Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session C4: Experimental Developments II |
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Chair: Seth Root, Sandia National Laboratories Room: Renaissance Ballroom C |
Monday, June 27, 2011 11:00AM - 11:15AM |
C4.00001: Two-dimensional Imaging Velocity Interferometry: Technique and Data Analysis David Erskine, Ray Smith, Cindy Bolme, Peter Celliers, Gilbert Collins Velocity interferometers measuring target motion to high precision have been an important diagnostic in shockwave physics for many years. Until recently, this diagnostic has been limited to measuring motion at points or lines across a target. We describe an emerging interferometric technique for measuring motion across a two-dimensional image. Future advances in detector technology allows two-dimensional motion pictures, but the current implementation with integrating detectors uses pulsed illumination to freeze the target motion and return a velocity map at a specific moment in time. An ordinary image (lacking fringes) is also produced simultaneously. The preferred experimental arrangement includes a traditional line velocity interferometer measuring the same target, so that complementary records of velocity vs time and velocity vs x,y target position at a specific time are both measured. The 2-d interferometric technique, fringe analysis, and example data from recent experiments are described. [Preview Abstract] |
Monday, June 27, 2011 11:15AM - 11:30AM |
C4.00002: Laser Diagnostics for Simultaneous Measurements of Velocity and Concentration in Richtmyer-Meshkov Instabilities Ricardo Mejia-Alvarez, Katherine Prestridge Most experimental studies of RMI have not addressed the detailed structure of the unstable interface at different stages of its development. Rather, its spatial development has been typically restricted to thickness growth, and turbulence studies have been usually limited to pointwise measurements. To date, the only exception to this trend is simultaneous measurements of velocity and concentration via combined PIV and PLIF. Such work has been carried out by the Extreme Fluids Team at Los Alamos National Laboratory over a curtain of heavy gas with an initial varicose instability. Since no parallel of this work has been conducted on single interface configurations, the Team is currently developing a new Vertical Shock Tube (VST) to carry out such measurements. When completed, this facility will allow the simultaneous characterization of velocity and concentration fields at different stages of development of single-interface RMI flows, including turbulent regimes. Though the new VST is innovative in many regards (its shock wave is generated by a membraneless driver and its interface may be controllably perturbed), this talk will mainly focus on the characteristics, challenges, and range of possibilities of the laser diagnostics incorporated in the VST. [Preview Abstract] |
Monday, June 27, 2011 11:30AM - 11:45AM |
C4.00003: ABSTRACT WITHDRAWN |
Monday, June 27, 2011 11:45AM - 12:00PM |
C4.00004: An application of the emissive layer technique to temperature measurements by infrared optical pyrometer Camille Chauvin, Jacques Petit, Fr\'ed\'eric Sinatti A reliable measurement of the temperature of a material under dynamic loading is fundamental to differentiate its EOS. This aim is difficult to reach for temperatures lower than 1000 K due to the low amplitude of the radiated energy. A pyrometer has been developed at CEA Gramat to detect temperature from 373 K with a response time of 70 ns. An important parameter governing the material temperature estimation from the radiance measurements between the material and a LiF window is the evaluation of the dynamic emissivity. A way to overcome the lack of knowledge of emissivity consists in artificially increasing the emissivity of the material up to an apparent value of approximately 0.8 by the use of an emissive layer. The detected radiance is amplified and the range of dynamic emissivity is restricted. Promising results at material and LiF interface with an emissive layer of ReSi2 indicate that the mechanical, thermal and optical properties of this layer can be estimated and the sample temperature can be deduced. This paper investigates different parameters (roughness) potentially influencing the measured radiances at this complex interface. [Preview Abstract] |
Monday, June 27, 2011 12:00PM - 12:15PM |
C4.00005: Optical Properties measurements of Metals under shock compression using in-situ Ellipsometry Noaz Nissim, Lior Bakshi, Shalom Eliezer, Gabriel Applbaum, Lior Perelmutter, Michael Mond The study of the optical properties of materials at high pressure is a novel subject of research, and can be related to the knowledge of equation of state. The optical properties of materials are related to the electronic and structural properties of materials. Therefore, changes of the material optical properties can be used to detect phase transitions. The capability to measure optical properties and to detect phase transitions during a dynamic process is of great importance. Ellipsometry measures the change in the polarization of a probe beam reflected from a surface. From the change in polarization, the complex index of refraction can be extracted. Dynamic ellipsometry measurement system allows to measure all four stokes parameters and to derived the time dependent complex index of refraction. The dynamic ellipsometry was integrated with the gas gun facility for optical properties measurements under planer impact. The optical properties of 1020 steel and tin targets under different impact pressure were measured. The unique characteristics and changes of the optical properties of metals due to impact and heating experiments will be presented. [Preview Abstract] |
Monday, June 27, 2011 12:15PM - 12:30PM |
C4.00006: Embedded optical gauges for dynamic temperature measurements Daniel Dolan, Tom Ao While mechanical diagnostics are common in dynamic compression research, accurate temperature measurements remain elusive. The problem is particularly acute in ramp- compression experiments, where temperatures are often well below 1000 K, a challenging domain for optical pyrometry. Embedded electrical gauges can be used to measure temperature in limited circumstances, but are difficult to incorporate into metal samples or magnetically-driven experiments. Embedded optical gauges may provide a viable temperature diagnostic when pyrometry and electrical gauges are impractical. Unlike pyrometry, where each sample has a unique emissivity, embedded optical gauges reference temperature to the optical properties of a standard material. Active optical measurements also provide direct control over the measured light levels, whereas pyrometry is limited by sample emission in particular spectral regions. This presentation will discuss the use of noble metal reflectivity gauges for dynamic temperature measurements. [Preview Abstract] |
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