Emissivity measurements of shocked tin using a multi-wavelength integrating sphere

Journal Article · Tue Nov 01 04:00:00 EDT 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3656429· OSTI ID:1055518

Seifter, A; Holtkamp, D B; Iverson, A J; Stevens, G D; Turley, W D; Veeser, L R; Wilke, M D; Young, J A

Pyrometric measurements of radiance to determine temperature have been performed on shock physics experiments for decades. However, multi-wavelength pyrometry schemes sometimes fail to provide credible temperatures in experiments, which incur unknown changes in sample emissivity, because an emissivity change also affects the spectral radiance. Hence, for shock physics experiments using pyrometry to measure temperatures, it is essential to determine the dynamic sample emissivity. The most robust way to determine the normal spectral emissivity is to measure the spectral normal-hemispherical reflectance using an integrating sphere. In this paper we describe a multi-wavelength (1.6–5.0 μm) integrating sphere system that utilizes a “reversed” scheme, which we use for shock physics experiments. The sample to be shocked is illuminated uniformly by scattering broadband light from inside a sphere onto the sample. A portion of the light reflected from the sample is detected at a point 12° from normal to the sample surface. For this experiment, we used the system to measure emissivity of shocked tin at four wavelengths for shock stress values between 17 and 33 GPa. The results indicate a large increase in effective emissivity upon shock release from tin when the shock is above 24–25 GPa, a shock stress that partially melts the sample. We also recorded an IR image of one of the shocked samples through the integrating sphere, and the emissivity inferred from the image agreed well with the integrating-sphere, pyrometer-detector data. Here, we discuss experimental data, uncertainties, and a data analysis process. We also describe unique emissivity-measurement problems arising from shock experiments and methods to overcome such problems.

• Research Organization: Nevada Test Site/National Security Technologies, LLC (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC52-06NA25946
• OSTI ID: 1055518
• Report Number(s): DOE/NV/25946--1239
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 9 Vol. 110
• Country of Publication: United States
• Language: English

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