Michael E. Rutherford

Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

Scintillator performance in time-resolved, hard, indirect detection X-ray studies on the sub-microsecond timescale at synchrotron light sources is reviewed, modelled and examined experimentally. LYSO:Ce is found to be the only commercially available crystal suitable for these experiments.

Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale

Chondritic meteorites are fragments of asteroids, the building blocks of planets, that retain a record of primordial processes. Important in their early evolution was impact-driven lithification, where a porous mixture of millimetre-scale chondrule inclusions and sub-micrometre dust was compacted into rock. In this Article, the shock compression of analogue precursor chondrite material was probed using state of the art dynamic X-ray radiography. Spatially-resolved shock and particle velocities, and shock front thicknesses were extracted directly from the radiographs, representing a greatly enhanced scope of data than could be measured in surface-based studies. A statistical interpretation of the measured velocities showed that mean values were in good agreement with those predicted using continuum-level modelling and mixture theory. However, the distribution and evolution of wave velocities and wavefront thicknesses were observed to be intimately linked to the mesoscopic structure of the sample. This Article provides the first detailed experimental insight into the distribution of extreme states within a shocked powder mixture, and represents the first mesoscopic validation of leading theories concerning the variation in extreme pressure-temperature states during the formation of primordial planetary bodies.

Interrogating heterogeneous compaction of analogue materials at the mesoscale through numerical modeling and experiments

Meteorites are classified by their relative exposure to three processes: aqueous alteration; thermal metamorphism; and shock processes. They constitute the main evidence available for the conditions in the early solar system. The precursor material to meteorites was bimodal and consisted of large spherical melt droplets (chondrules) surrounded by an extremely fine porous dust (matrix) with a high bulk porosity (> 50%). We present experiments and simulations, developed in tandem, investigating the heterogeneous compaction of matter analogous to these precursor materials. Experiments were performed at the European Synchrotron Radiation Facility (ESRF) where radiographs of the shock compaction and wave propagation were taken in-situ and in real time. Mesoscale simulations were performed using a shock physics code to investigate the heterogeneous response of these mixtures to shock loading. Two simple scenarios were considered in which the compacted material was pure matrix or pure matrix with a single inclusion. Good agreement was found between experiment and model in terms of shock position and relative compaction in the matrix. In addition, spatial variation in post-shock compaction was observed around the single inclusion despite uniform pre-shock porosity in the matrix. This shock-induced anisotropy in compaction could provide a new way of decoding the magnitude and direction by which a meteorite was shocked in the past.