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  • Conference paper
    Strucka J, Yanuka D, Theocharous S, Rososhek A, Maler D, Yao Y, Lukic B, Olbinado M, Rack A, Krasik YE, Chittenden J, Bland SNet al., 2022,

    Direct Observation of Multimode Richtmyer-Meshkov Instability Seeded by Electrothermal Instability in Dielectrically Tamped Exploding Wires

    , ISSN: 0730-9244

    We report on results from an experiment conducted at the European Synchrotron Radiation Facility Microtomography Beamline investigating the use of conductors submerged underwater and vaporised by high current densities ∼1012 A/m2 to seed plasma instabilities.

  • Journal article
    Strucka J, Halliday JWD, Gheorghiu T, Horton H, Krawczyk B, Moloney P, Parker S, Rowland G, Schwartz N, Stanislaus S, Theocharous S, Wilson C, Zhao Z, Shelkovenko TA, Pikuz SA, Bland SNet al., 2022,

    A portable X-pinch design for x-ray diagnostics of warm dense matter

    , Matter and Radiation at Extremes, Vol: 7, Pages: 1-11, ISSN: 2468-080X

    We describe the design and x-ray emission properties (temporal, spatial, and spectral) of Dry Pinch I, a portable X-pinch driver developed at Imperial College London. Dry Pinch I is a direct capacitor discharge device, 300 × 300 × 700 mm3 in size and ∼50 kg in mass, that can be used as an external driver for x-ray diagnostics in high-energy-density physics experiments. Among key findings, the device is shown to reliably produce 1.1 ± 0.3 ns long x-ray bursts that couple ∼50 mJ of energy into photon energies from 1 to 10 keV. The average shot-to-shot jitter of these bursts is found to be 10 ± 4.6 ns using a combination of x-ray and current diagnostics. The spatial extent of the x-ray hot spot from which the radiation emanates agrees with previously published results for X-pinches—suggesting a spot size of 10 ± 6 µm in the soft energy region (1–10 keV) and 190 ± 100 µm in the hard energy region (>10 keV). These characteristics mean that Dry Pinch I is ideally suited for use as a probe in experiments driven in the laboratory or at external facilities when more conventional sources of probing radiation are not available. At the same time, this is also the first detailed investigation of an X-pinch operating reliably at current rise rates of less than 1 kA/ns.

  • Conference paper
    Bott-Suzuki S, Banasek JT, Cordaro S, Bland SN, Yan J, Parker S, Chittenden Jet al., 2022,

    Developments in Long-Risetime Pulsed Power Research at UC San Diego

    , ISSN: 0730-9244

    We present construction and initial plasma experiments on a newly developed pulsed power generator at UC San Diego. The generator comprises 6 × 3.4uF capacitors in parallel which are individually switched into a simple radial feed and vacuum section. A charge voltage of 50kV means operation of the entire device can take place in air at atmospheric pressure, simplifying both construction and operation. 4-channel trigatron-style switches are triggered using a novel spiralswound transformer developed at Imperial College London. PSpice circuit models project peak currents of ∼750kA in a 1.2ms risetime, and comparisons to short circuit and load data will be presented.

  • Conference paper
    Bland SN, Theocharous S, Chittenden J, Strucka J, Yao Y, Rososhek A, Efimov S, Krasik YE, Maler D, Lukic B, Rack Aet al., 2022,

    Target Compression from Shock Waves Driven in Insulators by Wire Explosion

    , ISSN: 0730-9244

    We explore the production of highly uniform, initially planar shockwaves in water and other insulators by the pulsed power driven explosion of wire arrays. The shockwaves are then either directly interacted with small, low density spherical targets or focused via shaped reflectors onto these targets to increase the drive pressures.

  • Conference paper
    Halliday JWD, Crilly A, Chittenden J, Merlini S, Rose S, Russell D, Suttle LG, Mancini RC, Valenzuela-Villaseca V, Bland SN, Lebedev SVet al., 2022,

    An Experimental Study of Magnetic Flux Penetration in Radiatively Driven Plasma Flows

    , ISSN: 0730-9244

    In this talk we present measurements from a novel platform in which the X-Rays from a wire-array Z-Pinch irradiate a silicon target, producing an outflow of ablated silicon plasma. This ablated plasma expands into ambient, dynamically significant magnetic fields (B ∼ 5 T) which are supported by the current flowing through the Z-Pinch.

  • Conference paper
    Fox MFJ, Bland S, Mangles SPD, McGinty Jet al., 2022,

    Expectations of how student views on experimental physics develop during an undergraduate degree

    , Physics Education Research Conference (PERC), Publisher: AMER ASSOC PHYSICS TEACHERS, Pages: 182-187, ISSN: 2377-2379
  • Journal article
    Halliday JWD, Bland SN, Hare JD, Parker S, Suttle LG, Russell DR, Lebedev SVet al., 2021,

    A time-resolved imaging system for the diagnosis of x-ray self-emission in high energy density physics experiments

    , Review of Scientific Instruments, Vol: 92, Pages: 123507-123507, ISSN: 0034-6748

    A diagnostic capable of recording spatially and temporally resolved x-ray self-emission data was developed to characterize experiments on the MAGPIE pulsed-power generator. The diagnostic used two separate imaging systems: a pinhole imaging system with two-dimensional spatial resolution and a slit imaging system with one-dimensional spatial resolution. The two-dimensional imaging system imaged light onto the image plate. The one-dimensional imaging system imaged light onto the same piece of image plate and a linear array of silicon photodiodes. This design allowed the cross-comparison of different images, allowing a picture of the spatial and temporal distribution of x-ray self-emission to be established. The design was tested in a series of pulsed-power-driven magnetic-reconnection experiments.

  • Journal article
    Tilikin IN, Shelkovenko TA, Pikuz SA, Bland SNet al., 2021,

    Multiframe point-projection radiography imaging based on hybrid X-pinch

    , Review of Scientific Instruments, Vol: 92, Pages: 1-5, ISSN: 0034-6748

    This paper demonstrates the possibility of using a new configuration of the hybrid X-pinch to produce a set of spatially and temporarily separate x-ray bursts that could be used for the radiography of dynamic events. To achieve this, a longer than normal wire is placed between the conical electrodes of the hybrid X-pinch, and a set of small spacers (fishing weights) is placed along the wire. Each subsection of the wire then acts as a unique X-pinch, producing its own radiation burst from a small (∼3 µm) spot. The timing between bursts is 20–50 ns, and each is <2 ns in duration. For comparison, if a longer wire is simply employed without spacers, hotspots of radiation occur in random positions and the time between any two bursts does not exceed 20 ns. Examples of two and three frame point-projection radiography of solid-state and plasma test objects are given.

  • Journal article
    Kettle B, Hollatz D, Gerstmayr E, Samarin GM, Alejo A, Astbury S, Baird C, Bohlen S, Campbell M, Colgan C, Dannheim D, Gregory C, Harsh H, Hatfield P, Hinojosa J, Katzir Y, Morton J, Murphy CD, Nurnberg A, Osterhoff J, Perez-Callejo G, Poder K, Rajeev PP, Roedel C, Roeder F, Salgado FC, Sarri G, Seidel A, Spannagel S, Spindloe C, Steinke S, Streeter MJ, Thomas AGR, Underwood C, Watt R, Zepf M, Rose SJ, Mangles SPDet al., 2021,

    A laser-plasma platform for photon-photon physics: the two photon Breit-Wheeler process

    , New Journal of Physics, Vol: 23, ISSN: 1367-2630

    We describe a laser–plasma platform for photon–photon collision experiments to measure fundamental quantum electrodynamic processes. As an example we describe using this platform to attempt to observe the linear Breit–Wheeler process. The platform has been developed using the Gemini laser facility at the Rutherford Appleton Laboratory. A laser Wakefield accelerator and a bremsstrahlung convertor are used to generate a collimated beam of photons with energies of hundreds of MeV, that collide with keV x-ray photons generated by a laser heated plasma target. To detect the pairs generated by the photon–photon collisions, a magnetic transport system has been developed which directs the pairs onto scintillation-based and hybrid silicon pixel single particle detectors (SPDs). We present commissioning results from an experimental campaign using this laser–plasma platform for photon–photon physics, demonstrating successful generation of both photon sources, characterisation of the magnetic transport system and calibration of the SPDs, and discuss the feasibility of this platform for the observation of the Breit–Wheeler process. The design of the platform will also serve as the basis for the investigation of strong-field quantum electrodynamic processes such as the nonlinear Breit–Wheeler and the Trident process, or eventually, photon–photon scattering.

  • Conference paper
    Baggott RA, Rose SJ, Mangles SPD, 2021,

    Temperature Equilibration Due to Charge State Fluctuations in Dense Plasmas

    , ISSN: 0730-9244

    The charge states of ions in dense plasmas fluctuate due to collisional ionization and recombination. In this work we show how, by modifying the ion interaction potential, these fluctuations can mediate energy exchange between the plasma electrons and ions. We also develop a theoretical framework for this novel electron-ion energy transfer mechanism.

  • Journal article
    Yan J, Parker S, Bland S, 2021,

    An investigation into high-voltage spiral generators utilizing thyristor input switches

    , IEEE Transactions on Power Electronics, Vol: 36, Pages: 10005-10019, ISSN: 0885-8993

    High-voltage nanosecond pulses are widely used in scientific research, but their wider adoption in industry requires compact, cost-effective, and easy to use generators to be developed. This article presents the modeling and experimental investigations into one method of producing such pulses-a spiral generator with a solid-state-thyristor-based input switch. It includes how the pulses are formed within the spiral, why a high-speed input switch is required, and how the geometry of the spiral dictates its output characteristics and the effects of different loads. Using thyristors, often connected in series to increase the operating voltage of the spiral, enables the spiral generators to have low jitter, high repetition rate, and long lifetime. Modeling of the circuit used a combination of telegraph equations to account for the wave propagation along the spiral and a lumped circuit exchanging charge between the spiral and the input switch and load. The model is verified by the detailed experimental results with the relative error being <; 10% in most cases. The output voltage pulse was often observed to have an initial peak of much lower magnitude than the subsequent peak(s)-which can only be fully explained by considering wave propagation effects. Lower input switch inductance, shorter switching time, larger mean diameter of the spiral, and increasing the width of the copper tape that makes up the spiral can all increase the voltage multiplication efficiency. Although increasing the number of turns that makes up the spiral can increase the output voltage, it can also lower the multiplication efficiency. By understanding the effects of different geometries, the spiral can be optimized to drive different loads-three applications of such spiral generators are then presented-pulses with 10 kV amplitude and 10 kHz repetition rate for driving dielectric barrier discharge plasma, pulses with amplitude of 10 kV and 10 kV/ns rising rate for triggering of advanced solid-sta

  • Journal article
    Rose SJ, Hatfield PW, 2021,

    Astronomy Domine: advancing science with a burning plasma

    , Contemporary Physics, Vol: 62, Pages: 14-23, ISSN: 0010-7514

    Inertial Confinement Fusion (ICF) is a subject that has been studied for decades, because of its potential for clean energy generation. Although thermonuclear fusion has been achieved, the energy out has always been considerably less than the energy in, so high energy gain with a burning thermonuclear plasma is still some way off. A multitude of new science has come from the ICF programme that is relevant outside the field (typically in astrophysics). What we look at in this text is what new science can come from the much more extreme conditions that would be created in the laboratory if a burning ICF plasma could be created -- in terms of energy density the most extreme macroscopic environment ever created. We show that this could impact science from particle physics through astrophysics and on to cosmology. We also believe that the experiments that we propose here are only a small part of the science that will be opened up when a burning thermonuclear plasma is created in the laboratory.

  • Journal article
    Baggott RA, Rose S, Mangles SPD, 2021,

    Temperature equilibration due to charge state fluctuations in dense plasmas

    , Physical Review Letters, Vol: 27, ISSN: 0031-9007

    The charge states of ions in dense plasmas fluctuate due to collisionalionization and recombination. Here we show how, by modifying the ioninteraction potential, these fluctuations can mediate energy exchange betweenthe plasma electrons and ions. Moreover, we develop a theory for this novelelectron-ion energy transfer mechanism. Calculations using a random walkapproach for the fluctuations suggest that the energy exchange rate from chargestate fluctuations could be comparable to direct electron-ion collisions. Thismechanism is, however, predicted to exhibit a complex dependence on thetemperature and ionization state of the plasma, which could contribute to ourunderstanding of significant variation in experimental measurements ofequilibration times.

  • Journal article
    Spencer Kelly R, Hart LJF, Rose SJ, 2021,

    An investigation of efficient muon production for use in muon catalyzed fusion

    , Journal of Physics: Energy, Vol: 3, Pages: 1-7, ISSN: 2515-7655

    We model the energy cost of producing muons for use in muon catalyzed fusion and show that by careful design the cost can be reduced by a factor of 2.5 below current values. This is done by recapturing the kinetic energy of waste particles and generating heat through tritium breeding. When put together with the modeling of muon catalyzed fusion we estimate that electrical output/electrical input of 14% can be achieved currently.

  • Journal article
    Maler D, Efimov S, Rososhek A, Bland SN, Krasik YEet al., 2021,

    Generation of supersonic jets from underwater electrical explosions of wire arrays

    , PHYSICS OF PLASMAS, Vol: 28, ISSN: 1070-664X
  • Journal article
    Hatfield PW, Gaffney JA, Anderson GJ, Ali S, Antonelli L, Başeğmez du Pree S, Citrin J, Fajardo M, Knapp P, Kettle B, Kustowski B, MacDonald MJ, Mariscal D, Martin ME, Nagayama T, Palmer CAJ, Peterson JL, Rose S, Ruby JJ, Shneider C, Streeter MJV, Trickey W, Williams Bet al., 2021,

    The data-driven future of high-energy-density physics

    , Nature, Vol: 593, Pages: 351-361, ISSN: 0028-0836

    High-energy-density physics is the field of physics concerned with studying matter at extremely high temperatures and densities. Such conditions produce highly nonlinear plasmas, in which several phenomena that can normally be treated independently of one another become strongly coupled. The study of these plasmas is important for our understanding of astrophysics, nuclear fusion and fundamental physics—however, the nonlinearities and strong couplings present in these extreme physical systems makes them very difficult to understand theoretically or to optimize experimentally. Here we argue that machine learning models and data-driven methods are in the process of reshaping our exploration of these extreme systems that have hitherto proved far too nonlinear for human researchers. From a fundamental perspective, our understanding can be improved by the way in which machine learning models can rapidly discover complex interactions in large datasets. From a practical point of view, the newest generation of extreme physics facilities can perform experiments multiple times a second (as opposed to approximately daily), thus moving away from human-based control towards automatic control based on real-time interpretation of diagnostic data and updates of the physics model. To make the most of these emerging opportunities, we suggest proposals for the community in terms of research design, training, best practice and support for synthetic diagnostics and data analysis.

  • Journal article
    Rankin I, Nguyen T, McMenemy L, Clasper J, Masouros Set al., 2021,

    The injury mechanism of traumatic amputation

    , Frontiers in Bioengineering and Biotechnology, Vol: 9, ISSN: 2296-4185

    Traumatic amputation has been one of the most defining injuries associated with explosive devices. An understanding of the mechanism of injury is essential in order to reduce its incidence and devastating consequences to the individual and their support network. In this study, traumatic amputation is reproduced using high-velocity environmental debris in an animal cadaveric model. The study findings are combined with previous work to describe fully the mechanism of injury as follows. The shock wave impacts with the casualty, followed by energised projectiles (environmental debris or fragmentation) carried by the blast. These cause skin and soft tissue injury, followed by skeletal trauma which compounds to produce segmental and multifragmental fractures. A critical injury point is reached, whereby the underlying integrity of both skeletal and soft tissues of the limb has been compromised. The blast wind that follows these energised projectiles completes the amputation at the level of the disruption, and traumatic amputation occurs. These findings produce a shift in the understanding of traumatic amputation due to blast from a mechanism predominately thought mediated by primary and tertiary blast, to now include secondary blast mechanisms, and inform change for mitigative strategies.

  • Journal article
    Yan J, Parker S, Gheorghiu T, Schwartz N, Theocharous S, Bland SNet al., 2021,

    Miniature solid-state switched spiral generator for the cost effective, programmable triggering of large scale pulsed power accelerators

    , Physical Review Accelerators and Beams, Vol: 24, Pages: 1-10, ISSN: 2469-9888

    This paper presents the design and testing of several different configurations of spiral generator, designed to trigger high current switches in the next generation of pulsed power devices. In particular, it details the development of spiral generators that utilize new ultrafast thyristor technology as an input switch, along with a polarity dependent output gap to improve the efficiency of the spiral generator design. The generator produced 50 kV from a 3.6 kV charging voltage, with a rise time of only 50 ns and a jitter of 1.3 ns—directly comparable, if not better than, a generator employing a triggered spark gap as the input switch. The output gap was constructed in house from commonly available components and a 3D printed case, and showed remarkable repeatability and stability—simple alterations to the output gap could further reduce the rise time. The entire spiral generator, along with control and charging electronics, fitted into a case only 210×145×33  mm.

  • Journal article
    Perez-Callejo G, Marley E, Liedahl DA, Jarrott LC, Kemp GE, Heeter RF, Emig JA, Foord ME, Schneider MB, Rose SJ, Wark JSet al., 2021,

    Demonstration of geometric effects and resonant scattering in the X-Ray spectra of high-energy-density plasmas

    , Physical Review Letters, Vol: 126, Pages: 1-7, ISSN: 0031-9007

    In a plasma of sufficient size and density, photons emitted within the system have a probability of being reabsorbed and reemitted multiple times—a phenomenon known in astrophysics as resonant scattering. This effect alters the ratio of optically thick to optically thin lines, depending on the plasma geometry and viewing angle, and has significant implications for the spectra observed in a number of astrophysical scenarios, but has not previously been studied in a controlled laboratory plasma. We demonstrate the effect in the x-ray spectra emitted by cylindrical plasmas generated by high power laser irradiation, and the results confirm the geometrical interpretation of resonant scattering.

  • Journal article
    Rankin IA, Thuy-Tien N, Carpanen D, Darwood A, Clasper JC, Masouros SDet al., 2021,

    Pelvic protection limiting lower limb flail reduces mortality

    , Journal of Biomechanical Engineering, Vol: 143, ISSN: 0148-0731

    Pelvic blast injury is one of the most severe patterns of injury to be sustained by casualties of explosions. We have previously identified the mechanism of injury in a shock tube-mediated murine model, linking outward flail of the lower limbs to unstable pelvic fractures and vascular injury. As current military pelvic protection does not protect against lower limb flail, in this study we have utilized the same murine model to investigate the potential of novel pelvic protection to reduce injury severity. Fifty cadaveric mice underwent shock-tube blast testing and subsequent injury analysis. Pelvic protection limiting lower limb flail resulted in a reduction of pelvic fracture incidence from both front-on (relative risk (RR) 0.5, 95% confidence intervals (CIs) 0.3–0.9, p < 0.01) and under-body (RR 0.3, 95% CI 0.1–0.8 p < 0.01) blast, with elimination of vascular injury in both groups (p < 0.001). In contrast, pelvic protection, which did not limit flail, had no effect on fracture incidence compared to the control group and was only associated with a minimal reduction in vascular injury (RR 0.6, 95% CI 0.4–1.0, p < 0.05). This study has utilized a novel strategy to provide proof of concept for the use of pelvic protection, which limits limb flail to mitigate the effects of pelvic blast injury.

  • Journal article
    Rose S, Hatfield P, Scott R, 2020,

    Modelling burning thermonuclear plasma

    , Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 378, Pages: 1-8, ISSN: 1364-503X

    Considerable progress towards the achievement ofthermonuclear burn using inertial confinement fusion has beenachieved at the National Ignition Facility (NIF) in the USA inthe last few years. Other drivers, such as the Z-machine atSandia, are also making progress towards this goal. A burningthermonuclear plasma would provide a unique and extremeplasma environment; in this paper we discuss a) differenttheoretical challenges involved in modelling burning plasmasnot currently considered, b) the use of novel machine learningbased methods that might help large facilities reach ignition,and c) the connections that a burning plasma might have tofundamental physics, including QED studies, and the replicationand exploration of conditions that last occurred in the first fewminutes after the Big Bang.

  • Journal article
    Pérez-Callejo G, Jarrott LC, Liedahl DA, Schneider MB, Wark JS, Rose SJet al., 2020,

    Measuring the oscillator strength of intercombination lines of helium-like V ions in a laser-produced-plasma

    , Journal of Quantitative Spectroscopy and Radiative Transfer, Vol: 256, ISSN: 0022-4073

    We present results of measurements of the oscillator strength of intercombination lines of He-like Vanadium ions in high energy density (HED) laser-produced-plasmas and compare them with the simulations from commonly used codes and data from the NIST database. Whilst not yet sufficiently accurate to constrain different trusted atomic-physics models for the particular system studied, our results are in agreement with the available data within experimental error bars, yet differ from cruder approximations of the oscillator strength used in certain atomic-kinetics packages, suggesting that this general method could be further extended to be used as a measurement of the oscillator strength of additional atomic transitions under the extreme conditions that are achieved in HED experiments.

  • Journal article
    Pérez-Callejo G, Barrios MA, Liedahl DA, Schneider MB, Jones O, Landen O, Kauffman RL, Suter LJ, Moody JD, Rose SJ, Wark JSet al., 2020,

    A novel method to measure ion density in ICF experiments using x-ray spectroscopy of cylindrical tracers

    , Physics of Plasmas, Vol: 27, Pages: 112714-1-112714-11, ISSN: 1070-664X

    The indirect drive approach to inertial confinement fusion has undergone important advances in the past few years. Improvements in temperature and density diagnostic methods are leading to more accurate measurements of the plasma conditions inside the Hohlraum and therefore to more efficient experimental designs. The implementation of dot spectroscopy has proven to be a versatile approach to extracting space- and time-dependent electron temperatures. In this method, a microdot of a mid-Z material is placed inside the Hohlraum and its K-shell emission spectrum is used to determine the plasma temperature. However, radiation transport of optically thick lines acting within the cylindrical dot geometry influences the outgoing spectral distribution in a manner that depends on the viewing angle. This angular dependence has recently been studied in the high energy density regime at the OMEGA laser facility, which allowed us to design and benchmark appropriate radiative transfer models that can replicate these geometric effects. By combining these models with the measurements from the dot spectroscopy experiments at the National Ignition Facility, we demonstrate here a novel technique that exploits the transport effects to obtain time-resolved measurements of the ion density of the tracer dots, without the need for additional diagnostics. We find excellent agreement between experiment and simulation, opening the possibility of using these geometric effects as a density diagnostic in future experiments.

  • Conference paper
    White S, Irwin R, Warwick R, Sarri G, Gribakin GF, Keenan FP, Hill E, Rose S, Ferland GJ, Wang F, Zhao G, Han B, Riley Det al., 2020,

    Generation of photoionized plasmas in the laboratory: Analogues to astrophysical sources

    , Laboratory Astrophysics fFrom Observation to Interpretation, Publisher: Cambridge University Press, Pages: 321-325, ISSN: 1743-9213

    Implementation of a novel experimental approach using a bright source of narrowband x-ray emission has enabled the production of a photoionized argon plasma of relevance to astrophysical modelling codes such as Cloudy. We present results showing that the photoionization parameter ζ = 4πF/ne generated using the VULCAN laser was ≈ 50 erg cm s−1, higher than those obtained previously with more powerful facilities. Comparison of our argon emission-line spectra in the 4.15 - 4.25 Å range at varying initial gas pressures with predictions from the Cloudy code and a simple time-dependent code are also presented. Finally we briefly discuss how this proof-of-principle experiment may be scaled to larger facilities such as ORION to produce the closest laboratory analogue to a photoionized plasma.

  • Journal article
    Baggott R, Rose S, Mangles S, 2020,

    Calculating opacity in hot, dense matter using second-order electron-photon and two-photon transitions to approximate line broadening

    , Physical Review Letters, Vol: 125, Pages: 145002 – 1-145002 – 5, ISSN: 0031-9007

    Calculations of the opacity of hot, dense matter require models for plasma line broadening. How-ever, the most general theories are too complex to calculate directly and some approximation is inevitably required. The most widely-used approaches focus on the line centre, where a Lorentzian shape is obtained. Here, we demonstrate that in the opposite limit, far from the line centre, the opacity can be expressed in terms of second-order transitions, such as electron-photon and two-photon processes. We suggest that this insight could form the basis for a new approach to improve calculations of opacity in hot, dense matter. Preliminary calculations suggest that this approach could yield increased opacity away from absorption lines.

  • Journal article
    Yanuka D, Theocharous S, Chittenden JP, Bland SNet al., 2020,

    High velocity outflows along the axis of pulsed power driven rod z-pinches

    , AIP Advances, Vol: 10, Pages: 1-9, ISSN: 2158-3226

    We report on initial observations of high velocity outflows from the ends of a rod compressed using pulsed power. 1 mm and 2 mm diameter copper rods were placed in a water bath and driven by ∼0.6 MA currents with rise times of ∼700 ns. Laser backlit framing images and streak photography showed an outflow of the material from the ends of each rod, of the initial velocity of up to 7 km/s, which began ∼500 ns after the start of the current pulse and continued throughout the experiment. Ballistics gel was used to help separate low density gas/plasma from any solid/liquid component in the outflow, successfully capturing the material from larger diameter rods (enabling an estimate of its energy) and tracing the path of the material that passed straight through the gel with smaller rods. Experimental results were compared to 1D and 2D MHD simulations performed with the Gorgon code. These suggested that the outflow had two different components, resulting from two different physical processes. Differences in the resistivity between the copper rod and stainless steel anode result in the opening of a small gap between them and ablated stainless steel being projected above the rod, which is captured in framing and streak images. Later in time, a dense copper material, pinched by the magnetic pressure, is launched—explaining the ballistics gel results. The simulations also suggest that the tamped explosion of the rod surface plays a small role in any outflow.

  • Journal article
    Sory DR, Amin HD, Chapman D, Proud WG, Rankin SMet al., 2020,

    Replicating landmine blast loading in cellular <i>in Vitro</i> models

    , Physical Biology, Vol: 17, ISSN: 1478-3967

    Trauma arising from landmines and improvised explosive devices promotes heterotopic ossification, the formation of extra-skeletal bone in non-osseous tissue. To date, experimental platforms that can replicate the loading parameter space relevant to improvised explosive device and landmine blast wave exposure have not been available to study the effects of such non-physiological mechanical loading on cells. Here, we present the design and calibration of three distinct in vitro experimental loading platforms that allow us to replicate the spectrum of loading conditions recorded in near-field blast wave exposure. We subjected cells in suspension or in a three-dimensional hydrogel to strain rates up to 6000 s-1and pressure levels up to 45 MPa. Our results highlight that cellular activation is regulated in a non-linear fashion - not by a single mechanical parameter, it is the combined action of the applied mechanical pressure, rate of loading and loading impulse, along with the extracellular environment used to convey the pressure waves. Finally, our research indicates that PO MSCs are finely tuned to respond to mechanical stimuli that fall within defined ranges of loading.

  • Journal article
    Nguyen TT, Carpanen D, Rankin I, Ramasamy A, Breeze J, Proud W, Clasper J, Masouros Set al., 2020,

    Mapping the risk of fracture of the tibia from penetrating fragments

    , Frontiers in Bioengineering and Biotechnology, Vol: 8, Pages: 1-11, ISSN: 2296-4185

    Penetrating injuries are commonly inflicted in attacks with explosive devices. The extremities, and especially the leg, are the most commonly affected body areas, presenting high risk of infection, slow recovery, and threat of amputation. The aim of this study was to quantify the risk of fracture to the anteromedial, posterior, and lateral aspects of the tibia from a metal fragment-simulating projectile (FSP). A gas gun system and a 0.78-g cylindrical FSP were employed to perform tests on an ovine tibia model. The results from the animal study were subsequently scaled to obtain fracture-risk curves for the human tibia using the cortical thickness ratio. The thickness of the surrounding soft tissue was also taken into account when assessing fracture risk. The lateral cortex of the tibia was found to be most susceptible tofracture,whose impact velocity at 50% risk of EF1+, EF2+, EF3+, and EF4+ fracture types –according to the modified Winquist-Hansen classification –were 174, 190, 212,and 282 m/s respectively. The findings of this study will be used to increase the fidelity of predictive models of projectile penetration.

  • Journal article
    Rankin I, Nguyen TT, Carpanen D, Clasper J, Masouros Set al., 2020,

    A new understanding of the mechanism of injury to the pelvis and lower limbs in blast

    , Frontiers in Bioengineering and Biotechnology, Vol: 8, ISSN: 2296-4185

    Dismounted complex blast injury (DCBI) has been one of the most severe forms of trauma sustained in recent conflicts. This injury has been partially attributed to limb flail; however, the full causative mechanism has not yet been fully determined. Soil ejecta has been hypothesized as a significant contributor to the injury but remains untested. In this study, a small-animal model of gas-gun mediated high velocity sand blast was used to investigate this mechanism. The results demonstrated a correlation between increasing sand blast velocity and injury patterns of worsening severity across the trauma range. This study is the first to replicate high velocity sand blast and the first model to reproduce the pattern of injury seen in DCBI. These findings are consistent with clinical and battlefield data. They represent a significant change in the understanding of blast injury, producing a new mechanistic theory of traumatic amputation. This mechanism of traumatic amputation is shown to be high velocity sand blast causing the initial tissue disruption, with the following blast wind and resultant limb flail completing the amputation. These findings implicate high velocity sand blast, in addition to limb flail, as a critical mechanism of injury in the dismounted blast casualty.

  • Journal article
    Millett JCF, Avraam P, Whiteman G, Chapman DJ, Case Set al., 2020,

    The role of orientation on the shock response of single crystal tantalum

    , JOURNAL OF APPLIED PHYSICS, Vol: 128, ISSN: 0021-8979

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