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  • Journal article
    Read J, Burdiak G, Bland SN, Caballero Bendixsen LS, Paxton-Fear L, Niasse N, Dobranszki C, Hawker Net al., 2024,

    Point projection radiography of electromagnetically accelerated flyer plates with an external X-pinch driver.

    , Rev Sci Instrum, Vol: 95

    A platform for flyer plate benchmarking experiments has been developed, with an external X-pinch driver for point projection radiography. The experiments were performed using CEPAGE, a low inductance pulsed power machine at First Light Fusion (2 MA, 1.4 µs), with a new vacuum transmission line and flyer load hardware designed specifically to give a line of sight for radiography. A broadband 10-20 keV x-ray source was produced by a portable X-pinch driver (140 kA, 350 ns) [Strucka et al., Matter Radiat. Extremes 7, 016901 (2021)] and was used to image the flyer. Radiography compliments the pre-existing diagnostic suite, which consists of current probes, velocimetry, and side-on optical probing of the impact shock transmitted into a transparent sample. The platform allows for significant insights into the 2D and 3D nature of the flyer launch, such as deformation and instability formation. It was used to diagnose a 10 × 9 × 1 mm3 aluminum flyer, which reached a peak velocity of 4.2 km s-1 before impact with a poly(methylmethacrylate) sample. The experimental configuration, on-shot source characterization, and the results from two flyer plate experiments on CEPAGE are discussed.

  • Journal article
    Paddock RW, Li TS, Kim E, Lee JJ, Martin H, Ruskov RT, Hughes S, Rose SJ, Murphy CD, H Scott RH, Bingham R, Garbett W, Elisseev VV, Haines BM, Zylstra AB, Campbell EM, Thomas CA, Goffrey T, Arber TD, Aboushelbaya R, Von der Leyen MW, W Wang RH, James AA, Ouatu I, Timmis R, Howard S, Atonga E, Norreys PAet al., 2024,

    Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies

    , Plasma Physics and Controlled Fusion, Vol: 66, ISSN: 0741-3335

    Low 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.

  • Journal article
    Maler D, Belozerov O, Godinger A, Efimov S, Strucka J, Yao Y, Mughal K, Lukic B, Rack A, Bland SN, Krasik YEet al., 2024,

    Multi frame radiography of supersonic water jets interacting with a foil target

    , Journal of Applied Physics, Vol: 135, ISSN: 0021-8979

    Pulsed-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.

  • Journal article
    Gusev AI, Lavrinovich I, Bland S, de Ferron AS, Pecastaing L, Parker S, Yan J, Novac BMet 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: 0093-3813

    Semiconductor 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.

  • Journal article
    Bailie D, White S, Irwin R, Hyland C, Warwick R, Kettle B, Breslin N, Bland SN, Chapman DJ, Mangles SPD, Baggot RA, Tubman ER, Riley Det al., 2023,

    K-Edge Structure in Shock-Compressed Chlorinated Parylene

    , ATOMS, Vol: 11
  • Journal article
    Datta R, Angel J, Greenly JB, Bland SN, Chittenden JP, Lavine ES, Potter WM, Robinson D, Varnish TWO, Wong E, Hammer DA, Kusse BR, Hare JDet 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
  • Journal article
    Hoarty DJ, Morton J, Rougier JC, Rubery M, Opachich YP, Swatton D, Richardson S, Heeter RF, McLean K, Rose SJ, Perry TS, Remington Bet 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: 1070-664X

    Recent 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.

  • Journal article
    Crilly AJ, Niasse NPL, Fraser AR, Chapman DA, McLean KW, Rose SJ, Chittenden JPet 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: 1574-1818

    SpK 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.

  • Journal article
    Watt RA, Rose SJ, Kettle B, Mangles SPDet 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: 2469-9888

    A 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.

  • Journal article
    Strucka J, Lukic B, Koerner M, Halliday JWD, Yao Y, Mughal K, Maler D, Efimov S, Skidmore J, Rack A, Krasik Y, Chittenden J, Bland SNet al., 2023,

    Synchrotron radiography of Richtmyer–Meshkov instability driven by exploding wire arrays

    , Physics of Fluids, Vol: 35, Pages: 1-11, ISSN: 1070-6631

    We 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.

  • Conference paper
    Mundy T, Bland S, Lebedev S, Chittenden J, Marrow K, Suttle L, Halliday J, Rose Cet al., 2023,

    Novel Experiment for Scaled Power Flow Studies Towards Next-Generation Pulsed Power

    , ISSN: 2158-4915

    In 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.

  • Journal article
    Breach O, Hatfield P, Rose S, 2022,

    Optimising point source irradiation of a capsule for maximum uniformity

    , High Energy Density Physics, Vol: 45, Pages: 1-7, ISSN: 1574-1818

    Inertial Confinement Fusion involves the implosion of a spherical capsule con-taining thermonuclear fuel. The implosion is driven by irradiating the outsideof the capsule by X-rays or by optical laser irradiation, where in each casethe highest uniformity of irradiation is sought. In this paper we consider thetheoretical problem of irradiation of a capsule by point sources of X-rays, andconfigurations which maximize uniformity are sought. By studying the root-mean-square deviation in terms of different order harmonic modes, we ratio-nalise the dependence of uniformity on distance d of the point sources fromthe centre of a capsule. After investigating simple configurations based onthe Platonic solids, we use a global optimisation algorithm (basin-hopping)to seek better arrangements. The optimum configurations are found to de-pend strongly on d; at certain values which minimise nonuniformity, theseinvolve grouping of sources on the vertices of octahedra or icosahedra, whichwe explain using a modal decomposition. The effect of uncertainties in bothposition and intensity is studied, and lastly we investigate the illuminationof a capsule whose radius is changing with time.

  • Journal article
    Lavrinovich I, Gusev AI, Bland S, de Ferron AS, Pecastaing L, Parker S, Yan J, Novac BMet al., 2022,

    2-kV thyristor triggered in impact-ionization wave mode by a solid-state spiral generator

    , IEEE Transactions on Plasma Science, Vol: 50, Pages: 3443-3451, ISSN: 0093-3813

    Impact-ionization wave triggering of a thyristor enables it to switch significantly higher currents with much faster rise times ( dI/dt ) than through conventional triggering; indeed tests on commercial components demonstrate that both current and dI/dt can be increased an order of magnitude over their specified datasheet values by utilizing impact ionization. However, creating an impact ionization wave places stringent requirements on the generator used to trigger the thyristor—particularly the trigger pulse must have a voltage rise rate ( dV/dt ) of more than 1 kV/ns and an amplitude over twice the thyristors static breakdown voltage. Given the capacitance of a thyristor is relatively large, often hundreds of pF, this is difficult to achieve with many common triggering methods. In this study, we present a bespoke, cost-effective, trigger generator that has been developed based on spiral/vector inversion techniques coupled to an optimized sharpening circuit. Using this generator, both a 2-kV single thyristor and a 4-kV stack of two thyristors in series were triggered in the impact-ionization mode. The thyristors had a wafer diameter of 32 mm and capacitances of 370 pF. With a single thyristor 100 shots were performed with it switching a peak current of 1.25 kA and an associated dI/dt of 12 kA/ μs . With two thyristors, peak currents of 2.6 kA and with dI/dt of 25 kA/ μs were achieved. In all experiments no degradation of the semiconductor structure was observed. The work opens the way for developing very powerful, but still compact, solid-state trigger generators and larger pulsers for a wide range of pulsed power applications.

  • Journal article
    Beesley JJ, Rose SJ, 2022,

    High-temperature limit of Breit-Wheeler pair production in a black-body field

    , Results in Physics, Vol: 41, Pages: 1-3, ISSN: 2211-3797

    This paper presents an analytic expression for the high-temperature limit of Breit-Wheeler pair production in a black-body field to lowest order in perturbation theory, of interest in early-universe cosmology. The limit is found to be a good approximation for temperatures above about three times the electron rest energy. It is also found that coupling to low-energy processes remains important at arbitrarily high temperatures, due to the exchange of a low-energy virtual fermion near the mass shell. This appears mathematically in the rate as a logarithmic factor of the photon temperature divided by the electron rest mass.

  • Journal article
    Singh RL, White S, Charlwood M, Keenan FP, Hyland C, Bailie D, Audet T, Sarri G, Rose SJ, Morton J, Baird C, Spindloe C, Riley Det al., 2022,

    L-shell X-Ray conversion yields for laser-irradiated tin and silver foils

    , Laser and Particle Beams, Vol: 2022, Pages: 1-10, ISSN: 0263-0346

    We have employed the VULCAN laser facility to generate a laser plasma X-ray source for use in photoionization experiments. A nanosecond laser pulse with an intensity of order 1015 Wcm−2 was used to irradiate thin Ag or Sn foil targets coated onto a parylene substrate, and the L-shell emission in the 3.3–4.4 keV range was recorded for both the laser-irradiated and nonirradiated sides. Both the experimental and simulation results show higher laser to X-ray conversion yields for Ag compared with Sn, with our simulations indicating yields approximately a factor of two higher than those found in the experiments. Although detailed angular data were not available experimentally, the simulations indicate that the emission is quite isotropic on the laser-irradiated side but shows close to a cosine variation on the nonirradiated side of the target as seen experimentally in the previous work.

  • Journal article
    Maler D, Efimov S, Liverts M, Theocharous S, Strucka J, Yao Y, Proud W, Rack A, Lukic B, Bland SN, Krasik YEet al., 2022,

    Peculiarities of planar shockwave interaction with air-water interface and solid target

    , PHYSICS OF PLASMAS, Vol: 29, ISSN: 1070-664X
  • Journal article
    Halliday JWD, Crilly A, Chittenden J, Mancini RC, Merlini S, Rose S, Russell DR, Suttle LG, Valenzuela-Villaseca V, Bland SN, Lebedev SVet al., 2022,

    Investigating radiatively driven, magnetized plasmas with a university scale pulsed-power generator

    , Physics of Plasmas, Vol: 29, Pages: 1-13, ISSN: 1070-664X

    We present first results from a novel experimental platform which is able toaccess physics relevant to topics including indirect-drive magnetised ICF;laser energy deposition; various topics in atomic physics; and laboratoryastrophysics (for example the penetration of B-fields into HED plasmas). Thisplatform uses the X-Rays from a wire array Z-Pinch to irradiate a silicontarget, producing an outflow of ablated plasma. The ablated plasma expands intoambient, dynamically significant B-fields (~5 T) which are supported by thecurrent flowing through the Z-Pinch. The outflows have a well-defined(quasi-1D) morphology, enabling the study of fundamental processes typicallyonly available in more complex, integrated schemes. Experiments were fielded onthe MAGPIE pulsed-power generator (1.4 MA, 240 ns rise time). On this machine awire array Z-Pinch produces an X-Ray pulse carrying a total energy of ~15 kJover ~30 ns. This equates to an average brightness temperature of around 10 eVon-target.

  • Journal article
    McLean KW, Rose SJ, 2022,

    Multi-group radiation diffusion convergence in low-density foam experiments

    , Journal of Quantitative Spectroscopy and Radiative Transfer, Vol: 280, Pages: 1-13, ISSN: 0022-4073

    We present an in-depth analysis of a Marshak radiation wave moving through an iron-oxide (Fe2O3) foamusing a 1D multigroup diffusive radiation transport model, MDART (Multigroup Diffusion Algorithm forRadiation Transport). We consider the consequences of under-resolving the group structure and addresshow this could lead to incorrect conclusions in the analysis of general supersonic radiation wave experiments. We also provide an analysis of the types of experimental outcome one may incorrectly link tophysical effects but are in fact due to poor simulation practice.

  • Journal article
    Nguyen TT, Breeze J, Masouros S, 2022,

    Penetration of Energised Metal Fragments to Porcine Thoracic Tissues

    , Journal of Biomechanical Engineering, ISSN: 0148-0731

    Energised fragments from explosive devices have been the most common mechanism of injury to both military personnel and civilians in recent conflicts and terrorist attacks. Fragments that penetrate into the thoracic cavity are strongly associated with death due to the inherent vulnerability of the underlying structures. The aim of this study was to investigate the impact of fragment-simulating projectiles (FSPs) to tissues of the thorax in order to identify the thresholds of impact velocity for perforation through these tissues and the resultant residual velocity of the FSPs. A gas-gun system was used to launch 0.78-g cylindrical and 1.13-g spherical FSPs at intact porcine thoracic tissues from different impact locations. The sternum and rib bones were the most resistant to perforation, followed by the scapula and intercostal muscle. For both FSPs, residual velocity following perforation was linearly proportional to impact velocity. These findings can be used in the development of numerical tools for predicting the medical outcome of explosive events, which in turn can inform the design of public infrastructure, of personal protection, and of medical emergency response.

  • 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.

  • 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
    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
    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.

  • 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
    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

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