Extending Optical Pyrometric Temperature Measurements to < 5000K

Measuring the temperature of dynamically compressed materials, especially quasi-isentropically compressed matter, is a grand challenge in high-energy-density physics. A streaked optical pyrometer, which simultaneously records the space- and time-resolved spectral radiance, is often used to determine the sample temperatures.[1] Typically, strong shock waves in initially transparent materials (i.e., quartz) at pressures of 100 GPa to several TPa are hot enough to emit enough photons to accurately measure the spectral radiance and infer the temperature. If the compressed sample is at a temperature below ~5000 K (Ref. [2]), however, low photon statistics combined with the amplification noise at the photocathode and the readout noise of the charge-coupled–device camera,[3] [JO1] make it difficult to determine the spectral radiance or temperature with traditional techniques. Here we describe a new statistical method that dramatically improves (reduces) this low-temperature limit for spectral radiance and temperature determination. Such data complement and help benchmark other techniques being developed to determine temperature of ramp-compressed materials such as extended x-ray absorption fine-structure (EXAFS) measurements.[4]

[1] M. C. Gregor et al., Rev. Sci. Instrum. 87, 114903 (2016).

[2] G. W. Collins et al., Phys. Rev. Lett. 87, 165504 (2001).

[3] S. Ghosh, R. Boni, and P. A. Jaanimagi, Rev. Sci. Instrum. 75, 3956 (2004).

[4] Y. Ping et al., Phys. Rev. Lett. 111, 065501 (2013).