Engineering topics
Publications and source records attributed to Freeman, Richard.
Presentation to be presented during the Site-Directed Research and Development (SDRD) program FY 2021 review meeting (Webex), September 22–23, 2021.
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This document serves as the Final Technical Report for grant DE-SC0012333, The Measurement of Electrical and Thermal Conductivities in Warm Dense Matter . This work proposed to make the first systematic measurements of the reflectivity of warm dense matter (WDM) at multiple wavelengths by controlling and measuring the experimental factors necessary to use the reflectivity measurements to determine the electrical and thermal conductivity as a function of temperature and, to a lesser degree, density. A new technique was developed to measure the real and imaginary components of the electrical conductivity by making only scalar measurements of the relative reflectivity different angles. A series of preliminary experiments were designed to use the second, third, and fourth harmonics of the 800 nm driving laser. Reflectivity at each harmonic for two different angles would provide the scalar information needed to extract the real and imaginary parts of the index of refraction. Experiments were made using continuous wave lasers to determine the limits of accuracy on the measured reflectance for surrogate plane mirrors. It was determined, that while the technique was sound, the practical application of it was limited for the conditions on Scarlet. Due to significant challenges with the Scarlet Laser Facility at the time, progress was delayed.
We present proof-of-principle experimental results using a novel diagnostic designed to measure bulk fluid motion in materials. The diagnostic is based on quasi-monochromatic bent-crystal imaging in two narrow, closely-spaced wavelength bands within the spectral profile of the Co He-α line generated by laser irradiation of a solid Co target. Analysis of the two-dimensional (2D) maps obtained from the two crystals, coupled with spectroscopic measurements of the line width, allow a 2D ablation velocity map to be inferred. We describe the technique, the instrumentation, and the experiments we performed at the Z-Beamlet Laser Facility at Sandia National Laboratory, and we present the results and the analysis procedures we used to reconstruct a 2D velocity map. We also discuss possible extensions and improvements to the technique for future experimental applications.
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