Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session D3: AETD: Detonation Diagnostics 1 |
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Chair: Arnaud Sollier, CEA Room: Pavilion East |
Monday, June 17, 2019 2:00PM - 2:30PM |
D3.00001: Pulsed Laser Imaging For Explosive Event Invited Speaker: Kevin McNesby Pulsed-laser, camera-synchronized shadowgraph imaging of bright events, such as following detonations of solid chemical explosives, is a useful method for imaging near-field phenomena close to the explosive center of mass. The intensity of pulsed laser light over a narrow wavelength range (typically near 0.001 nanometer (nm)) and pulse time duration (typically less than 30 nanoseconds (ns)) often equals or exceeds the brightness of the explosive event, allowing imaging of features normally obscured (e.g., shock separation from detonation products). For best image quality, laser coherence should be ``spoiled'' to minimize laser speckle, and the laser should be able to run continuously to enable capture of the full explosive event (often several milliseconds). Commercial high repetition rate (up to 3 megaHertz (MHz)), high power (up to 100 W average power), narrow linewidth (less than 0.03 nm at 532 nm) pulsed lasers capable of continuous operation are available. We examine two systems employing diode-pumped solid state (DPSS, Coherent Inc. Avia 532-65) and hybrid fiber-DPSS (Spectra-Physics Quasar 532-95) techniques. We have been investigating using these systems in laser shadowgraphy imaging systems, as an enhancement of our previous capabilities (20 kHz, 20W, Cu-vapor laser). Both of these laser systems exhibit laser speckle when the output beam is used to illuminate a surface. To minimize speckle, we use transfer optics employing a combination of liquid-filled light pipes and optical fibers. The use of the light pipe/optical fiber combination slightly broadens the laser line width while causing dispersion to the pulse, and provides an image speckle contrast ratio nearest (but not equal) to that obtained using an arc lamp. Preliminary results show that the combination of liquid filled light pipes and optical fibers can reduce speckle to obtain speckle contrast ratios approaching those obtained using incoherent light sources. The presentation will discuss Edgerton shadowgraphy using pulsed laser illumination, light pipes filled with different media, and discuss applications to medium scale energetic material testing now underway using these systems. [Preview Abstract] |
Monday, June 17, 2019 2:30PM - 2:45PM |
D3.00002: Quantitative High Speed Imaging for a Sympathetic Detonation Study Dana Duke, Amy Bauer, Jeremy Danielson, Robert Gonzales, David Oschwald An experiment was performed which tested the sympathetic detonation of a plastic encased cylinder of high explosive (HE) charge by an identical neighbor placed \textasciitilde 6cm away. The two cylindrical charges consisted of a plane wave lens in a delrin case, driven by an RP-1 detonator. A high speed Shimadzu HPV-X camera was focused on the packages to record 128 images, backlit with a magnesium bulb. In this work, we developed a quantitative analysis technique for high speed video footage of HE drives to verify sympathetic detonation. We measure the position of the expanding cases and record this position as a function of time. In the experiment, we first performed three separate measurements of single experimental charges. Comparisons were made between: a single HE charge, an HE charge impacting on a ``dummy'' plastic charge, and an HE charge on an HE charge. The disassembly speeds of the ``dummy'' and the ``live'' charges were compared and exhibited sympathetic detonation. In this talk, the high speed images will be shown and the analysis technique demonstrated. LA-UR-19-21554 [Preview Abstract] |
Monday, June 17, 2019 2:45PM - 3:00PM |
D3.00003: Developments and analysis of pulse correlation reflectometry for the characterisation of shock and detonation waves Callum Pryer Pulse Correlation Reflectometry (PCR) is a simple and robust new technique to measure the position of shock and detonation waves in a quasi-continuous manner by measuring the transit time of an electrical pulse in a coaxial electrical sensor. Experiments were performed to test the performance of different coaxial sensors with diameters from 0.36 mm up to 2.8 mm with a range of pulse repetition rates from 27 MHz to 71 MHz. The experiments were performed using a trackplate with the PCR sensors in contact with the explosive. Piezo pins were fielded to validate the measurements made. The data shows the thin coaxial cables perform well, with the velocity of detonation within 2 {\%} of those obtained from piezo pins. A new approach to the analysis was developed which allows the frequency of pulses to be increased, thereby increasing the number of datapoints. This high frequency analysis has been validated with both synthetic data and experimental data which produces velocity of detonation results that fit within errors of data captured using lower frequencies. \copyright British Crown Owned Copyright 2019/AWE [Preview Abstract] |
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