This is an incomplete draft. Images have yet to be resized and will be on the large side for now. Apologies for the load times!
The inside of a high explosive detonation fireball is a place so violent, no contact sensor can brave the conditions within. If you want to know how hot it is, you have to measure it optically from a safe distance and hope you’re not blocked by debris, smoke, and other parts of the fireball.
We aim to change that.
Thermoluminescence (TL) is a phenomena found in certain materials which can trap charge carriers produced by ionizing radiation and store them until they are released by heat, whereupon they recombine and emit light. The TL project repurposes these materials–some new, some well-known for radiation dosimetry purposes–as incredibly tough, tiny, solid-state temperature sensors, irradiating TL particles before detonating them in explosives and reading out their remaining luminescence to reconstruct their ride.
|Irradiated TLD-200 chips being heated on a hotplate, displaying two distinct emissions peaks: one green…||…and one blue.|
|These particles are working micro-scale temperature sensors.||…and so, post-detonation and mixed with blast debris, are these.|
Of course, we wouldn’t be the Optical MEMS Group if we just stopped at microparticles. Tiny microscale electric heaters can heat and cool at speeds that are impossible for large hotplates, allowing us to subject the particles to explosion-like temperatures (okay, the mild ones) without actually blowing them up. (The administration gets very unhappy about too many explosions in the labs.)
Of course, explosions also involve violent accelerations and a good deal of strain on whatever is flying around in the vicinity. Large-area membranes–sheets of material hundreds of nanometers thick, yet centimeters on a side–allow us to stress a thermoluminescent film by electrically flexing its substrate.
Thin films capable of thermoluminescence were grown using electron-beam evaporation and characterized by identifying the crystalline structure and measuring the emission spectra.