Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session W1: DC-5: Ignition, Growth, Detonation |
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Chair: Bryan Henson, Los Alamos National Laboratory Room: Tennessee Ballroom C |
Thursday, July 2, 2009 3:30PM - 3:45PM |
W1.00001: Shock Wave-Induced Chemical Decomposition of RDX Crystals Zbigniew Dreger, James Patterson, Maosheng Miao, Yogendra Gupta Time-resolved optical spectroscopy and quantum chemistry calculations were combined to gain insight into molecular processes in shock-induced decomposition of RDX. Crystals of [111] orientation were shocked to peak stresses between 7.0 and 20.0 GPa. Broadband light emission was observed over the range of 350 - 850 nm with a threshold in spectral behavior at about 10 GPa. Below this threshold, the spectral profile remained unchanged during the experiment. Above 10 GPa, the emission spectrum changed with time and shifted to longer wavelengths. Based on these observations and quantum calculations, the emission spectrum was assigned to NO$_{2}$ radicals and HONO intermediates. Unimolecular decomposition of RDX leads to the production of these species through multiple decomposition steps. The observed threshold behavior is proposed to be due to the onset of bimolecular reactions between radical decomposition products and unreacted RDX molecules. We put forward a full decomposition scheme consistent with the main observations from our spectroscopy experiments. This work demonstrates the value of combining spectroscopy experiments with first principles calculations to understand decomposition of HE crystals. [Preview Abstract] |
Thursday, July 2, 2009 3:45PM - 4:00PM |
W1.00002: Development of the Small-Scale Shock Sensitivity Test (SSST) Joshua Felts, Harold Sandusky, Richard Granholm This effort is to develop a small-scale test to measure shock sensitivity that only needs a half gram sample at most. The test will screen new energetic compositions before the need for costly scale-up. The concept is to merge aspects of the Small-Scale Shock Reactivity Test (SSRT) developed at IHDIV, NSWC with that of gap tests. The SSRT measures the shock reactivity (explosiveness) of samples well-below critical diameter without requiring a transition to detonation. Gap tests are used to gage shock sensitivity of explosives, but require a sample size large enough for steady or near-steady detonation. The new test arrangement will combine the shock-attenuating gap before the sample and the air gap after the sample found in gap tests with the small sample size and high confinement of the SSRT. Our results for two plastic-bonded explosives formulated with either a regular or insensitive RDX confirm the difference in sensitivities observed in gap tests. More samples need to be tested to fully characterize the new test and to develop relations with shock sensitivity data from gap tests. [Preview Abstract] |
Thursday, July 2, 2009 4:00PM - 4:15PM |
W1.00003: Shock Reaction of Two Different RDX Fills in PBXN-109 Harold Sandusky, Joshua Felts, Richard Granholm Two types of Class 1 RDX from Dyno Nobel, one with reduced sensitivity and the other a Type II, were used in PBXN-109 gap tests. These tests include the large scale gap test (LSGT), the expanded large scale gap test (ELSGT), and a version of the ELSGT in which the acceptor is shortened to 102 mm and the witness plate is replaced with a block. In addition to the usual examination of the witness, instrumentation of acceptor tubes and fragment recovery were quite helpful in distinguishing between reaction levels. It was observed that low velocity detonation could steadily propagate the full length of the acceptor and punch a standard witness plate. At the critical gap, the accelerating growth of reaction that causes shock-to-detonation transition did not occur until near the witness end of the acceptor. These results will be related to a much smaller test with just 7.6-mm diameter samples from the same mixes, as described in another paper at this meeting. Discussion of reaction mechanisms will also include previously reported data from the modified gap test on a standard mix of PBXN-109. [Preview Abstract] |
Thursday, July 2, 2009 4:15PM - 4:30PM |
W1.00004: Proton Radiography of PBX 9502 Detonation Shock Dynamics Confinement Sandwich Test Tariq Aslam, Scott Jackson, John Morris Recent results utilizing proton radiography during the detonation of the high explosive PBX 9502 will be presented. Specifically, the effects of confinement of the detonation are examined in the LANL detonation confinement sandwich geometry. The resulting detonation velocity and detonation shock shape are measured. In addition, proton radiography allows one to image the reflected shocks through the detonation products. Comparisons are made with detonation shock dynamics and reactive flow models for the lead detonation shock and detonation velocity. In addition, predictions of reflected shocks are made with the reactive flow models. [Preview Abstract] |
Thursday, July 2, 2009 4:30PM - 4:45PM |
W1.00005: Confined PBX 9501 Gap Reinitiation Studies Terry Salyer For explosive systems that exhibit gaps or cracks between their internal components (either by design or mechanical failure), measureable time delays exist for detonation waves crossing them. Reinitiation across such gaps is dependent on the type of explosive, gap width, confinement, and temperature effects. To examine this reinitiation effect, a series of tests has been conducted to measure the time delay across a prescribed gap within an ``infinitely'' confined PBX 9501 system. Detonation breakout along the explosive surface is measured with a streak camera, and flow features are examined during reinitiation near the gap. Such tests allow for quantitative determination of the time delay corresponding to the time of initiation across a given gap oriented normal to the direction of the detonation wave. Measured time delays can be compared with established Pop plots and 1-D calculations, making it possible to estimate detonation run-up distances as well. These results are beneficial for the design and evaluation of explosive systems that require precision timing and performance. [Preview Abstract] |
Thursday, July 2, 2009 4:45PM - 5:00PM |
W1.00006: Modeling LX-17 Detonation Growth and Decay Using the Ignition and Growth Reactive Flow Model Craig Tarver, Steven Chidester The Ignition and Growth reactive flow model parameters for detonation waves in the TATB-based insensitive high explosive LX-17 are applied to two recent experiments. One experiment measures the slow increases in detonation velocity and pressure over several centimeters in confined charges as the steady state Chapman-Jouguet (C-J) values are approached. A second experiment measures the rate of detonation failure in an unconfined cylinder when the cylinder diameter is abruptly reduced. Good agreement is obtained between the measured and calculated detonation velocities and pressures for both experiments. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Thursday, July 2, 2009 5:00PM - 5:15PM |
W1.00007: Detonation Wave Profiles in Plastic Bonded Explosives Measured using 1550 nm Heterodyne Velocimetry Rick Gustavsen We have measured detonation wave profiles in several triaminotrinitrobenzene (TATB) and cyclotetramethylene tetranitramine (HMX or octogen) based plastic bonded explosives using 1550 nm Heterodyne Velocimetry. (Heterodyne Velocimetry is also called Photon Doppler Velocimetry or PDV.) Planar detonations were produced by impacting the explosive with projectiles launched in a gas gun. Particle velocity wave profiles were measured at the mirror/interface of the explosive and either a LiF or PMMA window. Mirrors consisted of either a thin vapor deposited aluminum layer, or a 6 micron thick aluminum foil. Focusing and collimating light collection probes were used. Time-Frequency-Analysis of the fringe data was carried out using both Wavelet and Short-Time-Fourier-Transform (STFT) methods. With clean fringe data, good profiles can be obtained with a 1 ns full width half maximum (FWHM) analysis window (STFT) or about 3 to 4 oscillations in the wavelet. Some profiles, however, have a noisy character which is correlated with intensity fluctuations in the raw fringe data. Wave profiles show a ZND reaction zone structure with a single reaction in the HMX based explosives and both fast and slow reactions in the TATB based explosives. [Preview Abstract] |
Thursday, July 2, 2009 5:15PM - 5:30PM |
W1.00008: Study of over compressed modes in detonation of condensed HE Alexey Fedorov, Anatoly Mikhailov, Dmitry Nazarov, Stanislav Finyushin, Tatiana Govorunova, Denis Kalashnikov, Evgeny Mikhailov We studied over compressed modes in detonation of condensed HE based on PETN, TNT and RDX using laser interferometer Fabry-Perot. We registered different profiles of detonation wave under different degrees of over compression: profiles in which the value of particle velocity either fell down after the shock-wave jump, or had a constant value, or smoothly grew up. Under maximum of over compression 2.4 times we registered increase in duration of chemical reaction (90 nsec) in compare with value of chemical spike (4 nsec) for stationary detonation wave. [Preview Abstract] |
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