Infrared emissivity of tin upon release of a 25 GPa shock into a lithium fluoride window

Journal of Applied Physics

Asimow

Fat’yanov

et al. 2019

Self Cite

We have developed a new technique to measure the melt curve of a shocked metal sample and have used it to measure the high-pressure solid-liquid phase boundary of tin from 10 to 30 GPa and 1000 to 1800 K. Tin was shock compressed by plate impact using a single-stage powder gun, and we made accurate, time-resolved radiance, reflectance, and velocimetry measurements at the interface of the tin sample and a lithium fluoride window. From these measurements, we determined temperature and pressure at the interface vs time. We then converted these data to temperature vs pressure curves and plotted them on the tin phase diagram. The tin sample was initially shocked into the high-pressure solid γ phase, and a subsequent release wave originating from the back of the impactor lowered the pressure at the interface along a constant entropy path (release isentrope). When the release isentrope reaches the solid-liquid phase boundary, melt begins and the isentrope follows the phase boundary to low pressure. The onset of melt is identified by a significant change in the slope of the temperature-pressure release isentrope. Following the onset of melt, we obtain a continuous and highly accurate melt curve measurement. The technique allows a measurement along the melt curve with a single radiance and reflectance experiment. The measured temperature data are compared to the published equation of state calculations. Our data agree well with some but not all of the published melt curve calculations, demonstrating that this technique has sufficient accuracy to assess the validity of a given equation of state model.

Section: Resultsmentioning

confidence: 99%

High-pressure melt curve of shock-compressed tin measured using pyrometry and reflectance techniques

Journal of Applied Physics

Asimow

Fat’yanov

et al. 2019

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“…IS reflectometry is described in detail in [2], and reflectometry for a sample with a window is described in [3]. Our latest IS design has an internal xenon flash lamp (Tec/West U.S.A., model MFT-3222) operated at 320 V. The light from this lamp scatters in the IS many times to provide nearly 2 diffuse illumination of the sample.…”

Section: Methodsmentioning

confidence: 99%

“…In the past we observed reflectance changes from various metals shocked by high explosives and guns [1]; with the technology available at the time we saw indications of phase dependence. In a series of more recent publications [2][3][4] our group developed integrating sphere (IS) reflectance techniques to determine the emissivity and temperature of shocked tin in a region up to about 30 GPa, well above the tin -to-BCT (body-centered tetragonal) phase transition near 9 GPa [5]. Because the shock stress releases slowly due to Taylor wave release, we were also able to obtain estimates of the temperature versus stress [4].…”

Section: Introductionmentioning

confidence: 99%

Dynamic reflectance of tin shocked from its beta to BCT phase

Stevens

AIP Conference Proceedings

Turley

et al. 2017

Abstract. Shock-induced phase transitions have historically been inferred by features in loading/unloading velocity wave profiles, which arise due to volume or sound speed differences between phases. In 2010, we used a flash-lampilluminated multiband reflectometer to demonstrate that iron, tin, cerium, and gallium have measureable reflectance changes at phase boundaries. We have improved upon our prior technique, utilizing an integrating sphere with an internal xenon flash lamp to illuminate a shocked metal beneath a LiF window. The new reflectance system is insensitive to motion, tilt, or curvature and measures the absolute reflectance within five bands centered at 500, 700, 850, 1064, 1300, and 1550 nm. We have made dynamic reflectance measurements of tin samples shocked to pressures above and below the -BCT phase transition using a light gas gun. Below the transition, the visible reflectance decreases with pressure. At and above the transition, the visible reflectance increases to values higher than the ambient values. Reflectance can therefore be used to locate the -BCT phase transition boundary for tin, independent of the velocity wave profile. Using the reflectance data, we also present experimental estimates of the phase fraction as a function of shock stress.

“…Consequently, care must be taken to understand how the glue affects the thermal transport into the tin. The temperature of the shocked glue is estimated to be between 600 and 750 K, 26 and we have assumed that for these conditions the thermal conductivity of the glue remains small compared to that of the tin. This and similar glues are known to remain transparent at the stresses and temperatures in this work.…”

Section: A Pulsed Laser Heating Methodsmentioning

confidence: 99%

Thermal transport in shock wave–compressed solids using pulsed laser heating

Review of Scientific Instruments

Capelle

Stevens

et al. 2014

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Development of a simultaneous Hugoniot and temperature measurement for preheated-metal shock experiments: Melting temperatures of Ta at pressures of 100 GPa Review of Scientific Instruments 83, 053902 (2012); 10.1063/1.4716459 REVIEW OF SCIENTIFIC INSTRUMENTS 85, 073903 (2014) Thermal transport in shock wave-compressed solids using pulsed laser heating A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ∼25 GPa and ∼1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.