Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session F1: Experimental Developments III: Energetic Materials II |
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Chair: Kevin McNesby, Army Research Laboratory, Joshua Felts, Naval Surface Warfare Center, Indian Head Room: Grand E |
Monday, June 15, 2015 5:00PM - 5:15PM |
F1.00001: Luminescent Sensors for Tracking Spatial Particle Distribution in an Explosion Hergen Eilers, Ray Gunawidjaja, Helena Diez-y-Riega, Forrest Svingala, Amber Daniels, James Lightstone We previously developed and tested thermally sensitive particles that, when seeded into an explosive event, flow with the expanding post-detonation fireball and provide ex-situ measurements of this thermal environment. This current work presents the development and testing of tracking particles that are used in concert with the thermally sensitive particles to encode the initial positions of materials recovered for ex-situ analysis. These tracking sensors consist of fully-crystallized (c) rare-earth-doped yttria particles such as c-Dy:Y$_{2}$O$_{3}$, c-Sm:Y$_{2}$O$_{3}$, and c-Er,Yb:Y$_{2}$O$_{3}$. The temperature sensors consist of mixtures of precursor (p) and fully crystallized materials such as p-Eu:Y$_{2}$O$_{3}$/c-Tb:Y$_{2}$O$_{3}$ or p-Eu:ZrO$_{2}$/c-Tb:Y$_{2}$O$_{3}$. Three mixtures containing one of the tracking sensors and one of the temperature sensing mixtures are placed at different locations within the chamber. Post-detonation, the tracking particles in the debris are excited by 365 nm light, resulting in different color luminescence, and allowing for potential visual inspection of the particle distribution originating from the different locations. Meanwhile, the temperature is determined from spectral changes of the precursor sensor materials or by comparison of the precursor sensor materials with the Tb:Y$_{2}$O$_{3}$ intensity reference. [Preview Abstract] |
Monday, June 15, 2015 5:15PM - 5:30PM |
F1.00002: Shock wave diagnostics using fluorescent dye probes Alexandr Banishev, James Christensen, Dana Dlott Fluorescent probes are highly developed, and have found increasing use in a wide variety of applications. We have studied shock compression of various materials with embedded dye probes used as high speed probes of pressure and temperature. Under the right conditions, dye emission can be used to make a map of the pressure distribution in shocked microstructured materials with high time (1 ns) and space (1 micrometer) resolution. In order to accomplish this goal, we started by studying shock compression of PMMA polymer with rhodamine 6G dye (R6G), as a function of shock pressure and shock duration. We observed the shock-induced spectral redshift and the shock-induced intensity loss. We investigated the fundamental mechanisms of R6G response to pressure. We showed that the time response of a dye probe is limited by its photophysical behavior under shock. We developed superemissive ultrafast dye probes by embedding R6G in a silica nanoparticle. More recently, we have searched for dye probes that have better responses. For instance, we have found that the dye Nile Red embedded in the right polymer matrix has 1.7 times larger pressure-induced redshift than R6G. [Preview Abstract] |
Monday, June 15, 2015 5:30PM - 5:45PM |
F1.00003: Fluorescence anisotropy measurements under shock compression Jue Wang, Will Bassett, Alexandr Banishev, Dana Dlott Fluorescence anisotropy measurements, where the parallel and perpendicular polarized emissions from probe molecules are acquired simultaneously, provide direct measurement of molecular rotational dynamics. In our experiments, the fluorescence from rhodamine 6G dye in various materials under GPa shocks produced by laser-driven flyer plates is collected, separated into two orthogonally-polarized beams using a Wollaston prism and detected with a streak camera. In liquids, the molecular rotations result from rotational diffusion and in solids from shear flow. The rotation rates can be used to determine the viscosity of the shocked medium. [Preview Abstract] |
Monday, June 15, 2015 5:45PM - 6:00PM |
F1.00004: Small-Scale Thermal Violence Cook Off Test Malcolm Cook, John Curtis, Christopher Stennett The Small-Scale thermal Violence Test (SSVT) is designed to quantify the violence (explosiveness) of test materials by means of observing the velocity history of a metal burst disk that forms one end of a strong thick-walled cylindrical test vehicle. A copper heating block is placed to the rear of, but in contact with, the sample and provides sealing. The difference in thermal conductivity between copper and steel is sufficient that thermal runaway is induced near to the explosive / copper interface in an unlagged test. A series of experiments has been made, in which explosive specimens were confined and heated to explosion. A high-accuracy velocity measurement system was used to record the motion of the bursting disk. These experiments have shown that the early-time motion of the bursting disk corresponds qualitatively to the onset of thermal explosion and growth of reaction within the explosive specimens. However, the velocity history traces are more complex than had been anticipated. In particular, unexplained shoulders were observed in the Phase-Doppler Velocimeter (PDV) data. Some preliminary modelling studies have been carried out in order to shed light on the complex shapes of the projectile velocity histories. [Preview Abstract] |
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