Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session Y3: AETD: Microscopy, emissivity, & reflectivity |
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Chair: Shawn McGrane, LANL Room: Pavilion East |
Friday, June 21, 2019 9:15AM - 9:30AM |
Y3.00001: Abstract Withdrawn
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Friday, June 21, 2019 9:30AM - 9:45AM |
Y3.00002: Shock compression microscopy: shocked materials with high time and space resolution Dana Dlott Our group has developed the ``shock compression microscope'' to study shocked solids and liquids with high time and space resolution. It consists of an inverted optical microscope, and a laser flyer plate launcher with a high-speed photon Doppler velocimeter. Flyer plates and samples are produced in the form of disposable arrays containing up to 200 individual samples. An array of optical diagnostics are used to measure pressure, density, temperature, composition and structure in real time. This general-purpose instrument launches flyer plates at 0-6 km/s, and the flyer plates produce reproducible flat and parallel impacts with a rise time of 0.5 ns. Shock durations can be varied from 2-20 ns. In this presentation, I will discuss the microscope and give an overview of some recent applications: shock initiation of plastic bonded explosives and real-time imaging of hot spots, shock-to-detonation on a tabletop where we study reproducible detonations, and shock compression of non-explosive materials including nanoparticle shock absorbers and biological systems. [Preview Abstract] |
Friday, June 21, 2019 9:45AM - 10:00AM |
Y3.00003: A Broadband Reflectance Diagnostic for Matter at Extreme Conditions Brian Henderson, Mohamed Zaghoo, Ryan Rygg, Danae Polsin, Tom Boehly, Gilbert Collins, Suzanne Ali, Peter Celliers, Amy Lazicki, Martin Gorman, Marius Millot, Richard Briggs, Jon Eggert, Malcolm McMahon In dynamic compression experiments, materials experience dramatic changes in their physical and chemical properties, manifesting in the material's optical properties. Reflectivity measurements are integral to detecting changes in chemical bonding and electronic structure for experiments involving high density and temperature. To this end, our work developed a normal-incidence, visible optical-reflectivity diagnostic for the OMEGA EP Laser System at the University of Rochester's Laboratory for Laser Energetics. This diagnostic measures the time- and wavelength-resolved reflectivity of laser-compressed materials. We present the design of the system, its performance, and experiments on compressed materials. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856, the University of Rochester, and the New York State Energy Research and Development Authority. [Preview Abstract] |
Friday, June 21, 2019 10:00AM - 10:15AM |
Y3.00004: Emissivity change in pressure-shear plate impact experiment Tong Jiao, Pinkesh Malhotra, Rodney Clifton Concurrent temperature measurement in a Pressure-Shear Plate Impact (PSPI) experiment has been developed by collecting the infrared radiation emitted from the sample/rear-plate interface. In order to convert the measured emittance to sample temperature accurately, the current emissivity of the sample/rear-plate interface is required. The initial emissivity is calibrated statically by comparing the collected emittance from the sample surface with that of a surface with known emissivity. In a PSPI experiment the effective emissivity may change due to inelastic deformation under pressure-shear loading. At thermodynamic equilibrium, the dynamic change of emissivity could be indicated through the change of reflectivity. Pilot experiments are conducted to gain a qualitative understanding of if and how the emissivity changes during a PSPI experiment. A Co$_{\mathrm{2}}$ laser is used to reflect an incident beam off the sample/rear-plate interface. The intensity of this reflected beam is monitored by a fast HgCdTe detector through a pair of 90$^{\mathrm{o}}$ off-axis parabolic reflectors. This measured change of intensity during a PSPI experiment provides an indication of the required change of emissivity. [Preview Abstract] |
Friday, June 21, 2019 10:15AM - 10:30AM |
Y3.00005: Refractive index measurements of atomic, molecular and mixed gases at high pressures up to 60 MPa Chengjun Li, Qifeng Chen, Yunjun Gu, Lei Liu, Guojun Li, Zhiguo Li The refractive index of initially transparent gases at high pressures is very important for shock velocity measurements in shock compression experiment since the measured shock velocity has to be modified by the refractivity of the initial sample. In this work, by using optical frequency domain interferometer (OFDI), we measured the refractive index of atomic (He, Ne, Ar, Kr, Xe), molecular (H$_{\mathrm{2}}$, D$_{\mathrm{2}}$, O$_{\mathrm{2}}$, N$_{\mathrm{2}})$ and mixed gases (H$_{\mathrm{2}}+$D$_{\mathrm{2}}$, H$_{\mathrm{2}}+$Ar, D$_{\mathrm{2}}+$He) up to 60 MPa. The polarizability of different gases were derived from their refractive index according to Lorentz-Lorenz formula. The measured equation of state (P-V-T) are also compared with the predictions of Self-consistent Fluid Variation Theory (SFVT) and other gaseous equation of state under the pressures interested. The mixing rule below 60 MPa were verified by the experimental results of mixed gases investigated in this work. [Preview Abstract] |
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