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 O1: Detonation and Shock-induced Chemistry V: Initiation Chemistry |
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Chair: Kathryn Brown, Los Alamos National Laboratory, Mario Fajardo, Air Force Research Laboratory, Eglin Room: Grand E |
Wednesday, June 17, 2015 9:15AM - 9:45AM |
O1.00001: Mechanisms of Shock-Induced Reactions in High Explosives Invited Speaker: Jeffrey Kay Understanding the mechanism by which shock waves initiate chemical reactions in explosives is key to understanding their unique and defining property: the ability to undergo rapid explosive decomposition in response to mechanical stimulus. Although shock-induced reactions in explosives have been studied experimentally and computationally for decades, the nature of even the first chemical reactions that occur in response to shock remain elusive. To predictively understand how explosives respond to shock, the detailed sequence of events that occurs - mechanical deformation, energy transfer, bond breakage, and first chemical reactions - must be understood at the quantum-mechanical level. This paper reviews recent and ongoing experimental and theoretical work in this important area of explosive science. [Preview Abstract] |
Wednesday, June 17, 2015 9:45AM - 10:00AM |
O1.00002: The Interaction of Explosively Generated Plasma with Explosives Douglas Tasker It has been shown that the temperature of explosively generated plasma (EGP) is of the order of 1 eV and plasma ejecta can be focused to achieve velocities as high as 25 km/s. These high velocity plasma can readily penetrate a wide range of materials including metals. Proof-of-principle tests were performed to determine if EGP could be used for explosive ordnance demolition and other applications. The test goals were: to benignly disable ordnance containing relatively sensitive high performance explosives (PBX-9501); and to investigate the possibility of interrupting an ongoing detonation in a powerful high explosive (again PBX-9501) with EGP. Experiments were performed to establish the optimum sizes of plasma generators for the benign deactivation of high explosives, i.e., the destruction of the ordnance without initiating a detonation or comparable violent event. These experiments were followed by attempts to interrupt an ongoing detonation by the destruction of the unreacted explosive in its path. The results were encouraging. First, it was demonstrated that high explosives could be destroyed without the initiation of a detonation or high order reaction. Second, ongoing detonations were successfully interrupted with EGP. LA-UR-15-20612. [Preview Abstract] |
Wednesday, June 17, 2015 10:00AM - 10:15AM |
O1.00003: Measurement of Carbon Condensates Using Small-Angle X-ray Scattering During Detonation of High Explosives Trevor Willey, M. Bagge-Hansen, L. Lauderbach, R. Hodgin, S. Bastea, L. Fried, A. Jones, D. Hansen, J. Benterou, C. May, T. van Buuren, T. Graber, B. Jensen, J. Ilavsky The lack of experimental validation for processes occurring at sub-micron length scales on time scales ranging from nanoseconds to microseconds hinders detonation model development. Particularly, quantification of late-time energy release requires measurement of carbon condensation kinetics behind detonation fronts. A new small-angle x-ray scattering (SAXS) end station has been developed for use at The Dynamic Compression Sector to observe carbon condensation during detonation. We started with hexanitrostilbene (HNS) due to its stability, ease of initiation, vacuum compatibility, and oxygen deficiency. The endstation and beamline demonstrate unprecedented fidelity; the first SAXS data contains a clear Guinier knee and power law slope, giving information about the size and morphology of the resultant carbon nanoparticles. HNS detonation produces particles with an Rg of 2.7 nm in less than 400 ns, and this size is constant over the next several microseconds. This result with HNS differs dramatically compared with previous pioneering work on RDX/TNT and TATB, where observations indicate significant particle growth (\textgreater 50{\%}) continues over several microseconds. The power-law slope is consistent with sp$^{\mathrm{2}}$ carbon. We have also begun to measure, and will present preliminary results on carbon condensates from Comp B, DNTF, and other explosives. [Preview Abstract] |
Wednesday, June 17, 2015 10:15AM - 10:30AM |
O1.00004: Single-shot Raman spectroscopy and time-resolved reflectivity of a shocked TATB-based explosive Philippe Hebert, Charles Saint-Amans, Michel Doucet, Thibaut de Resseguier Single-shot Raman spectroscopy experiments under shockwave loading were performed in order to get information on the initiation mechanisms that can lead to sustained detonation of a TATB-based explosive. Shocks up to 30~GPa were generated using a two-stage laser-driven flyer plate generator. The samples were confined by an optical window and shock pressure was maintained for at least 30~ns. Photon Doppler Velocimetry measurements were performed at the explosive/window interface to determine the shock pressure profile. Raman spectra were recorded as a function of shock pressure and the shifts of the principal modes were compared to static high-pressure measurements performed in a diamond anvil cell. Our shock data indicate the role of temperature effects on the H-bonding network present in TATB. Our Raman spectra also show a progressive extinction of the signal which disappears around 9~GPa. High-speed photography images reveal a simultaneous progressive darkening of the sample surface up to total opacity at 9~GPa. Time-resolved reflectivity measurements under shock compression seem to indicate that this opacity is due to a broadening of the absorption spectrum over the entire visible region. [Preview Abstract] |
Wednesday, June 17, 2015 10:30AM - 10:45AM |
O1.00005: Shock-driven chemistry and reactive wave dynamics in benzene Stephen Sheffield, Dana Dattelbaum, Joshua Coe Benzene is a stable organic chemistry molecule because of its electronic structure -- aromatic stability is derived from its delocalized, $\pi $-bonded, 6-membered planar ring structure. Benzene principal shock Hugoniot states have been reported previously by several groups, at both high and low pressures. Cusps (or discontinuities) in the shock Hugoniot provide evidence that chemical reactions take place under shockwave compression of benzene at input pressure conditions above 12 GPa. In other shock-driven experiments, spectral changes have been observed near this cusp condition, indicating that the cusp is associated with shock-driven chemical reaction(s). In this work, a series of gas-gun-driven plate impact experiments were performed to measure and quantify the details associated with shock-driven reactive flow in benzene. Using embedded electromagnetic gauges (with up to 10 Lagrangian gauge positions in-material in a single experiment) multiple, evolving wave structures have been measured in benzene when the inputs were above 12 GPa, with the details changing as the input pressure was increased. Detailed insights into the volume changes associated with the chemical reaction(s), reaction rates, and estimates of the bulk moduli of reaction intermediates and products were obtained. Using this new experimental data (along with the older experimental data from others), the benzene reactant and product Hugoniot loci have been modeled by thermodynamically complete equations of state. [Preview Abstract] |
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