Sensing inside explosions: Thermal history deduced from microparticle luminescence

Fires and explosions are some of the most difficult environments in which to perform sensing. A technology is reviewed that measures the temperature versus time relationship of such rapid thermal events. It utilizes the dependence of luminescence on the trap populations of dispersed micro- and nano-particles. The thermoluminescence (TL) of various oxide microparticles gives direct information on temperature and time because the trapped charges that ultimately give rise to TL have a probability of detrapping that follows an Arrhenius-type relationship. To test this concept, Mg₂SiO₄:Tb,Co particles with two thermoluminescent peaks have been heated using micromachined heaters over a 232°C to 313°C range on time scales of less than 200ms. The effect of maximum temperature during excitation on the intensity ratio of the two luminescent peaks has been compared with first-order kinetics theory and shown to match within an average error of 4.4%. Other TL particles have recently been tested and shown to survive Pentaerythritol Tetranitrate (PETN) explosions.