Diode laser gas sensing for high-speed temperature and speciation measurements inside explosive fireballs

There is a need for fundamental science to defeat weapons of mass destruction. Prompt bioagent defeat strategies invoke energetic materials to generate spore killing temperatures and halogen compounds. Developing predictive models for the bioneutralization efficiency of materials requires accurate experimental data to underpin the computational efforts. Certain thermodynamic parameters such as pressure are easily obtained in explosively driven flows. The temperature and chemistry of the interior of post-detonation fireballs is largely unmeasured at the current time. The present work was carried out in order to develop, demonstrate, and transfer technologies for making cost effective, high-speed, quantitative measurements of temperature and chemical speciation in near-field, post-detonation fireballs. This document presents the details of a hardened gauge that enables the fielding of a wide variety of proven tunable diode laser absorption techniques in explosive applications. In addition, details of the theory, application, and data analytics for the relevant spectroscopic measurements are also addressed. The developed hardware and technique were used to measure temperature at 30 kHz in chambered explosive fireballs by sweeping a tunable diode laser over a water vapor absorption band in the near infrared spectrum. Additional efforts were made to characterize the multiphase temperature of explosive fireballs. In addition to measuring temperature, a second tunable diode laser diagnostic was interfaced with the probe to measure atomic iodine in explosive fireballs as it is a halogen useful in agent defeat applications. Test data presented in this document were collected at a variety of scales ranging from milligrams of spark ignited thermites in a 2-liter chamber, to 10s of grams of aluminized, plastic explosives in an 1800-liter chamber. All data validate the ability of the combined probe and data analytics to survive the implicitly destructive intensity of explosive detonation and make high-speed optical measurements of temperature and atomic iodine concentration inside explosive fireballs