DYNAMIC OBSERVATION OF A THERMALLY ACTIVATED STRUCTURE CHANGE IN 1,3,5-TRIAMINO-2,4,6-TRINITROBENZENE (TATB) BY SECOND HARMONIC GENERATION

Using optical second harmonic generation (SHG) we observe, for the first time, a structural change in the energetic material (dry-aminated production grade) TATB (1,3,5-triamino-2,4,6-trinitrobenzene) upon heating. This structure change is verified by X-ray powder diffraction (XPD). The kinetics of this structure change are measured and are found to closely match commonly accepted thermal decomposition parameters for the first step, analogous to observations made for the β to δ phase transition in HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Consequently, these solid structure transitions appear to be coupled to the chemical decomposition mechanism or it may be the first physical process occurring. We apply this technique as a diagnostic to an ignition experiment. This experiment demonstrates that the structure change can be rapid (it is thermally activated) and that SHG can be used to indicate not only the solid structure change (large increase in SHG intensity) but also the onset to significa...