Quantum control of localized energy deposition into an energetic material is being investigated as a method to allow controlled initiation and propagation of action without transition to detonation. Quantum controlled initiation (QCI) of explosives utilize time dependent phase shaped ultraviolet (UV) electric fields to drive the energetic chemical systems towards reaction. QCI searches for an optimally shaped ultrafast laser pulse that will guide energy flow along a desired path. QCI can be exploited as a stand-off mitigation technology that strives to reduce the impact of explosive blasts on people and property by initiating controlled low order reaction. Quantum controlled initiation experiments require: (1) optimally shaped light pulses, (2) pulse shaping measurement, (3) feedback control algorithms, and (4) feedback measurement methods. Femtosecond laser pulse shaping in the UV at 400 nm employs a fused silica acousto-optic modulator (AOM) pulse shaper that consists of a 4-f zero dispersion compressor. Tr sient absorption spectroscopy is used to measure the pulse shaper effects. Both global and local optimization search routines such as genetic algorithm, differential evolution, and downhill simplex are used to search for the optimal pulse shape. Hexanitroazobenzene (HNAB), Trinitroanaline (TNA) and Diaminoazozyfurazan (DAAF) are excited to the first electronic state with 400 nm light. Our initiation experiments are studying the effect of phase shaped 400 nm pulses on HNAB, TNA and DAAF. The transient absorption spectra for each material have been obtained and note worthy regions further investigated with single parameter control (second order spectral phase and energy). Many systems have simple intensity control such as that shown by DAAF. TNA and HNAB have spectral features that are not single parameter driven and are being further investigated to obtain fully optimized complex control.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

DOE OSTI2010

Towards understanding initiation reactions of explosives via ultrafast laser quantum control

Optimal control can be utilized to control the initiation reaction of explosives, where time dependent phase shaped electric fields drive the chemical systems towards a desired state. For quantum controlled initiation (QCI) of explosives a pulse is created which seeks to achieve initiation by employing shaped ultraviolet light. QCI will enhance the understanding of energetic material reactions by yielding insight into the characteristics, such as critical 'hot spot' size and reaction dynamics, necessary for initiation. Quantum control experiments require the ability to: (1) phase and amplitude shape an ultrafast laser pulse, (2) measure the effect of pulse shape, and (3) optimize the desired outcome. Pulse shaping is performed with a 4-focal length dispersed fused silica acousto-optic modulator (AOM) at 400 nm in the ultraviolet (UV). Transient absorption spectroscopy is used to measure the pulse shape effects. Both global and local optimization search routines such as genetic algorithm, differential evolution, and downhill simplex are used to search for the optimal pulse shape. Hexanitroazobenzene (HNAB), Trinitroanaline (TNA) and Diaminoazozyfurazan (DAAF) are excited to the first electronic state with 400 nm light. Our initiation experiments are studying the effect of phase shaped 400 nm pulses on HNAB, TNA and DAAF. Novel transient absorption spectra for each material have been obtained and note worthy regions further investigated with single parameter control (second order spectral phase and energy). Many systems have simple intensity control such as that shown by DAAF. TNA and HNAB have spectral features that are not single parameter driven and are being further investigated with complex control.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗