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 H4: Experimental Developments III |
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Chair: Brian Jensen, Sandia National Laboratories Room: Fairmont Orchid Hotel Plaza II |
Tuesday, June 26, 2007 1:45PM - 2:00PM |
H4.00001: New Capabilities of 800 MeV Proton Radiography at Los Alamos Cynthia Schwartz Three new capabilities have recently been commissioned at the proton radiography facility at Los Alamos. A powder gun driver system has been installed and commissioned and a series of demonstration measurements have been completed. This powder gun is now regularly used to drive dynamic experiments. A new CMOS hybrid camera technology has been developed and fielded resulting in dramatic improvements in quantum efficiency as well as providing eight additional radiographic images per dynamic event. A proton x3 magnifier was designed, built and commissioned to provide improved radiographic resolution for 800 MeV proton radiography experiments. Details of these new capabilities will be presented along with data from recent experiments which utilized these new capabilities. [Preview Abstract] |
Tuesday, June 26, 2007 2:00PM - 2:15PM |
H4.00002: Proton Radiography of a Thermal Explosion in PBX 9501 Laura Smilowitz, Bryan Henson, Jerry Romero, Blaine Asay, Mary Sandstrom The understanding of thermal explosions and burn propagation lags that of detonations and shock propagation. Diagnostics such as high energy radiography have been used to image shocks, but have been previously precluded from use in thermal explosions due to their stringent timing requirements: shock propagation can be synchronized to an external diagnostic while thermal explosion can not. This issue is solved by following the evolution of the ignition volume in a thermal explosion and using a laser pulse to provide a temperature jump in that central volume during the final thermal runaway leading to ignition. Details of the laser heating which minimize the perturbation of the thermal explosion will be discussed with comparisons between auto-ignited and laser ignited tests. Thermal explosion experiments have been conducted at the Los Alamos Proton Radiography facility and have yielded images of the evolution of ignition, post-ignition burn propagation, and case failure in a radially confined cylinder of PBX 9501. [Preview Abstract] |
Tuesday, June 26, 2007 2:15PM - 2:45PM |
H4.00003: Direct Shock-Density Measurements using Plate Impact and Proton Radiography Invited Speaker: Proton radiography (pRad) is a powerful new diagnostic with the potential of producing accurate (1\%) direct density measurements from dynamically loaded materials. Experiments have been performed to investigate the feasibility of using proton radiography (pRad) to obtain dynamic radiographs of shock-compressed materials during plate impact experiments. This work has involved the design, manufacturing, and testing of a new 40mm single-stage, powder driven gun, the development of methods to synchronize the shock event generated with the gun to proton output, and initial proof-of-principle experiments in Area C at LANSCE. To date, four symmetric impact experiments on aluminum and copper have been performed with successful synchronization. The method used to attain synchronization of the shock event to proton beam output will be discussed and the results of our initial experiments will be presented. [Preview Abstract] |
Tuesday, June 26, 2007 2:45PM - 3:00PM |
H4.00004: Neutron Resonance Spectrometry Shock Temperatures in Molybdenum Damian Swift, Achim Seifter, David Holtkamp, Vincent Yuan, David Clark, William Buttler Neutron resonance spectrometry (NRS) has been used to measure the temperature in Mo during shock loading, giving temperatures higher than expected. The effect of plastic flow and non-ideal projectile behavior were assessed. Plastic flow was estimated to contribute a temperature rise of 55K compared with hydrodynamic flow, and 100-150K on release, consistent with pyrometry measurements. Simulations were performed of the HE flyer system used to induce the shock in the Mo sample. The simulations predicted that the flyer was slightly curved on impact. The resulting spatial variations in load, including radial components of velocity, were predicted to increase the apparent NRS temperature by 160K. These corrections are sufficient to reconcile the apparent temperatures deduced using NRS with the accepted properties of Mo. [Preview Abstract] |
Tuesday, June 26, 2007 3:00PM - 3:15PM |
H4.00005: Detonation Shock Radius Experiments. David Lambert, Joshua Debes, Scott Stewart, Sunhee Yoo A previous passover experiment [1] was designed to create a complex detonation transient used in validating a reduced, asymptotically derived description of detonation shock dynamics (DSD). An underlying question remained on determining the location of the initial detonation shock radius to start the DSD simulation with respect to the dynamical response of the initiation system coupling's to the main charge. This paper concentrates on determining the initial shock radius required of such DSD governed problems. `Cut-back' experiments of PBX-9501 were conducted using an initiation system that sought to optimize the transferred detonation to the desired constant radius, hemispherical shape. Streak camera techniques captured the breakout on three of the prism's surfaces for time-of-arrival data. The paper includes comparisons to simulations using constant volume explosion and high pressure hot spots. The results of the experiments and simulation efforts provide fundamental design considerations for actual explosive systems and verify necessary conditions from which the asymptotic theory of DSD may apply. [1] Lambert, D., Stewart, D. Scott and Yoo, S. and Wescott, B., ``Experimental Validation of Detonation Shock Dynamics in Condensed Explosives\textit{. J. of Fluid Mechs., }Vol. 546, pp.227-253 (2006). [Preview Abstract] |
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