Dynamic absorption in optical pyrometry of hot spots in plastic-bonded triaminotrinitrobenzene

Abstract

Herein, we demonstrate a methodology for performing optical pyrometry in environments which are disadvantageous for typical pyrometry applications by introducing additional fit parameters to account for absorption or emission which convolutes the thermal spectrum. Emission spectra from a plastic-bonded formulation of triaminotrinitrobenzene (TATB) shocked by 2-4 km s-1 impacts with Al flyer plates show significant deviations from graybody behavior. To extract reliable temperatures via optical pyrometry, we fit the spectra to a combination of a graybody and either a Gaussian absorption or emission spectrum. We found that the absorption needed to fit the data corresponds well to the known pressure-dependent absorption of TATB and that the absorption model gives temperatures and emissivities in line with other explosives. By contrast, assuming molecular emission gives temperatures too low and emissivities that decrease as more materials react. We conclude that the nonthermal part of the spectrum is dominated by the absorption of unreacted TATB and accurate pyrometry of TATB must either use our graybody plus absorption model or limit the spectral range of observation to above 650 nm.