Publications

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

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

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

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Citations: 6

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

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

Cumming AS, Proud WG, 2020,

<i>In Memoriam</i> Professor John E. Field, FRS, OBE 1936 to 2020

, PROPELLANTS EXPLOSIVES PYROTECHNICS, Vol: 45, Pages: 1829-1829, ISSN: 0721-3115

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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Citations: 7

Conference paper

Proud WG, O'Brien S, Wilson MA, 2020,

Elicitation of knowledge from a defence expert

, ISSN: 1742-6588

The aim of this work is to understand the way that a defence expert defines the concept of importance in relation to the ideas contained in a scientific document. The expert's views on the importance of the concepts in this document were elicited in two phases. In the first phase, the expert was asked to summarise an eight-page document on the effects of electromagnetic fields on propellant combustion. Completion of this task generated a series of 'key points'. Phase two of the methodology was a sit-down interview with the expert. This interview comprised three parts: asking the expert to talk through why each of the key points were important, asking the expert to sort the key points into categories according to how important they are and then asking the expert to generate categories of why the points are important. The techniques used for expert elicitation proved highly successful in relation to this domain of knowledge. Not only were the procedures able to extract the underlying categories through which the expert structured their understanding of the field, but the results indicated reliability in the content of knowledge extracted through different methods. Subsequent papers in this project compare this work to parallel analysis conducted using Natural Language Processing tools.

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Journal article

Felten M, Fries M, Pullen A, Proud WG, Jung Aet al., 2020,

Investigation of Strain-Rate Effects in Ni/PU Hybrid Foams under Low-Impact Velocities

, ADVANCED ENGINEERING MATERIALS, Vol: 22, ISSN: 1438-1656

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Citations: 3

Journal article

Nguyen TT, Meek G, Breeze J, Masouros Set al., 2020,

Gelatine backing affects the performance of single-layer ballistic-resistant materials against blast fragments

, Frontiers in Bioengineering and Biotechnology, Vol: 8, Pages: 1-10, ISSN: 2296-4185

Penetrating trauma by energized fragments is the most common injury from explosive devices, the main threat in the contemporary battlefield. Such devices produce projectiles dependent upon their design, including preformed fragments, casings, glass, or stones; these are subsequently energized to high velocities and cause serious injuries to the body. Current body armor focuses on the essential coverage, which is mainly the thoracic and abdominal area, and can be heavy and cumbersome. In addition, there may be coverage gaps that can benefit from the additional protection provided by one or more layers of lightweight ballistic fabrics. This study assessed the performance of single layers of commercially available ballistic protective fabrics such as Kevlar®, Twaron®, and Dyneema®, in both woven and knitted configurations. Experiments were carried out using a custom-built gas-gun system, with a 0.78-g cylindrical steel fragment simulating projectile (FSP) as the impactor, and ballistic gelatine as the backing material. FSP velocity at 50% risk of material perforation, gelatine penetration, and high-risk wounding to soft tissue, as well as the depth of penetration (DoP) against impact velocity and the normalized energy absorption were used as metrics to rank the performance of the materials tested. Additional tests were performed to investigate the effect of not including a soft-tissue simulant backing material on the performance of the fabrics. The results show that a thin layer of ballistic material may offer meaningful protection against the penetration of this FSP. Additionally, it is essential to ensure a biofidelic boundary condition as the protective efficacy of fabrics was markedly altered by a gelatine backing.

Journal article

Miller SM, Slutz SA, Bland SN, Klein SR, Campbell PC, Woolstrum JM, Kuranz CC, Gomez MR, Jordan NM, McBride RDet al., 2020,

A pulsed-power implementation of “Laser Gate” for increasing laser energy coupling and fusion yield in magnetized liner inertial fusion (MagLIF)

, Review of Scientific Instruments, Vol: 91, Pages: 1-9, ISSN: 0034-6748

Magnetized Liner Inertial Fusion (MagLIF) at Sandia National Laboratories involves a laser preheating stage where a few-ns laser pulse passes through a few-micron-thick plastic window to preheat gaseous fusion fuel contained within the MagLIF target. Interactions with this window reduce heating efficiency and mix window and target materials into the fuel. A recently proposed idea called “Laser Gate” involves removing the window well before the preheating laser is applied. In this article, we present experimental proof-of-principle results for a pulsed-power implementation of Laser Gate, where a thin current-carrying wire weakens the perimeter of the window, allowing the fuel pressure to push the window open and away from the preheating laser path. For this effort, transparent targets were fabricated and a test facility capable of studying this version of Laser Gate was developed. A 12-frame bright-field laser schlieren/shadowgraphy imaging system captured the window opening dynamics on microsecond timescales. The images reveal that the window remains largely intact as it opens and detaches from the target. A column of escaping pressurized gas appears to prevent the detached window from inadvertently moving into the preheating laser path.

Journal article

Escauriza EM, Duarte JP, Chapman DJ, Rutherford ME, Farbaniec L, Jonsson JC, Smith LC, Olbinado MP, Skidmore J, Foster P, Ringrose T, Rack A, Eakins DEet al., 2020,

Collapse dynamics of spherical cavities in a solid under shock loading

, SCIENTIFIC REPORTS, Vol: 10, ISSN: 2045-2322

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Citations: 12

Journal article

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

The risk of fracture to the tibia from a fragment simulating projectile

, Journal of The Mechanical Behavior of Biomedical Materials, Vol: 102, ISSN: 1751-6161

Penetrating injuries due to fragments energised by an explosive event are life threatening and are associated with poor clinical and functional outcomes. The tibia is the long bone most affected in survivors of explosive events, yet the risk of penetrating injury to it has not been quantified. In this study, an injury-risk assessment of penetrating injury to the tibia was conducted using a gas-gun system with a 0.78-g cylindrical fragment simulating projectile. An ovine tibia model was used to generate the injury-risk curves and human cadaveric tests were conducted to validate and scale the results of the ovine model. The impact velocity at 50% risk (±95% confidence intervals) for EF1+, EF2+, EF3+, and EF4+ fractures to the human tibia – using the modified Winquist-Hansen classification – was 271 ± 30, 363 ± 46, 459 ± 102, and 936 ± 182 m/s, respectively. The scaling factor for the impact velocity from cadaveric ovine to human was 2.5. These findings define the protection thresholds to improve the injury outcomes for fragment penetrating injury to the tibia.

Conference paper

Tear GR, Proud WG, 2020,