Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session C8: Spectroscopy and Optical Studies I |
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Chair: Brandon LaLone, NNSA Room: Grand Ballroom C |
Monday, July 10, 2017 11:15AM - 11:30AM |
C8.00001: Interaction of counter propagating laser induced shockwaves in atmospheric air Prem Kiran Paturi, Nagaraju Guthikonda, Leela Chelikani The spatio-temporal evolution of colliding ns laser induced shockwaves by varying the laser energy and the separation between the laser plasma sources (0.5 -- 10 mm) is presented. The input laser energy at one point is fixed to 25 mJ, whereas the other side is varied from 25 - 96 mJ. The plasma and shock wave interaction dynamics were observed to vary with varying energy deposition and distance between the two sources. The shock and contact fronts at the interaction zone between the two counter propagating LISW have showed interesting features. At initial time scales (\textasciitilde 1.6 \textmu sec) the plasma plumes have started interacting with each other that evolved into a stable bright interaction zone with increased intensity. Around 4 -- 8 \textmu sec two SW's are trying to propagate through each other resulting in quasi stable localized energy zone. At longer time scales \textgreater 20 \textmu sec, higher energy source propagates through the lower energy one leading to a discontinuity. These interaction dynamics are compared with the SWs from individual plasma sources to explicitly bring out the effect of interacting plasma sources on the SWs propagating into atmosphere. [Preview Abstract] |
Monday, July 10, 2017 11:30AM - 11:45AM |
C8.00002: A Study of Advanced Image Processing Techniques on Experimental SWIFT Data Christopher Trujillo Accurately tracking the position of explosive-induced shock waves is a critical method for characterizing high explosive (HE) performance. The application of the shock wave image framing technique (SWIFT) has proven to be a successful diagnostic tool that utilizes ultra-high-speed imaging to capture time series images of explosively-driven shock waves propagating through transparent media. The use of common edge-detection algorithms, including Sobel, Canny, and Prewitt, tend to be susceptible to background noise and require noise reduction preprocessing that can alter the position of edge boundaries. In this paper, results produced by the implementation of advanced image-processing techniques on experimental SWIFT data show that shock wave position can accurately be detected and tracked, while also maintaining robustness to background image noise. [Preview Abstract] |
Monday, July 10, 2017 11:45AM - 12:00PM |
C8.00003: Broadband laser ranging precision and accuracy experiments with PDV benchmarking Jared Catenacci, Ed Daykin, Marylesa Howard, Brandon LaLone, Kirk Miller Broadband laser ranging (BLR) is a developmental diagnostic designed to measure the precise position of surfaces and particle clouds moving at velocities of several kilometers per second. Recent single stage gas gun experiments were conducted to quantify the precision and accuracy possible with a typical BLR system. For these experiments, the position of a mirrored projectile is measured relative to the location of a stationary optical flat (uncoated window) mounted within the gun catch tank. Projectile velocity is constrained to one-dimensional motion within the gun barrel. A collimating probe is aligned to be orthogonal to both the target window and the mirrored impactor surface. The probe is used to simultaneously measure the position and velocity with a BLR and conventional Photonic Doppler Velocimetry (PDV) system. Since there is a negligible lateral component to the target velocity, coupled with strong signal returns from a mirrored surface, integrating the PDV measurement provides a high fidelity distance measurement reference to which the BLR measurement may be compared. [Preview Abstract] |
Monday, July 10, 2017 12:00PM - 12:15PM |
C8.00004: Dechirping analysis and calibration strategies for broadband laser ranging Marylesa Howard, Jared Catenacci, Michelle Rhodes, Natalie Kostinski, Adam Lodes The precise location of surfaces and ejected particulates is inferred through the fielding and analysis of broadband laser ranging. This developmental diagnostic complements its predecessor, photonic Doppler velocimetry, and is appropriate for surfaces moving many kilometers per second, including movement that is non-normal to the probe. Light from a pulsed femtoseconds laser is reflected from the target surface and mixed with light from a reference leg, which is then passed through dispersive fiber, resulting in chirped beat signals at the detector. Within the analysis, the dispersed laser pulses require temporal remapping due to the nonlinear optical dispersion of the fiber. Various approaches, including minimizing FFT peak widths and estimating phase, are discussed here, along with their respective merits. In addition, techniques for data calibration are presented, focusing on in-situ calibration for dynamic experiments and what to do when all else fails. [Preview Abstract] |
Monday, July 10, 2017 12:15PM - 12:45PM |
C8.00005: Two-dimensional imaging and velocimetry to diagnose heterogeneous deformation under dynamic compression Invited Speaker: Suzanne Ali As a material is dynamically compressed, heterogeneities form, perturbations propagate, and fracture networks develop. Information about the deformation and fracture of materials under shock compression is typically obtained in one of two ways; either derived post-shock, (i.e. from recovery experiments), where the material is shocked and then the recovered sample is examined, or inferred from features in one-dimensional transiting wave profiles. The first provides very limited information with regards to the time scale of deformation mechanisms, and the second provides limited information with regards to spatial scales. Recently, a two-dimensional imaging velocimetry technique has been developed on Omega (OHRV 2D-VISAR system) to measure the velocity roughness of shock fronts. We have used this diagnostic to study the heterogenous deformation in the elastic-plastic regime in diamond as well the propagation of perturbations in GDP, beryllium, and high density carbon ablators, observing features that are difficult to identify in one-dimensional experiments, but important for fully understanding dynamic material response. [Preview Abstract] |
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