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Photon Doppler velocimetry (PDV) has become a standard diagnostic in impact and shock experiments, due to its relative flexibility and ease in alignment compared to other optical diagnostics. The conventional approach to fielding PDV in plate-impact experiments is to place probes directly down-range from the projectile and target. In experiments such as these, probes are almost certainly destroyed, resulting in significant replacement cost particularly when multiple probes are used. To overcome these shortcomings, a free-space optical relay system has been developed to focus multiple channels of PDV from outside an experimental tank onto a target of reduced size than the probe array. This system has been successfully tested on plate-impact experiments measuring a Hugoniot state of polycrystal tin, and the peak elastic stress and spall strength in 6082 aluminium alloy, in both cases adding information about the shock tilt to the experimental data generated. [ABSTRACT FROM AUTHOR]

Each year approximately 99% by mass of energetic material use takes place in the quarrying, mining, construction and petrochemical industries. The coupling of explosively driven shock waves to heterogeneous geological materials is of scientific and industrial relevance. Here we report the first experiments conducted with energetic materials at the ID19 beamline at the European Synchrotron Research Facility, Grenoble, France. The experiments used commercial detonators to explosively load sand samples and glass spheres. Time resolved images showing the compaction wave produced by the explosive loading of both coarse- and fine-grained sand as well as large and small diameter glass spheres. [ABSTRACT FROM AUTHOR]

The electric gun is a pulsed power projectile launcher, which utilizes the rapid expansion of an ohmically heated exploding foil to accelerate thin flyers up to 20 km/s. Though the launcher has the potential to access a largely unexplored thermodynamic space, the process of launching flyers above 0.25 mm thickness in this manner is highly variable, often resulting in uncontrolled launch characteristics and premature failure of the flyer. This behavior is challenging to diagnose experimentally, limiting the validation of numerical models and leaving uncertainties in material properties unresolved. This work presents the modelling, design, and experimental testing of a high energy electric gun load, utilizing a 1.2 MJ capacitor bank. Preliminary results reveal the successful launch of a 1.5 mm thick polymer flyer into a PMMA target block, generating impact pressures of 80 GPa. This advancement marks a stepping-stone towards optimising the electric gun to achieve even higher pressures and shock durations, enabling it to become a complimentary tool to existing projectile launch platforms. [ABSTRACT FROM AUTHOR]

The Photon Doppler Velocimetry (PDV) technique is used to capture simultaneously propagating elastic waves of longitudinal and shear nature in a Tension-Torsion Hopkinson Bar (TTHB) apparatus. The system uses a pair of probes per velocity measurement, which were taken on the opposite sides of the TTHB bar with a laser irradiated spot size of ~35 μm. The collected data were compared to the measurements obtained from the conventional strain gauge technique, and were in good agreement. The PDV method was effective in separating longitudinal and rotation signals even when they were superimposed on each other at the gauge location. This approach is also shown to be effective in detecting and accounting for the presence of bending waves in the TTHB bars. [ABSTRACT FROM AUTHOR]

In this work the dynamic fracturing of an ultra-high strength cementitious material is probed with in-situ ultra-high speed X-ray phase-contrast diagnostics to investigate the phenomenology of dynamic fracture. Gas gun experiments were conducted on two characteristic samples with two different impact speeds, namely 80 and 190 m/s using the edge-on impact test configuration. The samples were placed within the intense X-ray beam providing an observation field of 12.8 mm in width and 8 mm in height. Thanks to equispaced 16 bunches of short X-ray pulses, the samples were imaged through an indirect detector arrangement using the Shimadzu HPV-X2 camera lens-coupled to a fast scintillator capturing through-thickness measurements with an interframe time of 1.06 μs. The comparison of fragmentation patterns between two samples revealed an important insight into velocity dependant spall formation as well as the effects of crack closure and bridging. [ABSTRACT FROM AUTHOR]

Pyrometry is an established technique used in high strain rate experiments (such as plate impact experiments) whereby the temperature of a sample is determined from the measurement of collected thermal radiation. By applying Planck's Law, radiometry data can be used to determine temperature. A significant source of uncertainty in applying pyrometry to high strain rate experiments is due to possible changes in emissivity after a sample has been shocked; thus it is desirable to determine emissivity during the experiment. Kirchhoff's Law, which states emissivity is the complement of reflectivity, can be a pplied to determine emissivity in high strain rate experiments. Ideally the sample's reflectivity would be measured at the same wavelength and on the same experiment as the pyrometry measurement. A diagnostic has been developed which produces a modulated reflectivity signal that is insensitive to tilt and surface finish. Following characterisation of the system in the laboratory, dynamic tests were conducted. During the dynamic tests, the reflectivity signal was multiplexed onto the radiance signal allowing simultaneous measurement of radiance and reflectivity. A description of the diagnostic, results from laboratory t esting and r esults and analysis from dynamic experiments are presented. [ABSTRACT FROM AUTHOR]