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X-Ray Diffraction Measurements on Laser-Compressed Polycrystalline Samples Using a Short-Pulse Laser Generated X-Ray Source

Schollmeier, Marius; Ao, Tommy A.; Field, Ella S.; Galloway, B.R.; Laros, James H.; Kimmel, Mark W.; Long, Joel L.; Morgan, Dane V.; Rambo, Patrick K.; Schwarz, Jens S.; Seagle, Christopher T.

Existing models for most materials do not describe phase transformations and associated lattice dy- namics (kinetics) under extreme conditions of pressure and temperature. Dynamic x-ray diffraction (DXRD) allows material investigations in situ on an atomic scale due to the correlation between solid-state structures and their associated diffraction patterns. In this LDRD project we have devel- oped a nanosecond laser-compression and picosecond-to-nanosecond x-ray diffraction platform for dynamically-compressed material studies. A new target chamber in the Target Bay in building 983 was commissioned for the ns, kJ Z-Beamlet laser (ZBL) and the 0.1 ns, 250 J Z-Petawatt (ZPW) laser systems, which were used to create 8-16 keV plasma x-ray sources from thin metal foils. The 5 ns, 15 J Chaco laser system was converted to a high-energy laser shock driver to load material samples to GPa stresses. Since laser-to-x-ray energy conversion efficiency above 10 keV is low, we employed polycapillary x-ray lenses for a 100-fold fluence increase compared to a conventional pinhole aperture while simultaneously reducing the background significantly. Polycapillary lenses enabled diffraction measurements up to 16 keV with ZBL as well as diffraction experiments with ZPW. This x-ray diffraction platform supports experiments that are complementary to gas guns and the Z facility due to different strain rates. Ultimately, there is now a foundation to evaluate DXRD techniques and detectors in-house before transferring the technology to Z. This page intentionally left blank.

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TYPE SAND Report YEAR 2018
DOIOSTI

Shock-ramp compression of tin near the melt line

AIP Conference Proceedings

Seagle, Christopher T.; Porwitzky, Andrew J.

Tin has been shock compressed to ∼69 GPa on the Hugoniot using Sandia's Z Accelerator. A shockless compression wave closely followed the shock wave to ramp compress the shocked tin and probe a high temperature quasi-isentrope near the melt line. A new hybrid backwards integration - Lagrangian analysis routine was applied to the velocity waveforms to obtain the Lagrangian sound velocity of the tin as a function of particle velocity. Surprisingly, an elastic wave was observed on initial compression from the shock state. The presence of the elastic wave indicates tin possess a small but finite strength at this shock pressure, strongly indicating a (mostly) solid state. High fidelity shock Hugoniot measurements on tin sound velocities in this stress range may be required to refine the shock melting stress for pure tin.

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TYPE Journal Article YEAR 2018
DOIOSTIScopus

Enhanced dual confocal measurement system

Fusion Science and Technology

Seagle, Christopher T.; Tomlinson, K.; Huang, H.; Smith, G.E.; Taylor, J.L.; Paguio, R.R.

A measurement instrument utilizing dual, chromatic, confocal, distance sensors has been jointly developed by General Atomics and Sandia National Laboratories (SNL) for thickness and flatness measurement of target components used in dynamic materials properties (DMP) experiments on the SNL Z-Machine (Z). Compared to previous methods used in production of these types of targets, the tool saves time and yields a 4× reduction in thickness uncertainty which is one of the largest sources of error in equation of state measurements critical to supporting the National Nuclear Security Administration Stockpile Stewardship program and computer modeling of high energy density experiments. It has numerous differences from earlier instruments operating on the dual confocal sensor principle to accommodate DMP components including larger lateral travel, longer working distance, ability to measure flatness in addition to thickness, built-in thickness calibration standards for quickly checking calibration before and after each measurement, and streamlined operation. Thickness and flatness of 0.2- to 3.3-mm-thick sections of diamond-machined copper and aluminum can be measured to submicron accuracy. Sections up to 6 mm thick can be measured with as-yet undetermined accuracy. Samples must have one surface which is flat to within 300 µm, lateral dimensions of no more than 50 ×50 mm, and height less than 40 mm.

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TYPE Journal Article YEAR 2018
DOIOSTIScopus

Measurement of Body-Centered-Cubic Aluminum at 475 GPa

Physical Review Letters

Polsin, D.N.; Fratanduono, D.E.; Rygg, J.R.; Lazicki, A.; Smith, R.F.; Eggert, J.H.; Gregor, M.C.; Henderson, B.H.; Delettrez, J.A.; Kraus, R.G.; Celliers, P.M.; Coppari, F.; Swift, D.C.; McCoy, C.A.; Seagle, Christopher T.; Davis, Jean-Paul D.; Burns, S.J.; Collins, G.W.; Boehly, T.R.

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp-compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216±9 and 321±12 GPa, respectively, with the bcc phase persisting to 475 GPa. The high-pressure crystallographic texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

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TYPE Journal Article YEAR 2017
DOIOSTIDOIScopusOSTIScopus
Results 26–50 of 90
Results 26–50 of 90