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Journal articleRathee N, Keenan FP, Williams RJR, et al., 2026,
A comparison of time-dependent Cloudy astrophysical code simulations with experimental X-ray spectra from keV laser-generated argon plasmas
, Journal of Quantitative Spectroscopy and Radiative Transfer, Vol: 348, ISSN: 0022-4073We have generated strongly photoionized Ar plasmas in experiments designed to use primarily X-ray l-shell line emission generated from Ag foils irradiated by the VULCAN high-power laser at the UK Central Laser Facility. The principle of the experiment is that use of line emission rather than the usual sub-keV quasi-blackbody source allows keV radiation to play a more dominant role compared to softer X-rays and thus mimic the effect of a blackbody with a higher effective spectral temperature. Our aim is to reproduce in the laboratory the extreme photoionization conditions found in accretion-powered astrophysical sources. In this paper, we compare the experimental results on K-β X-ray Ar spectra with modelling using the time-dependent version of the Cloudy astrophysical code. The results indicate that photoionized laboratory plasmas can be successfully modelled with codes such as Cloudy that have been developed for application to astrophysical sources. Our comparison of simulation and experiment shows that the flux of sub-keV photons that photoionize the outer-shell electrons can have a significant effect, and that detailed measurements of the X-ray drive spectrum across all photon energy ranges are crucial for accurate modelling of experiments.
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Journal articleAsmedianov N, Grikshtas R, Pavlov S, et al., 2025,
Studies of specific action integral and electro-thermal instabilities in the sub-microsecond underwater electrical explosions of shaped foils
, JOURNAL OF APPLIED PHYSICS, Vol: 138, ISSN: 0021-8979 -
Journal articleBokman GT, Fiorini S, Strucka J, et al., 2025,
Planar shock-induced bubble collapse and jetting in water captured via x-ray phase contrast imaging
, Applied Physics Letters, Vol: 127, ISSN: 0003-6951Shock wave-bubble interactions in water manifest rich dynamics driven by a combination of strong pressure and density mismatches. They have a wide variety of applications, including the injection of pharmaceuticals, and through scaling, enable the exploration of various aspects of high-energy-density systems such as inertial confinement fusion. In this work, the interaction between a micrometric nitrogen bubble and a planar shock wave, characterized by a Mach number of M = 1.24 and a peak pressure of p max = 0.57 GPa, is experimentally recorded using ultra-high-speed x-ray phase contrast imaging. Highly resolved radiographs provide access to all phase discontinuities along the beam path, offering quantities such as the time-varying bubble size, the speed of a jet produced during the bubble collapse, and the time evolution of the shock wave front, which are critical benchmark data for numerical scheme validation. This study addresses the lack of well-characterized, repeatable, and high spatiotemporal resolution experiments at negative Atwood numbers by providing shock-bubble visualization and corresponding numerical simulation.
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Journal articleShahriari E, Gusev AI, Silvestre de Ferron A, et al., 2025,
Experimental and numerical simulation study of a semiconductor opening switch
, IEEE Transactions on Plasma Science, Vol: 53, Pages: 1583-1591, ISSN: 0093-3813This article examines the nanosecond interruption of high current in semiconductor opening switch (SOS) diodes, with the goal of bridging the gap between experimental results and numerical simulations. The experimental results of SOS diodes (0.25 cm2, 0.9 kV) operating as a nanosecond interrupter are presented in a wide range of cut-off current density from 300 A/cm2 to 5 kA/cm2 to analyze the two modes of operation, i.e., drift step recovery diode (DSRD) and SOS. In addition, the numerical simulations of the SOS diode are conducted to investigate the dynamics of the SOS diode in the DSRD and the SOS modes using the Synopsys TCAD. A mixed-mode device with a circuit simulator is utilized to simulate the SOS effect and the dynamic processes occurring during the current cut-off stage. Finally, the experimental and numerical simulation results of the SOS current and load voltage are compared indicating: 1) the accuracy of the TCAD model in the commercially available software, and 2) the possibility of operating the SOS diode in a DSRD mode.
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Journal articleGrikshtas R, Asmedianov N, Belozerov O, et al., 2025,
Electrothermal instabilities observed by x-ray radiography of underwater sub-microsecond electrical explosions of aluminum, silver, and molybdenum wires
, Physics of Plasmas, Vol: 32, ISSN: 1070-664XWe present measurements of the wavelength of electrothermal instabilities (ETI) formed during underwater electrical explosions of aluminum (Al), silver (Ag), and molybdenum (Mo) wires. Wires were exploded using a ∼450 ns rise time and ∼120 kA amplitude current pulse delivered by a pulse generator. Images of the exploding wires were captured by multi-frame synchrotron radiography at the ID19 beamline of the European Synchrotron Radiation Facility. Resolvable ETI was observed only in Al and Ag wires after the vaporization phase, whereas no such instabilities were detectable in Mo wires. Fourier analysis revealed that the ETI wavelengths in Al and Ag wires were comparable within the spatial resolution error, despite their different minimal instability wavelengths, which were predicted to develop during the melting phase. These minimal wavelengths were calculated using the linear ETI development theory and the simulated average wire temperature. The latter was calculated using one-dimensional hydrodynamic simulations, considering uniform current density across the wire cross-sectional area.
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Journal articleWatt R, Kettle B, Gerstmayr E, et al., 2025,
Bounding elastic photon-photon scattering at s≈1 MeV using a laser-plasma platform
, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 861, ISSN: 0370-2693We report on a direct search for elastic photon-photon scattering using x-ray and 𝛾 photons from a laser-plasmabased experiment. A 𝛾 photon beam produced by a laser wakeeld accelerator provided a broadband 𝛾 spectrumextending to above 𝐸𝛾 = 200 MeV. These were collided with a dense x-ray eld produced by the emission froma laser heated germanium foil at 𝐸𝑥 ≈ 1.4 keV, corresponding to an invariant mass of √𝑠 = 1.22 ± 0.22 MeV. Inthese asymmetric collisions elastic scattering removes one x-ray and one high-energy 𝛾 photon and outputs twolower energy 𝛾 photons. No changes in the 𝛾 photon spectrum were observed as a result of the collisions allowingus to place a 95% upper bound on the cross section of 1.5 × 1015 μb. Although far from the QED prediction, thisrepresents the lowest upper limit obtained so far for √𝑠 ≲ 1 MeV.
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Journal articleWahler S, Klapoetke TM, Proud WG, 2025,
Testing open-source tools for optical chemical structure recognition on novel nitrogen-rich energetic materials
, JOURNAL OF ENERGETIC MATERIALS, Vol: 43, Pages: 188-197, ISSN: 0737-0652- Cite
- Citations: 1
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Journal articleKettle B, Colgan C, Los E, et al., 2024,
Extended X-ray absorption spectroscopy using an ultrashort pulse laboratory-scale laser-plasma accelerator
, Communications Physics, Vol: 7, ISSN: 2399-3650Laser-driven compact particle accelerators can provide ultrashort pulses of broadband X-rays, well suited for undertaking X-ray absorption spectroscopy measurements on a femtosecond timescale. Here the Extended X-ray Absorption Fine Structure (EXAFS) features of the K-edge of a copper sample have been observed over a 250 eV window in a single shot using a laser wakefield accelerator, providing information on both the electronic and ionic structure simultaneously. This unique capability will allow the investigation of ultrafast processes, and in particular, probing high-energy-density matter and physics far-from-equilibrium where the sample refresh rate is slow and shot number is limited. For example, states that replicate the tremendous pressures and temperatures of planetary bodies or the conditions inside nuclear fusion reactions. Using high-power lasers to pump these samples also has the advantage of being inherently synchronised to the laser-driven X-ray probe. A perspective on the additional strengths of a laboratory-based ultrafast X-ray absorption source is presented.
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Journal articleRack A, Lukic B, Chapman DJ, et al., 2024,
Dynamic loading platforms coupled to ultra-high speed X-ray imaging at beamline ID19 of the European Synchrotron ESRF
, High Pressure Research, Vol: 44, Pages: 400-417, ISSN: 0895-7959The intersection of dynamic compression, high-rate material response and X-ray science has seen rapid growth, leading to the establishment of specialized end-stations at international facilities such as Linac Coherent Light Source LCLS (Matter at Extreme Conditions – MEC) and Advanced Photon Source APS (Dynamic Compression Sector – DCS), both USA. Although these facilities excel in working with X-rays tailored for small material volumes (i.e. <1mm3), it needs a different approach to delve into subsequent processes. This is particularly the case in the transition from the micro- to mesoscale: here the ESRF distinguishes itself. The large beam size (several cm2) of the ID19 beamline, in conjunction with a strong high energy component, source flux density, and outstanding imaging sensitivity, enables sub-surface visualization of engineering-scale structures as well as natural systems in representative volume, under high rate and shock. This is particularly valuable when studying materials with complex mesostructures and heterogeneities on relevant volumetric scales, which often dominate the dynamic material response. The study of the behavior of materials under dynamic loading presents a unique challenge due to inherently spanning over multiple lengths- and timescales. The evolution of sudden (thermo)mechanical excitation, starting from the lattice scale and progressing through grains, phase domains, and ultimately to structures, exhibits a spectrum of responses spanning from the microscopic to bulk length scales. Consequently, a diverse range of diagnostics as well as driver instrumentation is required to identify, study, and characterize this material response spectrum. This article shall introduce platforms available at beamline ID19 and underline their potential by selected showcase applications. Community access proposals such as the beamtime Block Allocation Group (BAG) allow for access in a routine manner.
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Journal articleRiley D, Singh RL, White S, et al., 2024,
Generation of photoionized plasmas in the laboratory of relevance to accretion-powered x-ray sources using keV line radiation
, High Energy Density Physics, Vol: 51, ISSN: 1574-1818We describe laboratory experiments to generate x-ray photoionized plasmas of relevance to accretion-powered xray sources such as neutron star binaries and quasars, with significant improvements over previous work. A keyquantity is referenced, namely the photoionization parameter, defined as ξ = 4πF/ne where F is the x-ray flux andne the electron density. This is normally meaningful in an astrophysical steady-state context, but is alsocommonly used in the literature as a figure of merit for laboratory experiments that are, of necessity, timedependent. We demonstrate emission-weighted values of ξ > 50 erg-cm s− 1 using laser-plasma x-ray sources,with higher results at the centre of the plasma which are in the regime of interest for several astrophysicalscenarios. Comparisons of laboratory experiments with astrophysical codes are always limited, principally by themany orders of magnitude differences in time and spatial scales, but also other plasma parameters. Howeveruseful checks on performance can often be made for a limited range of parameters. For example, we show thatour use of a keV line source, rather than the quasi-blackbody radiation fields normally employed in such experiments, has allowed the generation of the ratio of inner-shell to outer-shell photoionization expected from ablackbody source with ~keV spectral temperature. We compare calculations from our in-house plasma modellingcode with those from Cloudy and find moderately good agreement for the time evolution of both electrontemperature and average ionisation. However, a comparison of code predictions for a K-β argon X-ray spectrumwith experimental data reveals that our Cloudy simulation overestimates the intensities of more highly ionisedargon species. This is not totally surprising as the Cloudy model was generated for a single set of plasma conditions, while the experimental data are spatially integrated.
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Journal articleDowhan GV, Shah AP, Sporer BJ, et al., 2024,
High-magnification Faraday rotation imaging and analysis of X-pinch implosion dynamics
, Review of Scientific Instruments, Vol: 95, ISSN: 0034-6748An X-pinch load driven by an intense current pulse (>100 kA in ∼100 ns) can result in the formation of a small radius, runaway compressional micro-pinch. A micro-pinch is characterized by a hot (>1 keV), current-driven (>100 kA), high-density plasma column (near solid density) with a small neck diameter (1–10 μm), a short axial extent (<1 mm), and a short duration (.1 ns). With material pressures often well into the multi-Mbar regime, a micro-pinch plasma often radiates an intense, sub-ns burst of sub-keV to multi-keV x-rays. A low-density coronal plasma immediately surrounding the dense plasma neck could potentially shunt current away from the neck and thus reduce the magnetic drive pressure applied to the neck. To study the current distribution in the coronal plasma, a Faraday rotation imaging diagnostic (1064 nm) capable of producing simultaneous high-magnification polarimetric and interferometric images has been developed for the MAIZE facility at the University of Michigan. Designed with a variable magnification (1–10×), this diagnostic achieves a spatialresolution of approximately 35 μm, which is useful for resolving the ∼100-μm-scale coronal plasma immediately surrounding the dense core. This system has now been used on a reduced-output MAIZE (100–200 kA, 150 ns) to assess the radial distribution of drive current immediately surrounding the dense micro-pinch neck. The total current enclosed was found to increase as a function of radius, r, from a value of ≈ 50 ± 25 kA at r ≈ 140 μm (at the edge of the dense neck) to a maximal value of ≈ 150 ± 75 kA for r ≥ 225 μm. This corresponds to a peak magnetic drive pressure of ≈ 75 ± 50 kbar at r ≈ 225 μm. The limitations of these measurements are discussed in the paper.
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Journal articleXu L, Yu X, Favier CD, et al., 2024,
Development of an experimental method for well-controlled blast induced traumatic limb fracture in rats
, Defence Technology, Vol: 34, Pages: 168-176, ISSN: 2214-9147Heterotopic ossification (HO) is a consequence of traumatic bone and tissue damage, which occurs in 65% of military casualties with blast-associated amputations. However, the mechanisms behind blast-induced HO remain unclear. Animal models are used to study blast-induced HO, but developing such models is challenging, particularly in how to use a pure blast wave (primary blast) to induce limb fracture that then requires an amputation. Several studies, including our recent study, have developed platforms to induce limb fractures in rats with blast loading or a mixture of blast and impact loading. However, these models are limited by the survivability of the animal and repeatability of the model. In this study, we developed an improved platform, aiming to improve the animal's survivability and injury repeatability as well as focusing on primary blast only. The platform exposed only one limb of the rat to a blast wave while providing proper protection to the rest of the rat's body. We obtained very consistent fracture outcome in the tibia (location and pattern) in cadaveric rats with a large range of size and weight. Importantly, the rats did not obviously move during the test, where movement is a potential cause of uncontrolled injury. We further conducted parametric studies by varying the features of the design of the platform. These factors, such as how the limb is fixed and how the cavity through which the limb is placed is sealed, significantly affect the resulting injury. This platform and test setups enable well-controlled limb fracture induced directly by pure blast wave, which is the fundamental step towards a complete in vivo animal model for blast-induced HO induced by primary blast alone, excluding secondary and tertiary blast injury. In addition, the platform design and the findings presented here, particularly regarding the proper protection of the animal, have implications for future studies investigating localized blast injuries, such as blast induced br
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Journal articlePérez-Callejo G, Gawne T, Preston TR, et al., 2024,
Dielectronic satellite emission from a solid-density Mg plasma: relationship to models of ionization potential depression
, Physical Review E: Statistical, Nonlinear, and Soft Matter Physics, Vol: 109, ISSN: 1539-3755We report on experiments where solid-density Mg plasmas are created by heating with the focused output of the Linac Coherent Light Source x-ray free-electron laser. We study the K-shell emission from the helium- and lithium-like ions using Bragg crystal spectroscopy. Observation of the dielectronic satellites in lithium-like ions confirms that the M-shell electrons appear bound for these high charge states. An analysis of the intensity of these satellites indicates that when modeled with an atomic-kinetics code, the ionization potential depression model employed needs to produce depressions for these ions which lie between those predicted by the well known Stewart-Pyatt and Ecker-Kroll models. These results are largely consistent with recent density functional theory calculations.
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Journal articleRead J, Burdiak G, Bland SN, et al., 2024,
Point projection radiography of electromagnetically accelerated flyer plates with an external X-pinch driver (vol 95, 023508, 2024)
, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 95, ISSN: 0034-6748 -
Journal articleRead J, Burdiak G, Bland SN, et al., 2024,
Point projection radiography of electromagnetically accelerated flyer plates with an external X-pinch driver
, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 95, ISSN: 0034-6748 -
Journal articlePaddock RW, Li TS, Kim E, et al., 2024,
Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies
, Plasma Physics and Controlled Fusion, Vol: 66, ISSN: 0741-3335Low convergence ratio implosions (where wetted-foam layers are used to limit capsule convergence, achieving improved robustness to instability growth) and auxiliary heating (where electron beams are used to provide collisionless heating of a hotspot) are two promising techniques that are being explored for inertial fusion energy applications. In this paper, a new analytic study is presented to understand and predict the performance of these implosions. Firstly, conventional gain models are adapted to produce gain curves for fixed convergence ratios, which are shown to well-describe previously simulated results. Secondly, auxiliary heating is demonstrated to be well understood and interpreted through the burn-up fraction of the deuterium-tritium fuel, with the gradient of burn-up with respect to burn-averaged temperature shown to provide good qualitative predictions of the effectiveness of this technique for a given implosion. Simulations of auxiliary heating for a range of implosions are presented in support of this and demonstrate that this heating can have significant benefit for high gain implosions, being most effective when the burn-averaged temperature is between 5 and 20 keV.
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Journal articleMaler D, Belozerov O, Godinger A, et al., 2024,
Multi frame radiography of supersonic water jets interacting with a foil target
, Journal of Applied Physics, Vol: 135, ISSN: 0021-8979Pulsed-power-driven underwater electrical explosion of cylindrical or conical wire arrays produces supersonic water jets that emerge from a bath, propagating through the air above it. Interaction of these jets with solid targets may represent a new platform for attaining materials at high pressure (>1010 Pa) conditions in a university-scale laboratory. However, measurements of the internal structure of such jets and how they interact with targets are difficult optically due to large densities and density contrasts involved. We utilized multi-frame x-ray radiographic imaging capabilities of the ID19 beamline at the European Synchrotron Radiation Facility to explore the water jet and its interaction with a 50 μm thick copper foil placed a few mm from the surface of water. The jet was generated with a ∼130 kA-amplitude current pulse of ∼450 ns rise time applied to a conical wire array. X-ray imaging revealed a droplet-type structure of the jet with an average density of <400 kg/m3 propagating with a velocity of ∼1400 m/s. Measurements of deformation and subsequent perforation of the target by the jet suggested pressures at the jet–target interface of ∼5 × 109 Pa. The results were compared to hydrodynamic simulations for better understanding of the jet parameters and their interaction with the foil target. These results can be used in future research to optimize the platform, and extend it to larger jet velocities in the case of higher driving currents supplied to the wire array.
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Journal articlePachman J, Chapman DJ, Foglar M, et al., 2024,
Shock response of concrete, fibre concrete and ultrahigh performance concrete
, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 183, ISSN: 0734-743X -
Journal articleGusev AI, Lavrinovich I, Bland S, et al., 2023,
New SOS diode pumping circuit based on an all-solid-state spiral generator for high-voltage nanosecond applications
, IEEE Transactions on Plasma Science, Vol: 51, Pages: 2858-2856, ISSN: 0093-3813Semiconductor opening switch (SOS) diodes are capable to switch currents with a density of more than 1 kA/cm 2 and withstand nanosecond pulses with an amplitude of up to 1 MV. SOS diodes, however, require a specific pumping circuit that must simultaneously provide forward and reverse pumping currents with a time of ∼ 500 and ∼ 100 ns, respectively. Such a pumping circuit with energies > 1 J typically requires a gas-discharge switch or a low-efficient solid-state solution. This study proposes a novel approach to pumping SOS diodes based on a spiral generator (SG) (also known as a vector inversion generator). Due to its wave characteristics, the SG produces a bipolar current discharge that meets the time duration and current amplitude required to pump an SOS diode. Moreover, the initial pulse from the spiral typically has a relatively low current amplitude compared to the opposite polarity secondary pulse, so the SOS diode can operate at very high efficiencies. This idea has been tested using an all-solid-state SG coupled with large-area SOS diodes (1 cm 2 ). With this combination, a voltage pulse of 62 kV having a rise time of only 11 ns was obtained on an open circuit load (3 pF, 1 M Ω ). The experiments were highly repeatable, with no damage to the components despite multiple tests. There is significant scope to further improve the results, with simple alterations to the SG.
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Journal articleBailie D, White S, Irwin R, et al., 2023,
K-Edge Structure in Shock-Compressed Chlorinated Parylene
, ATOMS, Vol: 11 -
Journal articleDatta R, Angel J, Greenly JB, et al., 2023,
Plasma flows during the ablation stage of an over-massed pulsed-power-driven exploding planar wire array
, PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X- Cite
- Citations: 5
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Journal articleLee JJ, Mohammed AA, Pullen A, et al., 2023,
Mechanical characterisation of 3D printed lightweight lattice structures with varying internal design alterations
, MATERIALS TODAY COMMUNICATIONS, Vol: 36- Cite
- Citations: 6
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Journal articleHoarty DJ, Morton J, Rougier JC, et al., 2023,
Radiation burnthrough measurements to infer opacity at conditions close to the solar radiative zone–convective zone boundary
, Physics of Plasmas, Vol: 30, Pages: 1-15, ISSN: 1070-664XRecent measurements at the Sandia National Laboratory of the x-ray transmission of iron plasma have inferred opacities much higher than predicted by theory, which casts doubt on modeling of iron x-ray radiative opacity at conditions close to the solar convective zone-radiative zone boundary. An increased radiative opacity of the solar mixture, in particular iron, is a possible explanation for the disagreement in the position of the solar convection zone-radiative zone boundary as measured by helioseismology and predicted by modeling using the most recent photosphere analysis of the elemental composition. Here, we present data from radiation burnthrough experiments, which do not support a large increase in the opacity of iron at conditions close to the base of the solar convection zone and provide a constraint on the possible values of both the mean opacity and the opacity in the x-ray range of the Sandia experiments. The data agree with opacity values from current state-of-the-art opacity modeling using the CASSANDRA opacity code.
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Journal articleCrilly AJ, Niasse NPL, Fraser AR, et al., 2023,
SpK: A fast atomic and microphysics code for the high-energy-density regime
, High Energy Density Physics, Vol: 48, Pages: 1-12, ISSN: 1574-1818SpK is part of the numerical codebase at Imperial College London used to model high energy density physics (HEDP) experiments. SpK is an efficient atomic and microphysics code used to perform detailed configuration accounting calculations of electronic and ionic stage populations, opacities and emissivities for use in post-processing and radiation hydrodynamics simulations. This is done using screened hydrogenic atomic data supplemented by the NIST energy level database. An extended Saha model solves for chemical equilibrium with extensions for non-ideal physics, such as ionisation potential depression, and non thermal equilibrium corrections. A tree-heap (treap) data structure is used to store spectral data, such as opacity, which is dynamic thus allowing easy insertion of points around spectral lines without a-priori knowledge of the ion stage populations. Results from SpK are compared to other codes and descriptions of radiation transport solutions which use SpK data are given. The treap data structure and SpK’s computational efficiency allows inline post-processing of 3D hydrodynamics simulations with a dynamically evolving spectrum stored in a treap.
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Journal articleTsukada H, Nguyen T-TN, Breeze J, et al., 2023,
The risk of fragment penetrating injury to the heart
, Journal of The Mechanical Behavior of Biomedical Materials, Vol: 141, Pages: 1-6, ISSN: 1751-6161Injury due to the penetration of fragments into parts of the body has been the major cause of morbidity and mortality after an explosion. Penetrating injuries into the heart present very high mortality, yet the risk associated with such injuries has not been quantified. Quantifying this risk is key in the design of personal protection and the design of infrastructure.This study is the first quantitative assessment of cardiac penetrating injuries from energised fragments. Typical fragments (5-mm sphere, 0.78-g right-circular cylinder and 1.1-g chisel-nosed cylinder) were accelerated to a range of target striking velocities using a bespoke gas-gun system and impacted ventricular and atrial walls of lamb hearts. The severity of injury was shown to not depend on location (ventricular or atrial wall). The striking velocity with 50% probability of critical injury (Abbreviated Injury Scale (AIS) 5 score) ranged between 31 and 36 m/s across all 3 fragments used. These findings can help directly in reducing morbidity and mortality from explosive events as they can be implemented readily into models that aim to predict casualties in an explosive event, inform protocols for first responders, and improve design of infrastructure and personal protective equipment.
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Journal articleWatt RA, Rose SJ, Kettle B, et al., 2023,
Monte Carlo modeling of the linear Breit-Wheeler process within the geant4 framework
, Physical Review Accelerators and Beams, Vol: 26, Pages: 1-7, ISSN: 2469-9888A linear Breit-Wheeler module for the code geant4 has been developed. This allows signal-to-noise ratio calculations of linear Breit-Wheeler detection experiments to be performed within a single framework. The interaction between two photon sources is modeled by treating one as a static field, then photons from the second source are sampled and tracked through the field. To increase the efficiency of the module, we have used a Gaussian process regression, which can lead to an increase in the calculation rate by a factor of up to 1000. To demonstrate the capabilities of this module, we use it to perform a parameter scan, modeling an experiment based on that recently reported by Kettle et al. [New J. Phys. 23, 115006 (2021)]. We show that colliding 50-fs duration γ rays, produced through bremsstrahlung emission of a 100 pC, 2-GeV laser wakefield accelerator beam, with a 50-ps x-ray field, generated by a germanium burn-through foil heated to temperatures >150 eV, this experiment is capable of producing >1 Breit-Wheeler pair per shot.
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Journal articleStrucka J, Lukic B, Koerner M, et al., 2023,
Synchrotron radiography of Richtmyer–Meshkov instability driven by exploding wire arrays
, Physics of Fluids, Vol: 35, Pages: 1-11, ISSN: 1070-6631We present a new technique for the investigation of shock-driven hydrodynamic phenomena in gases, liquids, and solids in arbitrary geometries. The technique consists of a pulsed power-driven resistive wire array explosion in combination with multi-MHz synchrotron radiography. Compared to commonly used techniques, it offers multiple advantages: (1) the shockwave geometry can be shaped to the requirements of the experiment, (2) the pressure (P > 300 MPa) generated by the exploding wires enables the use of liquid and solid hydrodynamic targets with well-characterized initial conditions (ICs), (3) the multi-MHz radiography enables data acquisition to occur within a single experiment, eliminating uncertainties regarding repeatability of the ICs and subsequent dynamics, and (4) the radiographic measurements enable estimation of compression ratios from the x-ray attenuation. In addition, the use of a synchrotron x-ray source allows the hydrodynamic samples to be volumetrically characterized at a high spatial resolution with synchrotron-based microtomography. This experimental technique is demonstrated by performing a planar Richtmyer–Meshkov instability (RMI) experiment on an aerogel–water interface characterized by Atwood number A 0 ∼ − 0.8 and Mach number M ∼ 1.5. The qualitative and quantitative features of the experiment are discussed, including the energy deposition into the exploding wires, shockwave generation, compression of the interface, startup phase of the instability, and asymptotic growth consistent with Richtmyer's impulsive theory. Additional effects unique to liquids and solids—such as cavitation bubbles caused by rarefaction flows or initial jetting due to small perturbations—are observed. It is also demonstrated that the technique is not shape dependent by driving a cylindrically convergent RMI experiment.
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Conference paperMughal K, Bland S, Strucka J, et al., 2023,
High Speed Convergent Shockwaves Driven in Dielectrics Driven by Exploding Wires on the 14MA M3 Pulse-Powered Facility
, ISSN: 0730-9244The implosion of fast, convergent shock waves driven via the electrical explosion of cylindrical wire arrays embedded in insulator offers a highly efficient method of generating extreme pressures. At low currents (30kA) the increased density on axis was directly observed at the ESRF synchroton; at higher currents - up to 2.5MA on the Cepage generator at First Light Fusion - the implosion dynamics imply pressures >Mbar exist in warm dense plasma on axis. How this process scales to currents >5MA is unclear - a limit could exist on the speed at which the shockwaves are initially projected from the wires, set by the rate of energy deposition into the wires.
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Conference paperMundy T, Bland S, Lebedev S, et al., 2023,
Novel Experiment for Scaled Power Flow Studies Towards Next-Generation Pulsed Power
, ISSN: 2158-4915In order to develop a better understanding of current losses in the magnetically insulated region of high-power pulsed power machines, it is crucial to be able to conduct experiments at scale in smaller facilities. Here, we present a novel experiment that has been tested on the MAGPIE driver at Imperial College. The targets are inexpensive and easy to customize for experiments ranging from power flow to warm dense matter. Simulations in COMSOL indicated electric fields of up to 600 MV/m and magnetic fields of up to 300 T could be produced on MAGPIE. In initial testing, Electric fields exceeding 100 MV/m and magnetic fields exceeding 50 T were generated, and both magnetically insulated transmission and plasma-shorted transmission were demonstrated.
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Conference paperMarrow K, Mundy T, Halliday J, et al., 2023,
Radiative Instabilities in the Stagnation Layer of Colliding, X-Ray Driven Plasma Flows
, ISSN: 0730-9244We summarise existing results and future avenues of research from a novel experimental platform [1] fielded on the MAGPIE pulsed-power generator (1.4 MA, 240 ns rise time). This platform uses the x-ray pulse emitted from a wire array z-pinch to drive plasma ablation from a target. The radiatively driven outflow has a uniform (quasi-1D) structure and expands into the ambient magnetic field produced by the z-pinch.
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