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Conference paperTear GR, Chapman DJ, Proud WG, et al., 2018,
The use of PDV to understand damage in rocket motor propellants
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AIP Publishing, ISSN: 1551-7616Photonic Doppler Velocimetry (PDV) has been fielded on small scale fragment impact experiments on double base propellant. A 130 mm block of propellant was impacted with a 20 mm diameter cylinder at 1003 ± 10 m s-1 and four PDV probes recorded rear surface motion at different radial distances between 10 mm and 60 mm from impact centre. The PDV was fielded alongside high speed video diagnostics using a dichroic mirror which reflected visible light whilst transmitting the 1550 nm wavelength which the PDV operated at. The rear surface velocity was compared to 2D numerical simulations of the experiment and found to be in good agreement. Additional material moving at up to 2 km s-1 was detected at break out.
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Conference paperNguyen T-TN, Tear GR, Masouros SD, et al., 2018,
Fragment Penetrating Injury to Long Bones
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperSmith LC, Chapman DJ, Hooper PA, et al., 2018,
On the Dynamic Response of Additively Manufactured 316L
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperBrown KA, Butler BJ, Sory D, et al., 2018,
Challenges in the Characterization of Failure and Resilience of Biological Materials
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperOta TA, Chapman DJ, Richley JC, et al., 2018,
Initial Results From a Simultaneous Pyrometry and Reflectivity Diagnostic
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Journal articlede Grouchy PWL, Kusse BR, Banasek J, et al., 2018,
Observations of the magneto-Rayleigh-Taylor instability and shock dynamics in gas-puff Z-pinch experiments
, PHYSICS OF PLASMAS, Vol: 25, ISSN: 1070-664X -
Conference paperTear G, Cohen A, Magnus D, et al., 2018,
Damage characterisation for cement and concrete using microwave induced damage
, International Conference on Experimental Mechanics, Publisher: MDPI, ISSN: 2504-3900Damage leading to failure in concrete and related materials is a complex behavior. Whilst many numerical approaches are available for simulating the degradation of material strength, it is difficult to discriminate between these models experimentally in the high strain rate ballistic impact regime. An experimental method has been developed to determine when local material failure has occurred, and whether the failure can be classed as fracture or granular flow. This method is tested on Kolsky bar and ballistic impact experiments. Comparison with numerical simulations is presented.
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Journal articleEscauriza EM, Olbinado MP, Rutherford ME, et al., 2018,
Ultra-high-speed indirect x-ray imaging system with versatile spatiotemporal sampling capabilities
, APPLIED OPTICS, Vol: 57, Pages: 5004-5010, ISSN: 1559-128X -
Journal articleWhite S, Irwin R, Warwick R, et al., 2018,
Production of photoionized plasmas in the laboratory using X-ray line radiation
, Physical Review E, Vol: 97, ISSN: 1539-3755In this paper we report the experimental implementation of a theoretically proposed technique for creating a photoionized plasma in the laboratory using x-ray line radiation. Using a Sn laser plasma to irradiate an Ar gas target, the photoionization parameter, ξ=4πF/Ne, reached values of order 50ergcms−1, where F is the radiation flux in ergcm−2s−1. The significance of this is that this technique allows us to mimic effective spectral radiation temperatures in excess of 1 keV. We show that our plasma starts to be collisionally dominated before the peak of the x-ray drive. However, the technique is extendable to higher-energy laser systems to create plasmas with parameters relevant to benchmarking codes used to model astrophysical objects.
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Journal articleMillett JCF, Higgins DL, Chapman DJ, et al., 2018,
The Effects of Prior Cold Work on the Shock Response of Copper
, Journal of Dynamic Behavior of Materials, Vol: 4, Pages: 211-221, ISSN: 2199-7446 -
Journal articleNguyen TN, Sory DR, Rankin SM, et al., 2018,
Platform development for primary blast injury studies
, Trauma (United Kingdom), ISSN: 1460-4086© 2018, The Author(s) 2018. Explosion-related injuries are currently the most commonly occurring wounds in modern conflicts. They are observed in both military and civilian theatres, with complex injury pathophysiologies. Primary blast injuries are the most frequently encountered critical injuries experienced by victims close to the explosion. They are caused by large and rapid pressure changes of the blast waves which produce a wide range of loading patterns resulting in varied injuries. Well-characterised experimental loading devices which can reproduce the real mechanical characteristics of blast loadings on biological specimens in in vivo, ex vivo, and in vitro models are essential in determining the injury mechanisms. This paper discusses the performance and application of platforms, including shock tubes, mechanical testing machines, drop-weight rigs, and split-Hopkinson pressure bar, with regards to the replication of primary blast.
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Journal articleGurovich V, Virozub A, Rososhek A, et al., 2018,
Quasi-isentropic compression using compressed water flow generated by underwater electrical explosion of a wire array
, Journal of Applied Physics, Vol: 123, ISSN: 0021-8979A major experimental research area in material equation-of-state today involves the use of off-Hugoniot measurements rather than shock experiments that give only Hugoniot data. There is a wide range of applications using quasi-isentropic compression of matter including the direct measurement of the complete isentrope of materials in a single experiment and minimizing the heating of flyer plates for high-velocity shock measurements. We propose a novel approach to generating quasi-isentropic compression of matter. Using analytical modeling and hydrodynamic simulations, we show that a working fluid composed of compressed water, generated by an underwater electrical explosion of a planar wire array, might be used to efficiently drive the quasi-isentropic compression of a copper target to pressures ∼2 × 10 11 Pa without any complex target designs.
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Journal articleRose SJ, Santos JJ, Bailly-Grandvaux M, et al., 2018,
Laser-driven strong magnetostatic fields with applications to charged beam transport and magnetized high energy-density physics
, Physics of Plasmas, Vol: 25, ISSN: 1070-664XPowerful laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets,yielding magnetostatic fields (B-fields) in excess of 0.5 kT. The quasi-static currents are provided from hotelectron ejection from the laser-irradiated surface. According to our model, which describes the evolution ofthe discharge current, the major control parameter is the laser irradianceIlasλ2las. The space-time evolutionof the B-fields is experimentally characterized by high-frequency bandwidth B-dot probes and by proton-deflectometry measurements. The magnetic pulses, of ns-scale, are long enough to magnetize secondary targetsthrough resistive diffusion. We applied it in experiments of laser-generated relativistic electron transportthrough solid dielectric targets, yielding an unprecedented 5-fold enhancement of the energy-density flux at60μm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetizedhigh-energy density physics investigations, related to laser-generated secondary sources of radiation and/orhigh-energy particles and their transport, to high-gain fusion energy schemes and to laboratory astrophysics.
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Journal articleHill EG, Perez-Callejo G, Rose SJ, 2018,
ALICE: A non-LTE plasma atomic physics, kinetics and lineshape code
, High Energy Density Physics, Vol: 26, Pages: 56-67, ISSN: 1574-1818All three parts of an atomic physics, atomic kinetics and lineshape code, ALICE, are described. Examples of the code being used to model the emissivity and opacity of plasmas are discussed and interesting features of the code which build on the existing corpus of models are shown throughout.
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Conference paperDerrick J, Rutherford M, Davison T, et al., 2018,
Interrogating Heterogeneous Compaction of Analogue Materials at the Mesoscale Through Numerical Modeling and Experiments
, 20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter, Publisher: AIP Publishing, ISSN: 1551-7616 -
Journal articleZhang X, Wang G, Luo B, et al., 2018,
Mechanical response of near-equiatomic NiTi alloy at dynamic high pressure and strain rate
, Journal of Alloys and Compounds, Vol: 731, Pages: 569-576, ISSN: 0925-8388Understanding the behavior of near equi-atomic NiTi alloys under high strain rates and high pressures is important for the development of shock mitigating structures, particularly those that protect satellite and space vehicles from the impact of hyper velocity space debris. In this paper, the equation of state and constitutive relationships of NiTi alloy at pressures of 20–50 GPa and strain rates from 104s−1 to 107s−1 were investigated by means of magnetically driven quasi-isentropic compression and by shock compression from the impact of magnetically launched flyer plates. An inflection point at a pressure of 2–3 GPa was found on plots of Lagrangian sound speed versus particle velocity in both quasi-isentropic and shock compression experiments, and it shows the elastic-plastic transition of austenitic NiTi alloy. The effect of the strain rate on the elastic limit of NiTi alloy was clearly seen between strain rates of 104s−1 and 107s−1. We also found that the bulk sound speed calculated from the shock data was lower than that deduced from the ultrasonic measurements. Finally, a rate dependent Johnson–Cook model was modified to describe the dynamic responses of NiTi. With this modified model, hydrodynamic simulations agreed well with our observations.
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Conference paperMagnus D, Smith LC, Proud WG, 2018,
Multiple Wave Compression of Granular Materials Using the Split-Hopkinson Pressure Bar
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperMagnus D, Haller A, Jouffroy A, et al., 2018,
Tensile Characterisation of the Aorta across Quasi-static to Blast Loading Strain Rates
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperProud WG, Ellison K, Yapp SH, et al., 2018,
The Response of Simple Polymer Structures to Dynamic Loading
, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Journal articleRutherford ME, Chapman DJ, Derrick JG, et al., 2017,
Corrigendum: Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale.
, Scientific Reports, Vol: 7, Pages: 1-1, ISSN: 2045-2322This corrects the article DOI: 10.1038/srep45206.
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Journal articlearora H, nila A, Vitharana K, et al., 2017,
Microstructural consequences of blast lung injury characterised with digital volume correlation
, Frontiers in Materials, Vol: 4, ISSN: 2296-8016This study focuses on microstructural changes that occur within the mammalian lung when subject to blast and how these changes influence strain distributions within the tissue. Shock tube experiments were performed to generate the blast injured specimens (cadaveric Sprague-Dawley rats). Blast overpressures of 100 and 180 kPa were studied. Synchrotron tomography imaging was used to capture volumetric image data of lungs. Specimens were ventilated using a custom-built system to study multiple inflation pressures during each tomography scan. These data enabled the first digital volume correlation (DVC) measurements in lung tissue to be performed. Quantitative analysis was performed to describe the damaged architecture of the lung. No clear changes in the microstructure of the tissue morphology were observed due to controlled low- to moderate-level blast exposure. However, significant focal sites of injury were observed using DVC, which allowed the detection of bias and concentration in the patterns of strain level. Morphological analysis corroborated the findings, illustrating that the focal damage caused by a blast can give rise to diffuse influence across the tissue. It is important to characterize the non-instantly fatal doses of blast, given the transient nature of blast lung in the clinical setting. This research has highlighted the need for better understanding of focal injury and its zone of influence (alveolar interdependency and neighboring tissue burden as a result of focal injury). DVC techniques show great promise as a tool to advance this endeavor, providing a new perspective on lung mechanics after blast.
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Journal articleRose SJ, Keenan FP, Poppenhaeger K, et al., 2017,
X-ray line coincidence photopumping in a solar flare
, Monthly Notices of the Royal Astronomical Society, Vol: 474, Pages: 3782-3786, ISSN: 0035-8711Line coincidence photopumping is a process where the electrons of an atomic or molecular species are radiatively excited through the absorption of line emission from another species at a coincident wavelength. There are many instances of line coincidence photopumping in astrophysical sources at optical and ultraviolet wavelengths, with the most famous example being Bowen fluorescence (pumping of O III 303.80 Å by He II), but none to our knowledge in X-rays. However, here we report on a scheme where a He-like line of Ne IX at 11.000 Å is photopumped by He-like Na X at 11.003 Å, which predicts significant intensity enhancement in the Ne IX 82.76 Å transition under physical conditions found in solar flare plasmas. A comparison of our theoretical models with published X-ray observations of a solar flare obtained during a rocket flight provides evidence for line enhancement, with the measured degree of enhancement being consistent with that expected from theory, a truly surprising result. Observations of this enhancement during flares on stars other than the Sun would provide a powerful new diagnostic tool for determining the sizes of flare loops in these distant, spatially unresolved, astronomical sources.
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Journal articleYanuka D, Rososhek A, Bland SN, et al., 2017,
Uniformity of cylindrical imploding underwater shockwaves at very small radii
, Applied Physics Letters, Vol: 111, ISSN: 1077-3118We compare the convergent shockwaves generated from underwater, cylindrical arrays of copperwire exploded by multiple kilo-ampere current pulses on nanosecond and microsecond scales. Inboth cases, the pulsed power devices used for the experiments had the same stored energy ( 500 J)and the wire mass was adjusted to optimize energy transfer to the shockwave. Laser backlit framingimages of the shock front were achieved down to the radius of 30lm. It was found that even in thecase of initial azimuthal non-symmetry, the shock wave self-repairs in the final stages of its motion,leading to a highly uniform implosion. In both these and previous experiments, interference fringeshave been observed in streak and framing images as the shockwave approached the axis. We havebeen able to accurately model the origin of the fringes, which is due to the propagation of the laserbeam diffracting off the uniform converging shock front. The dynamics of the shockwave and itsuniformity at small radii indicate that even with only 500 J stored energies, this technique shouldproduce pressures above 10¹⁰Pa on the axis, with temperatures and densities ideal for warm densematter research.
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Journal articleOwen GD, Chapman DJ, Whiteman G, et al., 2017,
Spall behaviour of single crystal aluminium at three principal orientations
, Journal of Applied Physics, Vol: 122, ISSN: 0021-8979A series of plate impact experiments have been conducted to study the spall strength of the three principal crystallographic orientations of single crystal aluminium ([100], [110] and, [111]) and ultra-pure polycrystalline aluminium. The samples have been shock loaded at two impact stresses (4 GPa and 10 GPa). Significant differences have been observed in the elastic behaviour, the pullback velocities, and the general shape of the wave profiles, which can be accounted for by considerations of the microscale homogeneity, the dislocation density, and the absence of grain boundaries in the single crystal materials. The data have shown that there is a consistent order of spall strength measured for the four sample materials. The [111] orientation has the largest spall strength and elastic limit, followed closely by [110], [100], and then the polycrystalline material. This order is consistent with both quasi-static data and geometrical consideration of Schmid factors.
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Journal articleDavison TM, Derrick JG, Collins GS, et al., 2017,
Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments
, Procedia Engineering, Vol: 204, Pages: 405-412, ISSN: 1877-7058Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.
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Journal articleWhiteman G, Owen GD, De'Ath J, et al., 2017,
Spatially resolved measurements of grain size effects on the shock and spall response of quasi-Taylor wave loaded pure copper
, JOURNAL OF APPLIED PHYSICS, Vol: 122, ISSN: 0021-8979 -
Journal articleBland SN, Krasik YAE, Yanuka D, et al., 2017,
Generation of highly symmetric, cylindrically convergent shockwaves in water
, Physics of Plasmas, Vol: 24, ISSN: 1089-7674We report on pulsed power driven, exploding copper wire array experiments conducted to generate cylindrical convergent shockwaves in water employing μs risetime currents >550 kA in amplitude and with stored energies of >15 kJ—a substantial increase over previous results. The experiments were carried out on the recently constructed Mega-Ampere-Compression-and-Hydrodynamics facility at Imperial College London in collaboration with colleagues of Technion, Israel. 10 mm diameter arrays consisting of 60 × 130 μm wires were utilized, and the current and voltage diagnostics of the load region suggested that ∼8 kJ of energy was deposited in the wires (and the load region close to the wires) during the experiments, resulting in the formation of dense, highly resistive plasmas that rapidly expanded driving the shockwaves in water. Laser-backlit framing images of the shockfront were obtained at radii <0.25 mm for the first time, and there was strong evidence that even at radii <0.1 mm this front remains stable, resulting in a convergence ratio of >50:1. Framing images and streak photographs showed that the velocity of the shockwave reached ∼7.5 km s−1 at 0.1 mm from the axis. 2D hydrodynamic simulations that match the experimentally obtained implosion trajectory suggest that pressures >1 Mbar are produced within 10 μm of the axis along with water densities of 3gcm−3 and temperatures of many 1000 s of Kelvin. Under these conditions, Quotidian Equation of State suggests that a strongly coupled plasma with an ionization fraction of ∼0.7 would be formed. The results represent a “stepping stone” in the application of the technique to drive different material samples into high pressure, warm dense matter regimes with compact, university scale generators, and provide support in scaling the technique to multi-mega ampere
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Journal articleBurdiak GC, Lebedev SV, Bland SN, et al., 2017,
The structure of bow shocks formed by the interaction of pulsed-power driven magnetised plasma flows with conducting obstacles
, PHYSICS OF PLASMAS, Vol: 24, ISSN: 1070-664XWe present an experimental study of the development and structure of bow shocks produced by the interaction of a magnetised, collisional, super-Alfvénic plasma flow with conducting cylindrical obstacles. The plasma flow with an embedded, frozen-in magnetic field (ReM ∼ 20) is produced by the current-driven ablation of fine aluminium wires in an inverse, exploding wire array z-pinch. We show that the orientation of the embedded field with respect to the obstacles has a dramatic effect on the bow shock structure. When the field is aligned with the obstacle, a sharp bow shock is formed with a global structure that is determined simply by the fast magneto-sonic Mach number. When the field is orthogonal to the obstacle, magnetic draping occurs. This leads to the growth of a magnetic precursor and the subsequent development of a magnetised bow shock that is mediated by two-fluid effects, with an opening angle and a stand-off distance, that are both many times larger than in the parallel geometry. By changing the field orientation, we change the fluid regime and physical mechanisms that are responsible for the development of the bow shocks. MHD simulations show good agreement with the structure of well-developed bow shocks. However, collisionless, two-fluid effects will need to be included within models to accurately reproduce the development of the shock with an orthogonal B-field.
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Journal articleRutherford ME, Chapman DJ, Derrick JG, et al., 2017,
Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale
, Scientific Reports, Vol: 7, ISSN: 2045-2322Chondritic meteorites are fragments of asteroids, the building blocks of planets, that retain a record of primordialprocesses. 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 ofanalogue precursor chondrite material was probed using state of the art dynamic X-ray radiography. Spatially-resolvedshock and particle velocities, and shock front thicknesses were extracted directly from the radiographs, representinga greatly enhanced scope of data than could be measured in surface-based studies. A statistical interpretation of themeasured velocities showed that mean values were in good agreement with those predicted using continuum-levelmodelling and mixture theory. However, the distribution and evolution of wave velocities and wavefront thicknesseswere observed to be intimately linked to the mesoscopic structure of the sample. This Article provides the first detailedexperimental insight into the distribution of extreme states within a shocked powder mixture, and represents the firstmesoscopic validation of leading theories concerning the variation in extreme pressure-temperature states during theformation of primordial planetary bodies.
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Journal articleHoarty DJ, Sircombe N, Beiersdorfer P, et al., 2017,
Modelling K shell spectra from short pulse heated buried microdot targets
, High Energy Density Physics, Vol: 23, Pages: 178-183, ISSN: 1574-1818K shell X-ray emission measurements have been used to diagnose plasma conditions in short-pulse heated buried microdot targets on the Orion high power laser. These experiments have been used to validate simulations of short pulse laser-solid interaction that combine hybrid PIC modelling of the laser absorption with radiation-hydrodynamics simulations including an electron transport model. Comparison of these simulations with streaked K shell spectroscopy show the importance of including radial gradients in fitting the spectra. An example is presented of the emission of sulphur from a 50 µm diameter microdot sample buried in a plastic foil. Previously agreement between simulation and experiment was obtained only by treating the absorbed energy, electron temperature and beam divergence as fitting parameters. The good agreement obtained in this work used the measured laser energy and laser pulse length and calculated the laser-solid target interaction from first principles.
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