Cris W. Barnes
A5055107070- Magnetic confinement fusion research
- Nuclear Physics and Applications
- Laser-Plasma Interactions and Diagnostics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Radiation Detection and Scintillator Technologies
- Nuclear reactor physics and engineering
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Atomic and Subatomic Physics Research
- Laser-Matter Interactions and Applications
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Atomic and Molecular Physics
- Neural Networks and Applications
- Radiation Therapy and Dosimetry
- Laser Design and Applications
- Combustion and Detonation Processes
- Advanced X-ray and CT Imaging
- Radioactive contamination and transfer
- Advanced X-ray Imaging Techniques
- Planetary Science and Exploration
- Particle Accelerators and Free-Electron Lasers
- X-ray Spectroscopy and Fluorescence Analysis
Los Alamos National Laboratory
2013-2022
Institute for Atomic and Molecular Physics
2005
Dutch Polymer Institute
2005
Eindhoven University of Technology
2005
Boston Children's Hospital
2005
Harvard University
2005
École Polytechnique Fédérale de Lausanne
2005
Czech Academy of Sciences, Institute of Macromolecular Chemistry
2005
Circle (United States)
2005
Tokyo Polytechnic University
2005
For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as proof of principle various concepts. Following Lawson criterion, an ignited plasma is one where heating power high enough overcome all physical processes that cool plasma, creating positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, state can begin "burn propagation" into surrounding cold fuel, enabling possibility energy...
Two new gated x-ray imaging cameras have recently been designed, constructed, and delivered to the National Ignition Facility in Livermore, CA. These x-Ray detectors are each designed fit within an aluminum airbox with a large capacity cooling plane fitted array of environmental housekeeping sensors. instruments significantly different from earlier generations images due, part, innovative impedance matching scheme, advanced phosphor screens, pulsed circuits, precision assembly fixturing,...
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...
Two steps have been taken towards determining if the flux absorption and relaxation properties of a spheromak will allow dc-powered electrodes to form sustain steady-state spheromak. Without changing physical spheromak, formation time was increased from an Alfv\'en tearing time, reducing coaxial source power \ensuremath{\sim} 10 GW 500 MW. With use 50 MW, spheromaks were formed then sustained at constant density field for 1 ms, much longer than magnetic-energy decay time.
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...
Experimental spheromak magnetic equilibria are measured which differ significantly from the minimum-energy state, and well described by a numerical model where ${j}_{?}$/B has linear dependence on poloidal flux function. Equilibria determined in nonperturbing manner combination of measurements flux-conserver image currents with calculations this model. These corroborated observation nondisruptive rotating internal kink distortions (with toroidal mode numbers n=1, 2, 3), coupled theoretical...
Neural networks are examined in the context of function approximation and related field time series prediction. A natural extension radial basis nets is introduced. It found that use an adaptable gradient normalized functions can significantly reduce amount data necessary to train net while maintaining speed advantage a linear weights. The local nature network permits simple learning algorithms with short memories earlier training data. In particular, it shown one-dimensional Newton method...
The conjecture that magnetic helicity (linked flux) is conserved in magnetized plasmas for time scales are short compared to the resistive diffusion experimentally tested CTX spheromak [Phys. Rev. Lett. 45, 1264 (1980); 51, 39 (1983); Nucl. Fusion 24, 267 (1984)]. Helicity created electrostatically by current drawn from electrodes. plasma then flows into a conducting flux conserver where energy per of minimized and formed on relaxation scale many Alfvén times. field strength equilibrium...
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....
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.
Absolutely calibrated measurements of the neutron yield are important for evaluation plasma performance such as fusion gain Q in D–D operating tokamaks. The time-resolved is measured with 235U and 238U fission chambers 3He proportional counters JT-60U tokamak. situ calibration was performed by moving 252Cf source toroidally through JT-60 vacuum vessel. Detection efficiencies three two detectors were 92 locations point toroidal scans at different major radii. total detection efficiency torus...
Electrostatic (dc) helicity injection has previously been shown to successfully sustain the magnetic fields of spheromaks and tokamaks. The magnitude injected balances (within experimental error) flux lost by resistive decay toroidal equilibrium. Hence problem optimizing this current drive scheme involves maximizing (the voltage-connecting-flux product) while minimizing (which multiplied voltage represents energy input also possible damage electrodes). impedance (voltage-to-current ratio)...
The evolution of the density profile in PLT during intense gas puffing is documented and analysed. Measurements spectrum low-energy edge neutrals change central neutral density, indicate that charge-exchange processes alone cannot account for rise. transient changes can be reproduced numerically by a diffusivity ∼ 104 cm2·s−1 spatially averaged inward flow 103 cm·s−1. These transport coefficients are 10—102 times larger than neoclassical. ion energy confinement reduced, small-scale...
The Rayleigh–Taylor instability is an important limitation in inertial confinement fusion capsule designs. Significant work both theoretically and experimentally has been done to demonstrate the stabilizing effects of material flow through unstable region. experimental verification predominantly planar geometry. Convergent geometry introduces not present such as shell thickening accelerationless growth modal amplitudes (e.g., Bell–Plesset growth). Amplitude thresholds for nonlinear regime...
We report results of the TFTR fission detector calibration performed in December 1988. A NBS-traceable, remotely controlled 252Cf neutron source was moved toroidally through vacuum vessel. Detection efficiencies for two 235U detectors were measured 930 locations point toroidal scans at 16 different major radii and vertical heights. These effectively simulated volume-distributed plasma volume-integrated detection efficiency found to be insensitive position. The Campbell mode is useful due its...
A review of TFTR plasma transport studies is presented. Parallel and the confinement suprathermal ions are found to be relatively well described by theory. Cross-field thermal plasma, however, anomalous with momentum diffusivity being comparable ion larger than electron in neutral beam heated discharges. Perturbative experiments have studied nonlinear dependencies coefficients examined role possible nonlocal phenomena. The underlying turbulence has been using microwave scattering, emission...
Circular-limiter H modes are obtained on the TFTR tokamak during high-power neutral-beam heating. The transition is usually from supershot to mode rather than usual L transition, and thus in a low-recycling environment with core fueling mainly heating beams. As result, density pressure profiles highly peaked at center. global confinement time ${\mathrm{\ensuremath{\tau}}}_{\mathit{E}}$ enhanced over L-mode scaling by up \ensuremath{\approxeq}2.5 times. onset of edge-localized MHD shortly...
The confinement and heating of supershot plasmas are significantly enhanced with tritium beam injection relative to deuterium in the Tokamak Fusion Test Reactor [Plasma Phys. Controlled 26, 11 (1984)]. global energy local thermal transport analyzed for fueled quantify their dependence on average mass hydrogenic ions. Radial profiles densities determined from D–T fusion neutron emission profile. inferred scalings isotopic quite strong, τE∝〈A〉0.85±0.20, τEthermal∝〈A〉0.89±0.20,...
Empirical scaling expressions, reflecting the parametric dependence of L-mode energy confinement time, have been used not only as benchmarks for tokamak operation and theories transport, but predicting performance proposed devices. Several expressions based on data from small medium sized devices done well in larger devices, although great uncertainty exists extrapolating yet further, into ignition regime. approaches exist developing higher confidence expressions. These include reducing...
Recently a new high energy proton microscopy facility PRIOR (Proton Microscope for FAIR) has been designed, constructed and successfully commissioned at GSI Helmholtzzentrum f\"ur Schwerionenforschung (Darmstadt, Germany). As result of the experiments with 3.5-4.5 GeV beams delivered by heavy ion synchrotron SIS-18 GSI, 30 um spatial 10 ns temporal resolutions microscope have demostrated. A pulsed power setup studying properties matter under extremes developed dynamic commissioning facility....
Laser beams that directly drive a cylindrical implosion are used to create measurable region of mixed material in compressible plasma state, for the first time convergent geometry. The turbulence driven by Richtmyer–Meshkov instability shock passage across density discontinuity mixes marker is radiographically opaque. width mix layer compared between system with large surface roughness and an initially smooth system. experiment described results multi-dimensional numerical simulation,...