Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session T4: NT.2 Novel Techniques: Velocity diagnostics |
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Chair: Scott Jackson, Los Alamos National Laboratory Room: Vashon |
Thursday, July 11, 2013 9:15AM - 9:30AM |
T4.00001: Measurement of an Explosively Driven Hemispherical Shell Using 96 Points of Optical Velocimetry Jeremy Danielson, Edward Daykin, Abel Diaz, Dean Doty, Brent Frogget, Mike Furlanetto, Cenobio Gallegos, Mike Gibo, Anselmo Garza, David Holtkamp, Mandy Hutchins, Candace Joggerst, Carlos Perez, Mike Pena, Vincent Romero, Mike Shinas, Matt Teel, Lenny Tabaka We report the measurement of the surface motion of a hemispherical copper shell driven by high explosives. This measurement was made using four 32 channel~multiplexed photonic Doppler velocimetry (PDV) systems, in combination with a novel compound optical probe. Clearly visible are detailed features of the motion of the shell over time, enhanced by spatial correlation. Significant non-normal motion is apparent, and challenges in measuring such a geometry are discussed. [Preview Abstract] |
Thursday, July 11, 2013 9:30AM - 9:45AM |
T4.00002: A multi-point radial photonic Doppler velocimetry (PDV) diagnostic for cylindrical implosion experiments Devon Dalton, Daniel Dolan, Raymond Lemke, Ryan McBride, Matthew Martin, Eric Harding, Scott Walker Radial photonic Doppler velocimetry (PDV) has been successfully applied in cylindrical implosion experiments fielded on Sandia's Z accelerator. Magnetically driven cylinders have been diagnosed well beyond 20 km/s, using a ``leapfrog'' configuration to address the bandwidth limitations of currently available detectors and digitizers. Implosion symmetry is the latest question this diagnostic will attempt to answer. An innovative multi-point configuration is being developed to allow six concurrent measurements during each experiment. This presentation describes the implementation of radial PDV in this extreme environment. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Dept. of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Thursday, July 11, 2013 9:45AM - 10:00AM |
T4.00003: Optical distance measurements to recover the material approach missed by optical velocimetry Matthew Briggs, Dan Knierim, Erik Moro, Shawn McGrane Optical velocimetry is limited to measuring the component of the target velocity along the axis of the optical beam, thereby allowing a laterally moving tilted surface to approach a probe undetected. In some applications it is important to know the distance to the target surface, and the forgoing means that integrating the velocity can give incorrect calculations of position. We will present three approaches to overcome this limitation: Tilted wavefront interferometry to map time of flight into fringe displacement; pulse bursts for which we measure the change in the average arrival time of a burst, and amplitude modulation interferometry in which a change in path length shows up as a change in the phase of the modulation. All three of these have the potential to be integrated with existing velocimetry probes for simultaneous velocity and displacement measurements. We will also report on initial tests of these approaches. LAUR - 13-21022 [Preview Abstract] |
Thursday, July 11, 2013 10:00AM - 10:15AM |
T4.00004: Optical pins for sub-nanosecond resolution of detonation break out Michael Shinas, Matthew Briggs, Michael Archuleta We report on the design and tests of optical pins that we have shown to resolve the arrival of a detonation front with a resolution of \textless 1ns. We coat the end of single-mode fiber with a 1000 {\AA}ngstr\"{o}m layer of aluminum and butt it against a detonator in various locations. Using an IR interferometer with the reference leg shifted in frequency (the type used for Photon Doppler Velocimetry), the disappearance of the fringes allows a measurement of the arrival of the detonation front to \textless 200 ps. The detonation arrival time measured with the optical pin and IR interferometer agree within the resolution of the measurement. A more field-able and affordable alternative using APDs \underline {A}valanche \underline {p}hoto\underline {d}iodes to measure the disappearance of the light reflected from the aluminum coating yields a resolution of 1ns. We present the design details and performance proof tests. LA-UR-13-21216 [Preview Abstract] |
Thursday, July 11, 2013 10:15AM - 10:30AM |
T4.00005: In-situ polymer strain diagnostics using mechanochemical sensor molecules Joseph Hooper, Patrick Smith, James Hemmer, Javier Read de Alaniz, Brian Mason, Joel Carney We report the synthesis and initial high-strain rate response of polymer materials with embedded force-sensitive molecules. PMA, PMMA, and HTPB were polymerized directly off a spiropyran molecule which undergoes a reversible ring-opening transition upon the application of local stress from the polymer chains. Following the transition there is a distinct change in color, UV response, and vibrational spectra as the spiropyran opens into a merocyanine form similar to many fluorescent dyes. In principle, these sensor molecules allow mapping of local strains with extremely high resolution and no perturbation of overall mechanical properties. However, this transition process has previously only been studied at very low quasistatic strain-rates, and was shown to be strongly affected by the nature of the polymer matrix, proximity to the glass transition, and other factors. We present the first dynamic loading experiments on these mechanochromic polymers using gas-gun and Hopkinson bar compression. Initial results on soft, elastomeric polymer matrices suggest widespread activation of the sensor molecule at high strain-rates, but that alternate synthesis and materials preparation strategies may be required to decouple the strain activation from straight thermal activation. [Preview Abstract] |
Thursday, July 11, 2013 10:30AM - 10:45AM |
T4.00006: Preliminary Investigations of HE Performance Characterization Using SWIFT Michael Murphy, Carl Johnson Initial pseudo-aquarium experimentation is underway to assess the utility of using the shock wave image framing technique (SWIFT) to characterize HE performance on detonator length and time scales. SWIFT is employed to directly visualize shock waves driven into polymethylmethacrylate (PMMA) samples through detonation interaction in pseudo-aquarium test geometries. Columns of XTX 8004, an extrudable RDX-based high explosive, are either cured directly within PMMA dynamic witness plates or within confinement tubes of different materials with varying shock impedances that are then embedded within PMMA. For current experiments, the SWIFT system records 16-frame image sequences using 175 ns inter-frame delays to directly visualize the evolution of lead shock-front geometries as they are driven radially into PMMA by the detonating XTX column. Standard aquarium-test analysis is employed to calculate shock pressure evolution within PMMA, and detonation wave velocities are accurately calculated from the time-resolved images as well. The SWIFT system and numerous pseudo-aquarium experimental results will be presented and discussed. [Preview Abstract] |
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