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 J2: Experimental Developments III: Detonators |
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Chair: Arianna Gleason, Los Alamos National Laboratory/SLAC Room: Grand Ballroom AB |
Tuesday, July 11, 2017 11:15AM - 11:30AM |
J2.00001: Dynamic Initiator Imaging at the Advanced Photon Source: Understanding the early stages of initiator function and subsequent explosive interactions. Nate Sanchez, Will Neal, Brian Jensen, John Gibson, Mike Martinez, Dennis Jaramillo, Adam Iverson, Carl Carlson Recent advances in diagnostics coupled with synchrotron sources have allowed the in-situ investigation of exploding foil initiators (EFI) during flight. We present the first images of EFIs during flight utilizing x-ray phase contrast imaging at the Advanced Photon Source (APS) located in Argonne National Laboratory. These images have provided the DOE/DoD community with unprecedented images resolving details on the micron scale of the flyer formation, plasma instabilities and in flight characteristics along with the subsequent interaction with high explosives on the nanosecond time scale. Phase contrast imaging has allowed the ability to make dynamic measurements on the length and time scale necessary to resolve initiator function and provide insight to key design parameters. These efforts have also probed the fundamental physics at ``burst'' to better understand what burst means in a physical sense, rather than the traditional understanding of burst as a peak in voltage and increase in resistance. This fundamental understanding has led to increased knowledge on the mechanisms of burst and has allowed us to improve our predictive capability through magnetohydrodnamic modeling. Results will be presented from several EFI designs along with a look to the future for upcoming work. [Preview Abstract] |
Tuesday, July 11, 2017 11:30AM - 11:45AM |
J2.00002: Rogowski coils for studies of detonator initiation Douglas Tasker The Rogowski coil dates back to 1887 and it has commonly been employed to measure rapid changes of electrical currents without direct contact with the circuits, especially in high energy density applications. Recently, it has been used to measure currents in relatively low energy devices such as semiconductor circuits; here we report its utility in the analysis of detonator initiation. From an electrical perspective, the coil is essentially an air-cored transformer and measures the temporal rate of change of current \textit{dI/dt}. Following a careful characterization of the circuit, an accurate measurement of this derivative is shown to provide a complete solution of the detonator circuit, including current, voltage, power and energy delivered to the detonator. The dependence of the electrical sensitivity, accuracy and bandwidth on coil design will be discussed and a new printed circuit design will be presented. Interesting features in the initiation of exploding bridgewire detonators have been observed with this coil and the results of various experiments will be discussed. [Preview Abstract] |
Tuesday, July 11, 2017 11:45AM - 12:00PM |
J2.00003: Assessing Detonator Health Using Rogowski Coil Data Peter Schulze, Ty Brooks, Doug Tasker, Matt Biss, Daniel Preston The Rogowski coil is commonly employed to measure rapid changes of electrical currents, especially in high power applications. Here we report the use of the coil to reveal subtle details of exploding bridgewire (EBW) detonator initiation and how the initiation is affected by aging.~ Detonator accelerated aging studies are aimed at understanding aging mechanisms and enabling predictive capabilities for aging. Rogowski Coil data from detonator accelerated aging studies offer a wealth of information regarding the electrical health of detonator, which is an important and complementary part of a comprehensive accelerated aging study. Herein we present the results of a variety of accelerated aging tests in detonators (thermal cycling, low power current damage, etc.) and the results that the Rogowski Coil affords us and how they inform us about the condition of the detonator. [Preview Abstract] |
Tuesday, July 11, 2017 12:00PM - 12:15PM |
J2.00004: Qualification of a multi-diagnostic detonator-output characterization procedure utilizing PMMA witness blocks Matthew Biss, Michael Murphy, Mark Lieber Experiments were conducted in an effort to qualify a multi-diagnostic characterization procedure for the performance output of a detonator when fired into a poly(methyl methacrylate) (PMMA) witness block. A suite of optical diagnostics were utilized in combination to both bound the shock wave interaction state at the detonator/PMMA interface and characterize the nature of the shock wave decay in PMMA. The diagnostics included the Shock Wave Image Framing Technique (SWIFT), a photocathode tube streak camera, and photonic Doppler velocimetry (PDV). High-precision, optically clear witness blocks permitted dynamic flow visualization of the shock wave in PMMA via focused shadowgraphy. SWIFT- and streak-imaging diagnostics captured the spatiotemporally evolving shock wave, providing a two-dimensional temporally discrete image set and a one-dimensional temporally continuous image, respectively. PDV provided the temporal velocity history of the detonator output along the detonator axis. Through combination of the results obtained, a bound was able to be placed on the interface condition and a more-physical profile representing the shock wave decay in PMMA for an exploding-bridgewire detonator was achieved. [Preview Abstract] |
Tuesday, July 11, 2017 12:15PM - 12:30PM |
J2.00005: Novel measurements of shock pressure decay in PMMA using detonator loading Michael Murphy, Mark Lieber, Matthew Biss An empirical model equation for shock pressure decay in PMMA was determined through a unique set of experiments employing detonator loading. Custom polymethyl methacrylate (PMMA) witness blocks were designed with monolithic architecture to house precise PMMA gap thicknesses ranging from 0-10 mm in 1 mm increments. The PMMA gaps separated detonator working surfaces from windowed photonic Doppler velocimetry (PDV) probes, and were designed to provide undistorted optical access to ultra-high-speed framing and digital streak cameras. The shock wave image framing technique (SWIFT), and a new laser-backlit digital streak diagnostic, simultaneously captured the temporal evolution of detonator-induced diverging shock waves within the PMMA gaps. The PDV diagnostic measured critical mass velocity histories as the shocks exited the variable gap thicknesses. The multi-diagnostic data package was used to characterize the shock pressure decay in PMMA as a function of shock propagation time and PMMA thickness. [Preview Abstract] |
Tuesday, July 11, 2017 12:30PM - 12:45PM |
J2.00006: On a physics-based model equation for shock-position evolution in PMMA Mark Lieber, Michael Murphy, Matthew Biss A governing differential equation for shock position in PMMA was derived from momentum conservation and an assumed exponential decay law for shock pressure. A new multi-diagnostic characterization method for measuring detonator output in PMMA witness blocks provided temporally-resolved, 1-D, shock-position data that was iteratively fit by solutions to the governing equation via a unique genetic algorithm solver. The goal was to calculate a solution that describes the temporal evolution of shock pressure in PMMA starting at the detonator interface. The exponential decay law was under investigation using experimental data, where different regimes were being considered for the decay coefficient. A successful solution provides extensive performance information that is directly relevant to the understanding and characterization of detonator function. [Preview Abstract] |
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