an update of conditions engineering a Component Test Facility (CTF), (Cheng 1998 Eng. Des. 38 219) which is very valuable step in development practical fusion energy....
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...
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...
Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on performance of divertor plasmas as a result applying lithium coatings graphite and carbon-fiber-composite plasma-facing components. These mostly been applied by pair evaporators mounted at top vacuum vessel which inject collimated streams vapor toward lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode run immediately after application lithium, modifications included decreases...