Simultaneous Emission and Laser Absorption Spectroscopy Measurements in Post-Detonation Fireballs of Aluminized PETN Hemispheres

Laser absorption spectroscopy (LAS) and optical emission spectroscopy (OES) were used to characterize post-detonation fireballs of 12 mm hemispheres of pentaerythritol tetranitrate (PETN) with and without an aluminum shell. LAS was used to measure the temperature, pressure, and concentration of gaseous CO and CO2 at 0.5 or 1 MHz while OES was used to provide single-shot measurements of the temperatures of gaseous AlO and the condensed particulates as well as the ratio of Al and AlO concentrations. A quantum-cascade laser (QCL) emitting near 2008.5 cm^-1 was used to measure absorbance spectra of CO at 1 MHz, while an interband-cascade laser (ICL) emitting near 2394.75 cm^−1 was used to measure absorbance spectra of CO2 at 500 kHz. A broadband spectrometer was used to obtain measurements of emission spectra between 200 - 1100 nm with an integration time of 30 ����. The aluminum shell led to a significant (≈300-500 K) increase in the temperature of CO and the temperatures of AlO, and the particulates responsible for continuum emission were approximately 1000 K higher than that of CO, thereby indicating that the aluminum particles burned through diffusion flames. The measurements presented here demonstrate the potential for quantifying the impact of aluminum coatings upon the thermodynamic properties of post-detonation fireballs.