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.

Shock Initiation Microscopy with High Time and Space Resolution

“…The pyrometer was calibrated using a radiometric source (Ocean Optics HL-2000) coupled to a Labsphere, Inc. 2" diameter Spectraflect-coated uniform source, which produces a spatially-uniform output calibrated to a NIST-traceable source by Labsphere. Graybody methods for temperature fitting have been described previously [12,13]. Briefly, Planck's Law, Eq.…”

“…In the past several years, multiple research groups have developed tabletop shock generation systems to facilitate a greater understanding of the many facets of the complex phenomena involved in topics ranging from detonation propagation , to chemical reaction pathways under shock conditions , and hot spot temperature measurements . With the exception of the work of Tappan et al .…”

“…In the past several years, multiple research groups have developed tabletop shock generation systems to facilitate a greater understanding of the many facets of the complex phenomena involved in topics ranging from detonation propagation [6,7], to chemical reaction pathways under shock conditions [8][9][10][11], and hot spot temperature measurements [12,13]. With the exception of the work of Tappan et al on microenergetics, where research is conducted at the limit of failing detonation to gain insight into these fail-ure mechanisms [7,14], the sample dimensions in these experiments are below the dimension where traditional detonations can occur [15,16] because the diameter is below the critical diameter and the run distance is often less than the length of the reaction zone.…”

“…With the exception of the work of Tappan et al on microenergetics, where research is conducted at the limit of failing detonation to gain insight into these fail-ure mechanisms [7,14], the sample dimensions in these experiments are below the dimension where traditional detonations can occur [15,16] because the diameter is below the critical diameter and the run distance is often less than the length of the reaction zone. When such tiny samples are subjected to powerful shock waves, whether from a donor explosive [7], laser-driven impactor [12], or direct laserdrive [10], it is imperative to know the condition of the sample so that it can be related to both macroscale experiments and theoretical models. In the Dlott lab, laser-driven impactors drive short pulses (4-20 ns) into samples of liquid, particulate, single crystal or polymer-bound explosives (PBX), which are typically 1 mm in diameter and 40-500 μm thick.…”

Hot Spot Chemistry in Several Polymer‐Bound Explosives under Nanosecond Shock Conditions

“…Spectral radiance (i. e. the spectrally resolved emission) for a 2.8 km s −1 impact at various impact times is given in Figure for all formulations. X‐TATB shows strong deviations from graybody behavior ; however, the PETN, RDX, and TNT emission is well‐fit by the graybody model. The relative temperatures are seen from the spectral shape with X‐RDX being the hottest through this period and X‐TNT being the coolest.…”