Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session H1: Experimental Developments IV: X-ray I |
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Chair: Todd Hufnagel, Johns Hopkins University, Allen Dalton, Defense Threat Reduction Agency Room: Grand E |
Tuesday, June 16, 2015 9:15AM - 9:45AM |
H1.00001: Coherent X-ray Imaging Techniques for Shock Physics Invited Speaker: David Montgomery X-ray radiography has been used for several decades in dynamic experiments to measure material flow in extreme conditions via absorption of x-rays propagating through the materials. Image contrast in traditional radiography is determined by the absorption coefficients and areal densities of the materials at a given x-ray wavelength, and often limits these measurements to materials with sufficiently high atomic numbers and areal density, while low-Z materials and small areal density variations are completely transparent and not visible in the image. Coherent x-ray sources, such as those found at synchrotrons and x-ray free-electron lasers, provide new opportunities for imaging dynamic experiments due to their high spatial and spectral coherence, high brightness and short temporal duration ($<$ 100 ps). Phase-sensitive techniques, such as phase contrast imaging (PCI), rely on the overlap and interference of the x-rays due to spatial variations in their transmitted phase, and are enabled primarily by high spatial coherence of the x-ray source. Objects that are otherwise transparent to x-rays can be imaged with PCI, and small variations in areal density become visible that would be not observable with traditional radiography. In this talk an overview of PCI will be given, and current applications of this technique in high-energy density physics, shock physics and material dynamics will be presented. Other future uses of imaging using coherent x-ray sources in dynamic high-pressure experiments will be discussed. [Preview Abstract] |
Tuesday, June 16, 2015 9:45AM - 10:00AM |
H1.00002: Dynamic Multi-frame X-ray Phase Contrast Imaging of Impact Experiments at the Advanced Photon Source Brian Jensen, Anthony Fredenburg, Adam Iverson, Carl Carlson, Kamel Fezzaa, Bradford Clements, Mark Short Recent advances in coupling synchrotron X-ray diagnostics to dynamic compression experiments are providing new information about the response of materials at extremes conditions.~ For example, propagation based X-ray Phase Contrast Imaging (PCI) which is sensitive to differences in density (or index of refraction) has been successfully used to study a wide range of phenomena including jet-formation in metals, crack nucleation and propagation, and detonator dynamics.~ These experimental results have relied, in part, on the development of a robust, optically multiplexed detector system that captures single X-ray bunch images with micrometer spatial resolution on the nanosecond time scale.~~ In this work, the multi-frame PCI (MPCI) system is described along with experiments designed to examine the compression of an idealized system of spheres subjected to impact loading. Additional advances to the detector system will be presented that are designed to retrieve phase information from the X-ray images for fast tomography applications. Experimental results, implications, and future work will be discussed.~ [Preview Abstract] |
Tuesday, June 16, 2015 10:00AM - 10:15AM |
H1.00003: High-energy synchrotron X-ray radiography of shock-compressed materials Michael E. Rutherford, David J. Chapman, Mark A. Collinson, David R. Jones, Jasmina Music, Samuel J.P. Stafford, Gareth R. Tear, Thomas G. White, John B.R. Winters, Michael Drakopoulos, Daniel E. Eakins This presentation will discuss the development and application of a high-energy (50 to 250 keV) synchrotron X-ray imaging method to study shock-compressed, high-Z samples at Beamline I12 at the Diamond Light Source synchrotron (Rutherford-Appleton Laboratory, UK). Shock waves are driven into materials using a portable, single-stage gas gun designed by the Institute of Shock Physics. Following plate impact, material deformation is probed in-situ by white-beam X-ray radiography and complimentary velocimetry diagnostics [1]. The high energies, large beam size (13 x 13 mm), and appreciable sample volumes ($\sim$ 1 cm$^{3}$) viable for study at Beamline I12 compliment existing in-house pulsed X-ray capabilities and studies at the Dynamic Compression Sector. [1]: D. E. Eakins and D. J. Chapman, Review of Scientific Instruments 85, 123708 (2014). [Preview Abstract] |
Tuesday, June 16, 2015 10:15AM - 10:30AM |
H1.00004: Thin Object Radiography with a 2.2 MeV Pulsed Power Machine Todd Haines, Jeremy Danielson, W. Monty Wood An experimental series was performed at a pulsed-power 2.2 MeV flash radiography machine to determine the lower limits of its mass sensitivity. This machine uses a rod-pinch diode with accelerating potential of 2.2 MeV and 50 ns pulse duration. Tungsten, aluminum, and titanium rod anodes were used to tune the emitted bremsstrahlung spectrum; as well as aluminum and beryllium filter materials. Analysis of thin tantalum foils shows a mass sensitivity as low as 300 $\mu$g/cm$^2$. This is a factor of 5 better than previous measurements. [Preview Abstract] |
Tuesday, June 16, 2015 10:30AM - 10:45AM |
H1.00005: Development of Multi-GeV Electron Radiography for Measurements of Fast, Dynamic Systems Frank Merrill, Christopher Danly, Joseph Fabritius, Fesseha Mariam, Daniel Poulson, Raspberry Simpson, Peter Walstrom, Carl Wilde Charged particle radiography has been developed in the past decade to provide high-resolution, muti-frame flash radiography of dynamic systems. This development has focused on proton radiography utilizing 11 MeV to 50 GeV protons for a wide range of measurements. Recently, these techniques are being applied to the use of high energy electrons for applications at a future LANL MaRIE facility. At MaRIE Multi-GeV electrons will be used to diagnose small, quickly evolving systems, requiring resolution and frame rates beyond the capability of the existing 800 MeV proton radiography. The electron accelerator proposed for MaRIE will be capable of meeting the fast frame rate and resolution requirements for MaRIE. Because of the light mass of the electrons, bremsstrahlung processes become dominant in the electron interactions within the material being studied. Simulations have been performed to study these interactions, but measurements are required to fully understand the capabilities of this new measurement technique. A radiography system to make these measurements is being designed for measurements at the SLAC accelerator facility. We will present the plans for these measurements along with an estimate from simulations of the performance characteristics of a future capability. [Preview Abstract] |
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