Probing aluminum reaction in high explosives via benchtop dynamic x-ray diffraction
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Brown, Cameron↗
Engineering topics
Smilowitz, Laura Beth
Publications and source records attributed to Smilowitz, Laura Beth.
Evaluation of silicon and indium gallium arsenide photodiodes as direct timing detectors for pulsed x-ray systems
Benchtop pulsed x-ray systems are commonly used to record dynamic material data on the order of nanoseconds, but pulse timing is often difficult to accurately determine. This study demonstrates that commercially available photodiodes can be used effectively for direct x-ray pulse detection without the need for visible light scintillators. X-ray pulses from four commercially available flash x-ray systems were quantified using one silicon and two indium gallium arsenide (InGaAs) photodiodes. The measured InGaAs pulse durations were strongly dependent on radiation dose in the non-linear operating regime, so the photodiodes were shielded to operate below the 2.5 V non-linear regime threshold. The average pulse duration and pulse arrival time jitter of the photodiodes for each x-ray source were within several nanoseconds with the exception of two sets of measurements that were affected by low instrument sensitivity and electrical noise. These results show that InGaAs photodiodes can be used as effective and repeatable stand-alone timing diagnostics for x-ray pulses as short as 20 ns or less.
47 OTHER INSTRUMENTATION↗
Time-resolved Flash X-ray Diffraction of Aluminized High Explosives [Slides]
Al HE generally has lower performance in Detonation Driving Zone but higher overall blast effects than non-aluminized HE. Objective is to develop benchtop system for dynamic x-ray diffraction (XRD) of aluminized HE.
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
Flash x-ray radiography analysis of detonation wave propagation in additive-manufactured high explosives
Recent research has demonstrated that additive manufacturing (AM) can be used to produce directionally sensitive high explosives (HEs), but detonation wave propagation in AM HEs with variable internal structure has not been studied. In this work, samples were printed using a 73 wt. % octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine-based HE ink. Flash x-ray radiography imaging was used to observe density changes in two imaging planes of each sample during detonation, and high-speed imaging was used to calculate the detonation velocity at the HE surface. The detonation front initially appears to fail in internal channel regions of the HE, but late reactions occurred in two samples, which increased the material bulk density by 2.8%, possibly due to shock convergence phenomena. The calculated detonation wave pressure similarly increased, but the accuracy of the results is uncertain because of the deviation of the low bulk density printed samples from the cast charge principal isentrope. Here, this work demonstrates that structure can be effectively utilized to guide detonation wave propagation through HE charges.
3D printing↗
Experimental observations of exploding bridgewire detonator function
Exploding bridgewire detonators are an industry standard technology used for over 75 years and valued for their precise timing and safety characteristics. Despite widespread use, their functional mechanism remains controversial with both shock and non-shock mechanisms attributed. In this work, we re-examine bridgewire detonator function with a suite of modern diagnostics and compare these observations with the existing literature. Traditional detonator observations consisted of voltage applied to the bridgewire and time dependent current, integral response measurements such as case motion and more recently Schlieren imaging of the detonator surface. In this work, we add visible light emission, X-ray transmission, proton radiography, and temperature measurements during detonator function in addition to voltage, current, and function times. The addition of in-situ observations of light emission, temperature, and density gives us new insight into the mechanisms of explosive bridgewire detonator function. We see a distinct separation in time, location, symmetry, and velocity of bridgewire output and detonation onset. During the time between bridgewire burst and the initiation of detonation, we observe a temperature ramp in the input pellet. In this paper, we present the suite of measurements and comparisons with the literature on integral response measurements.
42 ENGINEERING↗