A5022547833- Laser-Plasma Interactions and Diagnostics
- Nuclear Physics and Applications
- Laser-induced spectroscopy and plasma
- Laser-Matter Interactions and Applications
- Magnetic confinement fusion research
- High-pressure geophysics and materials
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Atomic and Molecular Physics
- Combustion and Detonation Processes
- Laser Design and Applications
- Particle Accelerators and Free-Electron Lasers
- Particle physics theoretical and experimental studies
- Muon and positron interactions and applications
- Ion-surface interactions and analysis
- Radiation Therapy and Dosimetry
- Particle accelerators and beam dynamics
- Neutrino Physics Research
- Nuclear reactor physics and engineering
- Cold Fusion and Nuclear Reactions
- Energetic Materials and Combustion
- Radioactive contamination and transfer
- Particle Detector Development and Performance
- Geological and Geophysical Studies
- Advanced X-ray Imaging Techniques
Los Alamos National Laboratory
2015-2024
University of Miami
2024
University of New Brunswick
2023
University of Fredericton
2023
Massachusetts Institute of Technology
1986-2022
American Institute of Aeronautics and Astronautics
2021
ORCID
2021
Watertown City School District
2019
University of Michigan
2018
Lawrence Livermore National Laboratory
1992-2018
A plate tectonic model for the Caledonides of British Isles with three non-parallel lower Ordovician-lower Devonian subduction systems is presented. In north-west, Caledonian thrust front interpreted as site multiple, slow ESE.-directed (Sd1) Lewisian-bearing continental foreland beneath crust containing an ensialic Dalradian basin. South Southern Uplands zone lay a ENE.–WSW.-trending boundary (Sd2) where Iapetus oceanic was subducted to NNW. The convergence lithosphere Moine-Dalradian...
The use of positrons in laboratory plasma physics experiments is considered. Recent progress this area discussed, including the creation a single-component positron laboratory. Specific applications such antimatter plasmas are also with emphasis on areas where existing technology and that currently under development likely to produce results next few years.
Positrons from a radioactive source are slowed to electron-volt energies and accumulated stored in trap which uses magnetic field for radial confinement an electrostatic well axial confinement. The positrons lose energy become trapped through inelastic collisions with nitrogen molecules introduced into the this purpose. has three stages progressively lower pressure. It is found that trapping each stage due primarily electronic excitation of molecules, loss being approximately 9 eV per...
It now appears feasible to deposit positrons (e+) in a tokamak plasma by injecting bursts of neutral positronium atoms (e+e−), which are then ionized the plasma. The annihilation time these is long compared with typical particle containment times. Thus subsequent transport can be studied monitoring dependence annihilation, gamma radiation produced when strike limiter. This paper discusses design such an experiment, kinds data obtained, and physics questions this experiment might address....
An absolute value has been obtained for the isotopic abundance ratio of a reference sample rhenium, using surface emission mass spectrometry. Samples known composition, prepared from nearly isotopically pure separated rhenium isotopes, were used to calibrate spectrometers. The resulting 185Ke/187Re is 0.59738±0.00039, which yields atom percents 185Re = 37.398±0.016 and 187Re 62.602±0.016. atomic weight calculated this composition 186.20679±0.00031. indicated uncertainties are overall limits...
DT neutron yield (Y(n)), ion temperature (T(i)), and down-scatter ratio (dsr) determined from measured spectra are essential metrics for diagnosing the performance of inertial confinement fusion (ICF) implosions at National Ignition Facility (NIF). A suite neutron-time-of-flight (nTOF) spectrometers a magnetic recoil spectrometer (MRS) have been implemented in different locations around NIF target chamber, providing good implosion coverage complementarity required reliable measurements Y(n),...
Measuring the width of energy spectrum fusion-produced neutrons from deuterium (DD) or deuterium-tritium (DT) plasmas is a commonly used method for determining ion temperature in inertial confinement fusion (ICF) implosions. In plasma with Maxwellian distribution energies, spread neutron arises thermal center-of-mass velocities reacting pairs ions. Fluid ICF are similar magnitude as and can lead to further broadening spectrum, leading erroneous inference temperature. Motion will affect DD DT...
Capsule implosion experiments carried out on the Nova laser [E. M. Campbell et al., Rev. Sci. Instrum. 57, 2101 (1986)] are simulated with three-dimensional HYDRA radiation hydrodynamics code [NTIS Document No. DE-96004569 (M. Marinak al. in UCRL-LR-105821-95-3)]. Simulations of ordered, near single mode perturbations indicate that structures which evolve into round spikes can penetrate farthest hot spot. Bubble-shaped burn through capsule shell fastest, case they cause even more damage. A...
Measurements are presented for the annihilation rates of thermalized positrons in a variety substances, including noble gases, simple inorganic molecules, hydrocarbons, substituted and aromatics. The measurements were performed using trapped clouds room-temperature positrons, into which substances under test introduced as low-pressure so that only two-body interactions involved. These data compared with other values literature, compilation is presented. measuremetns illustrate importance...
The neutron spectrum from a cryogenically layered deuterium–tritium (dt) implosion at the National Ignition Facility (NIF) provides essential information about performance. From measured primary-neutron (13–15 MeV), yield (Yn) and hot-spot ion temperature (Ti) are determined. scattered (10–12 MeV) relative to Yn, down-scatter ratio, fuel areal density (ρR) These parameters have been diagnosed an unprecedented accuracy with suite of neutron-time-of-flight spectrometers magnetic recoil...
Abstract The injection and mixing of contaminant mass into the fuel in inertial confinement fusion (ICF) implosions is a primary factor preventing ignition. ICF experiments have recently achieved an alpha-heating regime, which self-heating dominant source yield, by reducing susceptibility to instabilities that inject this mass. We report results unique separated reactants implosion studying pre-mixed as well detailed high-resolution three-dimensional simulations are good agreement with...
An indirectly-driven shock tube experiment fielded on the National Ignition Facility (NIF) was used to create a high-energy-density hydrodynamics platform at unprecedented scale. Scaling up shear-induced mixing previously OMEGA, NIF shear drives 130 μm/ns shocks into CH foam-filled (∼ 60 mg/cc) with interior dimensions of 1.5 mm diameter and 5 length. The pulse-shaping capabilities are extend drive for >10 ns, large volumes isolate physics-altering edge effects from region interest....
A series of high convergence, indirectly driven implosions has been done with the Nova Laser Fusion facility. These were well characterized by a variety measurements; computer models are in good agreement. The imploded fuel areal density was measured using technique based on secondary neutron spectroscopy. At capsule convergences 24:1, comparable to what is required for hot spot ignition scale capsules, these capsules achieved densities 19 g/${\mathrm{cm}}^{3}$. Independent measurements...
The lifetime of positrons confined in a Penning trap is studied the presence variety chemical species. large observed annihilation rates on these molecules provide evidence that positron-molecule attachment general phenomenon, and distinct trends are identified. For example, rate fluorocarbons as much 3 orders magnitude smaller than for analogous hydrocarbons. An empirical scaling dependence molecular ionization potential
A very large area (7.5 mm2) laser-driven x-ray backlighter, termed the Big Area BackLighter (BABL) has been developed for National Ignition Facility (NIF) to support high energy density experiments. The BABL provides an alternative Pinhole-Apertured point-projection Backlighting (PABL) a field of view. This bypasses challenges PABL in equatorial plane NIF target chamber where space is limited because unconverted laser light that threatens diagnostic aperture, backlighter foil, and pinhole...
Time-resolved drive measurements with thin-walled hohlraum targets on Omega [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)] are presented and compared two-dimensional hydrodynamical simulations. For the first time, radiation fluxes measured through laser entrance hole instead of a diagnostic side hole. We find improved agreement between time dependent experiments simulations using this new technique. In addition, history obtained in manner correlates well onto capsule at target center.
Understanding drive symmetry in gas-filled hohlraums is currently of interest because the baseline design indirect ignition target for planned National Ignition Facility uses a hohlraum. This paper reports on results series experiments performed at Nova laser [C. Bibeau et al. Appl. Opt. 31, 5799 (1992)] facility Lawrence Livermore Laboratory with goal understanding time-dependent gas filled hohlraums. Time-dependent data from capsule implosions and reemission targets are discussed. Results...
Mix of ablator material into fuel an ICF capsule adds non-burning material, diluting the and reducing burn. The amount reduction is dependent in part on morphology mix. A probability distribution function (PDF) burn model has been developed [6] that utilizes average concentration mixed materials as well variance this quantity across cells provided by BHR turbulent transport [3] its revisions [4] to describe mix terms a PDF concentrations provides rate material. Work underway develop MARBLE...
Using a large volume high-energy-density fluid shear experiment ($8.5\text{ }\text{ }{\mathrm{cm}}^{3}$) at the National Ignition Facility, we have demonstrated for first time ability to significantly alter evolution of supersonic sheared mixing layer by controlling initial conditions that layer. By altering surface roughness tracer foil, demonstrate transition from highly ordered system coherent structures randomly with faster growing mix layer, indicative strong in temperature several tens...
The MARBLE project is a novel inertial confinement fusion platform for studying the development of atomic mixing and temperature equilibration in implosions their impact on thermonuclear burn. Experiments involve laser-driven implosion capsules filled with deuterated engineered foams whose pores are gaseous mixture hydrogen tritium. By varying size foam pores, we can study timescale mix relative to thermal equilibrium between species. In contrast, previous separated reactant experiments have...