Implementation of Single-Shot Ellipsometry on Gas Gun Experiments.
Abstract not provided.
Grant, Sean Campbell↗
Engineering topics
Ditmire, Todd
Publications and source records attributed to Ditmire, Todd.
Implementation of Single-Shot Ellipsometry on Gas Gun Experiments.
Abstract not provided.
Grant, Sean Campbell↗
Implementation of Single-Shot Ellipsometry on Gas Gun Experiments.
Abstract not provided.
Grant, Sean Campbell↗
Detection of Petawatt Laser-Induced Muon Source for Rapid High-Z Material Detection
A proof-of-concept investigation of a rapid detection system for shielded high-Z material using a petawatt laser-based muon source is presented. Unlike cosmic-ray muons, a laser-induced muon beam has unique characteristics that can be exploited for use in a rapid detection system. These characteristics include: (1) a near-point source of muons, (2) well-characterized muon energies, and (3) directionality of the beam. A detector system is being developed that combines multiple muon detection technologies to characterize an active muon source. This detection system and the associated data acquisition and analysis techniques are designed to search for deflections of the muon beam as it passes through high-Z materials. Additionally, the ability of the system to differentiate muons from the expected secondary particles, such as high-energy gammas and electrons, is being explored. The detector system’s ability to differentiate muons from other particles, show muon angular distribution, and measured muon flux will be discussed.
scintillation detector, petawatt laser-based muon ↗
The Texas petawatt laser and current experiments
The Texas Petawatt Laser is operational with experimental campaigns executed in both F/40 and F3 target chambers. Recent improvements have resulted in intensities of >2 Multiplication-Sign 10{sup 21} W/cm{sup 2} on target. Experimental highlights include, accelerated electron energies of >2 GeV, DD fusion ion temperatures >25 keV and isochorically heated solids to 10-50 eV.
43 PARTICLE ACCELERATORS↗
Magnetized and collimated millimeter scale plasma jets with astrophysical relevance
Magnetized collimated plasma jets are created in the laboratory to extend our understanding of plasma jet acceleration and collimation mechanisms with particular connection to astrophysical jets. In this study, plasma collimated jets are formed from supersonic unmagnetized flows, mimicking a stellar wind, subject to currents and magnetohydrodynamic forces. It is found that an external poloidal magnetic field, like the ones found anchored to accretion disks, is essential to stabilize the jets against current-driven instabilities. The maximum jet length before instabilities develop is proportional to the field strength and the length threshold agrees well with Kruskal-Shafranov theory. The plasma evolution is modeled qualitatively using MHD theory of current-carrying flux tubes showing that jet acceleration and collimation arise as a result of electromagnetic forces.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Modeling ramp compression experiments using large-scale molecular dynamics simulation.
Molecular dynamics simulation (MD) is an invaluable tool for studying problems sensitive to atomscale physics such as structural transitions, discontinuous interfaces, non-equilibrium dynamics, and elastic-plastic deformation. In order to apply this method to modeling of ramp-compression experiments, several challenges must be overcome: accuracy of interatomic potentials, length- and time-scales, and extraction of continuum quantities. We have completed a 3 year LDRD project with the goal of developing molecular dynamics simulation capabilities for modeling the response of materials to ramp compression. The techniques we have developed fall in to three categories (i) molecular dynamics methods (ii) interatomic potentials (iii) calculation of continuum variables. Highlights include the development of an accurate interatomic potential describing shock-melting of Beryllium, a scaling technique for modeling slow ramp compression experiments using fast ramp MD simulations, and a technique for extracting plastic strain from MD simulations. All of these methods have been implemented in Sandia's LAMMPS MD code, ensuring their widespread availability to dynamic materials research at Sandia and elsewhere.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗