Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session D4: Experimental Developments II |
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Chair: Jack Wise, Sandia National Laboratories Room: Fairmont Orchid Hotel Plaza II |
Monday, June 25, 2007 3:45PM - 4:00PM |
D4.00001: Dynamic reflectance measurements of shocked materials Daniel Dolan Temperature measurements are critical to equation of state development, but are notoriously difficult to perform and interpret. Infrared pyrometry is a valuable temperature diagnostic for a wide range of dynamic compression studies, but the technique is of limited use without knowledge of material emissivity. Although emissivity can be inferred from reflectance measurements---usually at ambient conditions---the manner in which this quantity changes with pressure, temperature, surface condition, and material phase is unknown. This presentation describes an emissivity characterization study of shock-compressed metal films. Real-time, infrared reflectance measurements are performed by coupling light from the VUV ring of the National Synchrotron Light Source to a gas gun system. As the samples are shock compressed, specular reflectance changes are measured using fast near- and mid-infrared detectors capable of tracking individual synchrotron pulses. This research provides data that can be used to constrain dynamic emissivity changes, and may lead to a set of emissivity standards that can be applied to any material. [Preview Abstract] |
Monday, June 25, 2007 4:00PM - 4:15PM |
D4.00002: ABSTRACT WITHDRAWN |
Monday, June 25, 2007 4:15PM - 4:30PM |
D4.00003: Using Schlieren Visualization to Track Detonator Performance Steven Clarke, Keith Thomas, Michael Martinez, Adrian Akinci, Michael Murphy, Ronald Adrian Several experiments that are part of a phased plan to understand the evolution of detonation in a detonator from initiation shock through run to detonation to full detonation to transition to booster and booster detonation will be presented. High Speed Laser Schlieren Movies have been used to study several explosive initiation events, such as exploding bridgewires (EBW), Exploding Foil Initiators (EFI) (or slappers), Direct Optical Initiation (DOI), and ElectroStatic Discharge (ESD). Additionally, a series of tests have been performed on ``cut-back'' detonators with varying initial pressing (IP) heights. We have also used this diagnostic to visualize a range of EBW, EFI, and DOI full-up detonators. Future applications to other explosive events such as boosters and IHE booster evaluation will be discussed. EPIC Hydrodynamic code has been used to analyze the shock fronts from the Schlieren images to reverse calculate likely boundary or initial conditions to determine the temporal-spatial pressure profile across the output face of the detonator. LA-UR-07-1229 [Preview Abstract] |
Monday, June 25, 2007 4:30PM - 4:45PM |
D4.00004: The use of silicone based adhesives to encapsulate manganin gauges for high stress experiments Ilan Be'ery, Zvi Rosenberg The use of commercial manganin stress gauges has been limited to stresses in the range of 0-20 GPa due to the short-circuiting of their encapsulating materials (epoxy, Kapton) at higher pressures. Researchers at Lawrence Livermore overcome this difficulty by embedding their gauges in Teflon sheets and measured shock pressures as high as 40 GPa. The fact that Teflon can keep its resistivity at high pressures is attributed to the lack of benzene rings in its structure. On the other hand, Teflon is difficult to work with as an encapsulating material because of its poor adhesive properties. In order to overcome this difficulty we encapsulated our foils in between two tapes of Teflon which have a silicone adhesive glued to it. These are 50 $\mu $m thick commercial tapes (manufactured by 3M, type {\#}60) which have a 50 $\mu $m thick silicone adhesive (PSA -- pressure sensitive adhesive) on them. This adhesive is easy to work with, has no benzene rings in its structure and has a lower carbon content, compared to other adhesives. Several experiments were conducted in order to directly measure the resistivity of these tapes at high pressures, as well as using them to encapsulate our manganin foils for high pressure studies. [Preview Abstract] |
Monday, June 25, 2007 4:45PM - 5:00PM |
D4.00005: The Dynamic Response of Piezoelectric Probes to Low Density Foam Impact Alan Mears, Frances Baily, Rebecca Strohmer Small lead zirconate titanate discs within commercial piezoelectric probes were impacted by low density foams in a set of gas gun experiments. For each probe the voltage across a 50 ohm load was measured to determine the change in electrical charge on the piezoelectric disc. Three different types of foam having densities between 0.1 and 0.35 g/cc were driven at velocities up to 1.0 km/s. Impact with the piezoelectric probes was calculated to generate stresses in the range 0.07 to 0.4 GPa. Hydrocode simulations were run to predict the stress history within the piezoelectric and to interpret the shape of the measured voltage pulse. From the experimental results the piezoelectric charge coefficient d33 was deduced to be around three times the low stress value available for the piezoelectric material. Results for an impact stress of 0.1 GPa followed by pressure release indicate that the dynamic change in polarization has a high degree of reversibility. [Preview Abstract] |
Monday, June 25, 2007 5:00PM - 5:15PM |
D4.00006: Magnetoelectric electrode gage - a technique for studying shock compression and matter metallization Sergey Gilev To study a material, which becomes conductive under compression, we use a new gage of mass velocity. Moving conductive matter generates emf at an electric circuit in transverse magnetic field. Voltage across the electrodes is determined by mean mass velocity at electromagnetic skin-layer in matter behind shock front. Layer thickness depends severely on the electric conductivity of shocked matter and is about 0.1-10 mm for materials investigated. A probing layer travels through the matter with shock velocity giving information on mass velocity under shock wave movement. Unlike the known techniques, the new instrument is Euler gage of mass velocity. Much electrode system allows one to obtain shock velocity at varied spatial bases. This technique is used to build Hugoniot of selenium and aluminum of different density. Experimental data are presented as dependencies of shock velocity on mass one. Thickness of probing layer for coarse powder is about shock transition thickness. This opens up possibilities using the technique for studying structure of shock transition and phase of matter metallization. [Preview Abstract] |
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