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Conference paperTear GR, Chapman DJ, Eakins D, et al., 2017,
Birefringence measurements in single crystal sapphire and calcite shocked along the a axis
, Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter, Publisher: AIP Publishing, ISSN: 1551-7616Calcite and sapphire were shock compressed along the ⟨101⎯⎯0⟩ direction (a axis) in a plate impact configuration. Polarimetery and Photonic Doppler Velocimetery (PDV) were used to measure the change in birefringence with particle velocity in the shock direction. Results for sapphire agree well with linear photoelastic theory and current literature showing a linear relationship between birefringence and particle velocity up to 310 m s−1. A maximum change in birefringence of 5% was observed. Calcite however showed anomolous behaviour with no detectable change in birefringence (less than 0.1%) over the range of particle velocities studied (up to 75 m s−1).
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Conference paperBell DJ, Chapman DJ, 2017,
Phase Doppler Anemometry as an Ejecta Diagnostic
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperJones DR, Chapman DJ, Eakins DE, 2017,
Gas Gun Driven Dynamic Fracture and Fragmentation of Ti-6Al-4V Cylinders at Initial Temperatures Between 150 K and 750 K
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperNguyen T-TN, Proud WG, 2017,
An Investigation of A Reticulated Foam - Perforated Steel Sheet Combination As A Blast Mitigation Structure
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperKhan AS, Proud WG, 2017,
Temperature and Strain Rate Effects on the Piezoelectric Charge Production of PZT 95/5
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperKhan AS, Wilgeroth J, Balzer J, et al., 2017,
Comparison of Epoxy-Based Encapsulating Materials over Temperature and Strain Rate
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperIrwin R, White S, Warwick JR, et al., 2017,
Study of Ar photoionisation physics using VULCAN
The values achieved for the photoionisation parameter (ξ) are, to our knowledge, the highest to be achieved in the laboratory. This will benefit future understanding of the physics of numerous astrophysical bodies such as Seyfert galaxies. A possible future experiment would be to try to achieve a higher value for ξ at a larger laser facility such as GEKKO, NIF or OMEGA, and to extend the study to other gases such as Neon.
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Conference paperButler BJ, Sory DR, Nguyen T-TN, et al., 2017,
Characterization of Focal Muscle Compression Under Impact Loading
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperBadham H, Chalmers M, Thuy-Tien NN, et al., 2017,
The Propagation of Blast Pulses through Dampened Granular Media
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AIP Publishing, ISSN: 1551-7616The propagation of stress through granular and dampened granular material has been reported previously, the addition of significant amounts of liquid in granular beds causes the mechanism of transmission of blast from one of percolation through the bed pores to one of stress transmission through the granules of the bed. It has been shown, however, that limited amounts liquid can retard propagation within blast-loaded beds by approximately an order of magnitude. This paper presents data on percolation through dampened granular beds using a shock tube as the pressure driver. The effect of particle shape and size was investigated using angular grains of quartz sand as well as smooth glass microspheres. The effect of addition of small amounts of liquids is presented.
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Conference paperProud WG, Chapman DJ, Eakins DE, 2017,
The stress and ballistic properties of granular materials
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AIP Publishing, ISSN: 1551-7616Granular materials are widespread in nature and in manufacturing. Their particulate nature gives a compressive strength of a similar order of magnitude as many continuous solids, a vanishingly small tensile strength and variable shear strength, highly dependent on the loading conditions. Previous studies have shown the effect of composition, morphology and particle size, however, compared to metals and polymers, granular materials are not so well understood. This paper will present some recent results for granular materials, placing these within the wider context. Two areas will be dealt with (i) the effect of the skeletal strength of the material and (ii) the displacements associated with ballistic impact. One clear observation is the similarity of behavior of quartz-sands in compression across a range of particle size. However, the precise pathway of compression is strongly dependent on the initial conditions e.g. density and connectivity within the granular bed, as emphasized by some data for quasi-static compression of sand. To fully embrace the range of behaviours seen requires the development of a suitable parameter to describe the material, the paper concludes with a discussion of one of those approaches.
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Conference paperSory DR, Areias AC, Overby DR, et al., 2017,
Novel method to dynamically load cells in 3D-hydrogels culture for blast injury studies
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperTear GR, Proud WG, 2017,
Predicting the Optical Behaviour of Shock Compressed Dielectrics
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Book chapterRose S, 2017,
Particle Interactions in High-Temperature Plasmas Supervisor's Foreword
, PARTICLE INTERACTIONS IN HIGH-TEMPERATURE PLASMAS, Publisher: SPRINGER-VERLAG BERLIN, Pages: V-V, ISBN: 978-3-319-63446-3 -
Journal articleWinter RE, Stirk SM, Harris EJ, et al., 2016,
A technique for studying the response of materials to high rate, high strain deformation
, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 97, Pages: 116-126, ISSN: 0734-743X -
Journal articleTorchio R, Occelli F, Mathon O, et al., 2016,
Probing local and electronic structure in Warm Dense Matter: single pulse synchrotron x-ray absorption spectroscopy on shocked Fe
, Scientific Reports, Vol: 6, ISSN: 2045-2322Understanding Warm Dense Matter (WDM), the state of planetary interiors, is a new frontier in scienti c research. There exists very little experimental data probing WDM states at the atomic level to test current models and those performed up to now are limited in quality. Here, we report a proof-of- principle experiment that makes microscopic investigations of materials under dynamic compression easily accessible to users and with data quality close to that achievable at ambient. Using a single100 ps synchrotron x-ray pulse, we have measured, by K-edge absorption spectroscopy, ns-lived equilibrium states of WDM Fe. Structural and electronic changes in Fe are clearly observed for the rst time at such extreme conditions. The amplitude of the EXAFS oscillations persists up to 500 GPa and 17000 K, suggesting an enduring local order. Moreover, a discrepancy exists with respect to theoretical calculations in the value of the energy shift of the absorption onset and so this comparison should help to re ne the approximations used in models.
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Thesis dissertationNguyen TT, 2016,
The Characterisation of A Shock Tube System for Blast Injury Studies
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Journal articlePike OJ, Rose SJ, 2016,
Transport coefficients of a relativistic plasma
, Physical Review E, Vol: 93, ISSN: 1539-3755In this work, a self-consistent transport theory for a relativistic plasma is developed.Using the notation of Braginskii [S. I. Braginskii, in Reviews of Plasma Physics, ed. M. A.Leontovich (1965), Vol. 1, p.174], we provide semi-analytical forms of the electrical resistivity,thermoelectric and thermal conductivity tensors for a Lorentzian plasma in a magnetic field.This treatment is then generalized to plasmas with arbitrary atomic number by numericallysolving the linearized Boltzmann equation. The corresponding transport coefficients arefitted by rational functions in order to make them suitable for use in radiation-hydrodynamicsimulations and transport calculations. Within the confines of linear transport theory andon the assumption that the plasma is optically thin, our results are valid for temperatures upto a few MeV. By contrast, classical transport theory begins to incur significant errors abovekBT ∼ 10 keV, e.g., the parallel thermal conductivity is suppressed by 15% at kBT = 20keV due to relativistic effects
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Journal articleSwadling GF, Lebedev SV, Hall GN, et al., 2016,
Experimental investigations of ablation stream interaction dynamics in tungsten wire arrays: interpenetration, magnetic field advection, and ion deflection
, Physics of Plasmas, Vol: 23, ISSN: 1089-7674Experiments have been carried out to investigate the collisional dynamics of ablation streams produced by cylindrical wire array z-pinches. A combination of laser interferometric imaging, Thomson scattering, and Faraday rotationimaging has been used to make a range of measurements of the temporal evolution of various plasma and flow parameters. This paper presents a summary of previously published data, drawing together a range of different measurements in order to give an overview of the key results. The paper focuses mainly on the results of experiments with tungsten wire arrays. Early interferometric imagingmeasurements are reviewed, then more recent Thomson scattering measurements are discussed; these measurements provided the first direct evidence of ablation stream interpenetration in a wire array experiment. Combining the data from these experiments gives a view of the temporal evolution of the tungsten stream collisional dynamics. In the final part of the paper, we present new experimental measurements made using an imagingFaraday rotationdiagnostic. These experiments investigated the structure of magnetic fields near the array axis directly; the presence of a magnetic field has previously been inferred based on Thomson scattering measurements of ion deflection near the array axis. Although the Thomson and Faradaymeasurements are not in full quantitative agreement, the Faraday data do qualitatively supports the conjecture that the observed deflections are induced by a static toroidal magnetic field, which has been advected to the array axis by the ablation streams. It is likely that detailed modeling will be needed in order to fully understand the dynamics observed in the experiment.
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Journal articleHaerendel G, Suttle L, Lebedev SV, et al., 2016,
Stop layer: a flow braking mechanism in space and support from a lab experiment
, Plasma Physics and Controlled Fusion, Vol: 58, ISSN: 1361-6587The paper presents short summaries and a synopsis of two completely independent discoveries of a fast flow braking process, one realized by a laboratory experiment (Lebedev et al 2014 Phys. Plasmas 21 056305), the other by theoretical reasoning stimulated by auroral observation (Haerendel 2015a J. Geophys. Res. Space Phys. 120 1697–714). The first has been described as a magnetically mediated sub-shock forming when a supersonic plasma flow meets a wall. The second tried to describe what happens when a high-beta plasma flow from the central magnetic tail meets the strong near-dipolar field of the magnetosphere. The term stop layer signals that flow momentum and energy are directly coupled to a magnetic perturbation field generated by a Hall current within a layer of the width of c/ω pi and immediately propagated out of the layer by kinetic Alfvén waves. As the laboratory situation is not completely collision-free, energy transfer from ions to electrons and subsequent radiative losses are likely to contribute. A synopsis of the two situations identifies and discusses six points of commonality between the two situations. It is pointed out that the stop layer mechanism can be regarded as a direct reversal of the reconnection process.
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Journal articleSherlock M, Rozmus W, Hill EG, et al., 2016,
Sherlock et al. Reply
, Physical Review Letters, Vol: 116, ISSN: 1079-7114 -
Journal articleRutherford ME, Chapman DJ, White TG, et al., 2016,
Evaluating scintillator performance in time-resolvedhard X-ray studies at synchrotron light sources
, Journal of Synchrotron Radiation, Vol: 23, ISSN: 1600-5775The short pulse duration, small effective source size and high flux of synchrotronradiation is ideally suited for probing a wide range of transient deformationprocesses in materials under extreme conditions. In this paper, the challenges ofhigh-resolution time-resolved indirect X-ray detection are reviewed in thecontext of dynamic synchrotron experiments. In particular, the discussion istargeted at two-dimensional integrating detector methods, such as those focusedon dynamic radiography and diffraction experiments. The response of ascintillator to periodic synchrotron X-ray excitation is modelled and validatedagainst experimental data collected at the Diamond Light Source (DLS) andEuropean Synchrotron Radiation Facility (ESRF). An upper bound on thedynamic range accessible in a time-resolved experiment for a given bunchseparation is calculated for a range of scintillators. New bunch structures aresuggested for DLS and ESRF using the highest-performing commerciallyavailable crystal LYSO:Ce, allowing time-resolved experiments with aninterframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).
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Journal articleJung A, Pullen AD, Proud WG, 2016,
Strain-rate effects in Ni/Al composite metal foams from quasi-static to low-velocity impact behaviour
, Composites Part A - Applied Science and Manufacturing, Vol: 85, Pages: 1-11, ISSN: 1359-835XMetal foams are used as absorbers for kinetic energy but predominantly, they have only been investigated under quasi-static load-conditions. Coating of open-cell metal foams improves the mechanical properties by forming of Ni/Al hybrid foam composites. The properties are governed by the microstructure, the strut material and geometry. In this study, the strain-rate effects in open-cell aluminium foams and new Ni/Al composite foams are investigated by quasi-static compression tests and low-velocity impact. For the first time, drop weight tests are reported on open-cell metal foams, especially Ni/Al composite foams. Furthermore, size-effects were evaluated. The microstructural deformation mechanism was analysed using a high-speed camera and digital image correlation. Whereas pure aluminium foams are only strain-rate sensitive in the plastic collapse stress, Ni/Al foams show a general strain-rate sensitivity based on microinertia effects and the rate-sensitive nano-nickel coating. Ni/Al foams are superior to aluminium foams and to artificial aluminium foams with equal density.
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Journal articleTurrell AE, Sherlock M, Rose SJ, 2016,
Efficient evaluation of collisional energy transfer terms for plasma particle simulations
, JOURNAL OF PLASMA PHYSICS, Vol: 82, ISSN: 0022-3778 -
Journal articleEftaxiopoulou T, Barnett-Vanes A, Arora H, et al., 2016,
Prolonged but not short duration blast waves elicit acute inflammation in a rodent model of primary blast limb trauma
, Injury, Vol: 47, Pages: 625-632, ISSN: 0020-1383BackgroundBlast injuries from conventional and improvised explosive devices account for 75% of injuries from current conflicts; of these over 70% involve the limbs. Variable duration and magnitude of blast wave loading occurs in real-life explosions and is hypothesised to cause different injuries. While a number of in-vivo models report the inflammatory response to blast injuries, the extent of this response has not been investigated with respect to the duration of the primary blast wave. The relevance is that explosions in open air are of short duration compared to those in confined spaces. MethodsHind limbs of adult Sprauge-Dawley rats were subjected to focal isolated primary blast waves of varying overpressure (1.8-3.65kPa) and duration (3.0-11.5ms), utilising a shock tube and purpose built experimental rig. Rats were monitored during and after blast. At 6 and 24hrs after exposure blood, lungs, liver and muscle tissue were collected and prepared for histology and flow cytometry.ResultsAt 6hrs increases in circulating neutrophils and CD43Lo/His48Hi monocytes were observed in rats subjected to longer duration blast waves. This was accompanied by increases in circulating pro-inflammatory chemo/cytokines KC and IL-6. No changes were observed with shorter duration blast waves irrespective of overpressure. In all cases, no histological damage was observed in muscle, lung or liver. By 24hrs post-blast all inflammatory parameters had normalised. ConclusionsWe report the development of a rodent model of primary blast limb trauma that is the first to highlight an important role played by blast wave duration and magnitude in initiating acute inflammatory response following limb injury in the absence of limb fracture or penetrating trauma. The combined biological and mechanical method developed can be used to further understand the complex effects of blast waves in a range of different tissues and organs in-vivo.
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Journal articleSuzuki-Vidal F, Lebedev SV, Ciardi A, et al., 2015,
BOW SHOCK FRAGMENTATION DRIVEN BY A THERMAL INSTABILITY IN LABORATORY ASTROPHYSICS EXPERIMENTS
, Astrophysical Journal, Vol: 815, ISSN: 1538-4357The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counterstreaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE pulsed-power generator. The jets have different flow velocities in the laboratory frame, and the experiments are driven over many times the characteristic cooling timescale. The initially smooth bow shock rapidly develops small-scale nonuniformities over temporal and spatial scales that are consistent with a thermal instability triggered by strong radiative cooling in the shock. The growth of these perturbations eventually results in a global fragmentation of the bow shock front. The formation of a thermal instability is supported by analysis of the plasma cooling function calculated for the experimental conditions with the radiative packages ABAKO/RAPCAL.
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Journal articleBurdiak GC, Lebedev SV, Harvey-Thompson AJ, et al., 2015,
Characterisation of the current switch mechanism in two-stage wire array Z-pinches
, Physics of Plasmas, Vol: 22, ISSN: 1089-7674In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA,240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inversewire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wirearray, before rapidly switching the majority of the generator current into the load after a100–150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse ispresented. Measurements of the load resistivity and energy deposition suggest significant bulk heatingof the array mass occurs. The 5 kA pre-pulse delivers 0.8 J of energy to the load, leaving itin a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse arraybegins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicatethat the main current switch may evolve in part as a plasma flow switch, driven by the expansionof a magnetic cavity and plasma bubble along the length of the load array. Analysis ofimplosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, correspondingto a doubling of the generator dI/dt. Potential scaling of the device to higher currentmachines is discussed. V
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Journal articleTurrell A, Sherlock M, Rose SJ, 2015,
Ultra-fast collisional ion heating by electrostatic shocks
, Nature Communications, Vol: 6, ISSN: 2041-1723High intensity lasers can be used to generate shockwaves which have found applications in nuclear fusion, proton imaging, cancer therapies, and materials science. Collisionless electrostatic shocks are one type of shockwave widely studied for applications involving ion acceleration. Here we show a novel mechanism for collisionlesselectrostatic shocks to heat small amounts of solid density matter to temperatures of ∼ keV in tens of femtoseconds. Unusually, electrons play no direct role in the heating, and it is the ions which determine the heating rate. Ions are heated due to an interplay between the electric field of the shock, the local density increaseduring the passage of the shock, and collisions between different species of ion. In simulations, these factors combine to produce rapid, localised heating of the lighter ion species. Although the heated volume is modest, this would be one of the fastest heating mechanisms discovered if demonstrated in the laboratory.
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Journal articleProud WG, Nguyen T-TN, Bo C, et al., 2015,
The High-Strain Rate Loading of Structural Biological Materials
, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 46A, Pages: 4559-4566, ISSN: 1073-5623- Author Web Link
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Journal articleProud WG, Williamson DM, Field JE, et al., 2015,
Diagnostic techniques in deflagration and detonation studies
, Chemistry Central Journal, Vol: 9, ISSN: 1752-153XAdvances in experimental, high-speed techniques can be used to explore the processes occurring within energetic materials. This review describes techniques used to study a wide range of processes: hot-spot formation, ignition thresholds, deflagration, sensitivity and finally the detonation process. As this is a wide field the focus will be on small-scale experiments and quantitative studies. It is important that such studies are linked to predictive models, which inform the experimental design process. The stimuli range includes, thermal ignition, drop-weight, Hopkinson Bar and Plate Impact studies. Studies made with inert simulants are also included as these are important in differentiating between reactive response and purely mechanical behaviour.
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Conference paperShahzad M, Tallents GJ, Culfa O, et al., 2015,
Diagnosis of Radiation Heating in Iron Buried Layer Targets
, 14th International Conference on X-Ray Lasers, Publisher: Springer, Pages: 411-416, ISSN: 0930-8989Extreme ultra-violet (EUV) laboratory lasers can be used to probe energy transport in laser irradiated solid targets. We report on a recent experiment undertaken at LASERIX whereby the heating of laser-irradiated targets containing a thin layer of iron (50 nm) encased in plastic (CH) was diagnosed using EUV laser (13.9 nm) back-lighter probing. The heating laser pulse duration was 35fs with focal irradiances of 3×10163×1016Wcm−2−2 and a deliberate prepulse 20 ps before the main pulse at irradiances of 3×10153×1015Wcm−2−2. A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission using IMP opacity values for the iron layer and the simulated transmissions compared to measured transmission values. When a deliberate prepulse is used to preform an expanding plastic plasma, it is found that radiation heating is dominant in the heating of the iron layer giving rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9nm laser radiation as the iron ionizes to Fe5+5+ and above.
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