Publications

Journal article

Suzuki-Vidal F, Lebedev SV, Ciardi A, Pickworth LA, Rodriguez R, Gil JM, Espinosa G, Hartigan P, Swadling GF, Skidmore J, Hall GN, Bennett M, Bland SN, Burdiak G, de Grouchy P, Music J, Suttle L, Hansen E, Frank Aet al., 2015,

BOW SHOCK FRAGMENTATION DRIVEN BY A THERMAL INSTABILITY IN LABORATORY ASTROPHYSICS EXPERIMENTS

, Astrophysical Journal, Vol: 815, ISSN: 1538-4357

The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counterstreaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE pulsed-power generator. The jets have different flow velocities in the laboratory frame, and the experiments are driven over many times the characteristic cooling timescale. The initially smooth bow shock rapidly develops small-scale nonuniformities over temporal and spatial scales that are consistent with a thermal instability triggered by strong radiative cooling in the shock. The growth of these perturbations eventually results in a global fragmentation of the bow shock front. The formation of a thermal instability is supported by analysis of the plasma cooling function calculated for the experimental conditions with the radiative packages ABAKO/RAPCAL.

Journal article

Burdiak GC, Lebedev SV, Harvey-Thompson AJ, Hall GN, Swadling GF, Suzuki-Vidal F, Khoory E, Bland SN, Pickworth L, de Grouchy P, Skidmore J, Suttle L, Waisman EMet al., 2015,

Characterisation of the current switch mechanism in two-stage wire array Z-pinches

, Physics of Plasmas, Vol: 22, ISSN: 1089-7674

In this paper, we describe the operation of a two-stage wire array z-pinch driven by the 1.4 MA,240 ns rise-time Magpie pulsed-power device at Imperial College London. In this setup, an inversewire array acts as a fast current switch, delivering a current pre-pulse into a cylindrical load wirearray, before rapidly switching the majority of the generator current into the load after a100–150 ns dwell time. A detailed analysis of the evolution of the load array during the pre-pulse ispresented. Measurements of the load resistivity and energy deposition suggest significant bulk heatingof the array mass occurs. The 5 kA pre-pulse delivers 0.8 J of energy to the load, leaving itin a mixed, predominantly liquid-vapour state. The main current switch occurs as the inverse arraybegins to explode and plasma expands into the load region. Electrical and imaging diagnostics indicatethat the main current switch may evolve in part as a plasma flow switch, driven by the expansionof a magnetic cavity and plasma bubble along the length of the load array. Analysis ofimplosion trajectories suggests that approximately 1 MA switches into the load in 100 ns, correspondingto a doubling of the generator dI/dt. Potential scaling of the device to higher currentmachines is discussed. V

Journal article

Turrell A, Sherlock M, Rose SJ, 2015,

Ultra-fast collisional ion heating by electrostatic shocks

, Nature Communications, Vol: 6, ISSN: 2041-1723

High intensity lasers can be used to generate shockwaves which have found applications in nuclear fusion, proton imaging, cancer therapies, and materials science. Collisionless electrostatic shocks are one type of shockwave widely studied for applications involving ion acceleration. Here we show a novel mechanism for collisionlesselectrostatic shocks to heat small amounts of solid density matter to temperatures of ∼ keV in tens of femtoseconds. Unusually, electrons play no direct role in the heating, and it is the ions which determine the heating rate. Ions are heated due to an interplay between the electric field of the shock, the local density increaseduring the passage of the shock, and collisions between different species of ion. In simulations, these factors combine to produce rapid, localised heating of the lighter ion species. Although the heated volume is modest, this would be one of the fastest heating mechanisms discovered if demonstrated in the laboratory.

Journal article

Proud WG, Nguyen T-TN, Bo C, Butler BJ, Boddy RL, Williams A, Masouros S, Brown KAet al., 2015,

The High-Strain Rate Loading of Structural Biological Materials

, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, Vol: 46A, Pages: 4559-4566, ISSN: 1073-5623

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Citations: 4

Journal article

Proud WG, Williamson DM, Field JE, Walley SMet al., 2015,

Diagnostic techniques in deflagration and detonation studies

, Chemistry Central Journal, Vol: 9, ISSN: 1752-153X

Advances in experimental, high-speed techniques can be used to explore the processes occurring within energetic materials. This review describes techniques used to study a wide range of processes: hot-spot formation, ignition thresholds, deflagration, sensitivity and finally the detonation process. As this is a wide field the focus will be on small-scale experiments and quantitative studies. It is important that such studies are linked to predictive models, which inform the experimental design process. The stimuli range includes, thermal ignition, drop-weight, Hopkinson Bar and Plate Impact studies. Studies made with inert simulants are also included as these are important in differentiating between reactive response and purely mechanical behaviour.

Conference paper

Shahzad M, Tallents GJ, Culfa O, Rossall AK, Wilson LA, Rose SJ, Guilbaud O, Kazamias S, Pittman M, Cassou K, Demailly J, Delmas O, Mestrallain A, Farjardo M, Ros Det al., 2015,

Diagnosis of Radiation Heating in Iron Buried Layer Targets

, 14th International Conference on X-Ray Lasers, Publisher: Springer, Pages: 411-416, ISSN: 0930-8989

Extreme ultra-violet (EUV) laboratory lasers can be used to probe energy transport in laser irradiated solid targets. We report on a recent experiment undertaken at LASERIX whereby the heating of laser-irradiated targets containing a thin layer of iron (50 nm) encased in plastic (CH) was diagnosed using EUV laser (13.9 nm) back-lighter probing. The heating laser pulse duration was 35fs with focal irradiances of 3×10163×1016Wcm−2−2 and a deliberate prepulse 20 ps before the main pulse at irradiances of 3×10153×1015Wcm−2−2. A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission using IMP opacity values for the iron layer and the simulated transmissions compared to measured transmission values. When a deliberate prepulse is used to preform an expanding plastic plasma, it is found that radiation heating is dominant in the heating of the iron layer giving rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9nm laser radiation as the iron ionizes to Fe5+5+ and above.

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Journal article

Ampleford DJ, Bland SN, Jennings CA, Lebedev SV, Chittenden JP, McBride RD, Jones B, Serrano JD, Cuneo ME, Hall GN, Suzuki-Vidal F, Bott-Suzuki SCet al., 2015,

Investigating Radial Wire Array Z-Pinches as a Compact X-Ray Source on the Saturn Generator

, IEEE TRANSACTIONS ON PLASMA SCIENCE, Vol: 43, Pages: 3344-3352, ISSN: 0093-3813

Journal article

Macdonald J, Bland SN, Threadgold J, 2015,

A fibre based triature interferometer for measuring rapidly evolving, ablatively driven plasma densities

, Review of Scientific Instruments, Vol: 86, ISSN: 1089-7623

We report on the first use of a fibre interferometer incorporating triature analysis for measuring rapidly evolving plasma densities of ne ∼ 1013/cm3 and above, such as those produced by simple coaxial plasma guns. The resultant system is extremely portable, easy to field in experiments, relatively cheap to produce, and—with the exception of a small open area in which the plasma is sampled—safe in operation as all laser light is enclosed.

Journal article

Turrell AE, Sherlock M, Rose SJ, 2015,

Self-consistent inclusion of classical large-angle Coulomb collisions in plasma Monte Carlo simulations

, Journal of Computational Physics, Vol: 299, Pages: 144-155, ISSN: 1090-2716

Large-angle Coulomb collisions allow for the exchange of a significant proportion of the energy of a particle in a single collision, but are not included in models of plasmas based on fluids, the Vlasov-Fokker-Planck equation, or currently available plasma Monte Carlo techniques. Their unique effects include the creation of fast ‘knock-on’ ions, which may be more likely to undergo certain reactions, and distortions to ion distribution functions relative to what is predicted by small-angle collision only theories. We present a computational method which uses Monte Carlo techniques to include the effects of large-angle Coulomb collisions in plasmas and which self-consistently evolves distribution functions according to the creation of knock-on ions of any generation. The method is used to demonstrate ion distribution function distortions in an inertial confinement fusion (ICF) relevant scenario of the slowing of fusion products.

Journal article

Swadling GF, Lebedev SV, Harvey-Thompson AJ, Rozmus W, Burdiak G, Suttle L, Patankar S, Smith RA, Bennett M, Hall GN, Suzuki-Vidal F, Bland S, Yuan Jet al., 2015,

Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

, PHYSICS OF PLASMAS, Vol: 22, ISSN: 1070-664X

Journal article

Jones DR, Chapman DJ, Eakins DE, 2015,

A Method for Studying the Temperature Dependence of Dynamic Fracture and Fragmentation

, Journal of Visualized Experiments, Vol: 100, ISSN: 1940-087X

The dynamic fracture of a body is a late-stage phenomenon typically studied under simplified conditions, in which a sample is deformed underuniform stress and strain rate. This can be produced by evenly loading the inner surface of a cylinder. Due to the axial symmetry, as the cylinderexpands the wall is placed into a tensile hoop stress that is uniform around the circumference. While there are various techniques to generatethis expansion such as explosives, electromagnetic drive, and existing gas gun techniques they are all limited in the fact that the sample cylindermust be at room temperature. We present a new method using a gas gun that facilitates experiments on cylinders from 150 K to 800 K with aconsistent, repeatable loading. These highly diagnosed experiments are used to examine the effect of temperature on the fracture mechanismsresponsible for failure, and their resulting influence on fragmentation statistics. The experimental geometry employs a steel ogive located insidethe target cylinder, with the tip located about halfway in. A single stage light gas gun is then used to launch a polycarbonate projectile into thecylinder at 1,000 m/sec-1. The projectile impacts and flows around the rigid ogive, driving the sample cylinder from the inside. The use of a nondeformingogive insert allows us to install temperature control hardware inside the rear of the cylinder. Liquid nitrogen (LN2) is used for coolingand a resistive high current load for heating. Multiple channels of upshifted photon Doppler velocimetry (PDV) track the expansion velocityalong the cylinder enabling direct comparison to computer simulations, while High speed imaging is used to measure the strain to failure. Therecovered cylinder fragments are also subject to optical and electron microscopy to ascertain the failure mechanism.

Journal article

Butler BJ, Bo C, Boddy RL, Arora H, Williams A, Proud WG, Brown KAet al., 2015,

Composite nature of fresh skin revealed during compression

, Bioinspired, Biomimetic and Nanobiomaterials, Vol: 4, Pages: 133-139, ISSN: 2045-9858

Journal article

Walley SM, Field JE, Biers RA, Proud WG, Williamson DM, Jardine APet al., 2015,

The Use of Glass Anvils in Drop-Weight Studies of Energetic Materials

, PROPELLANTS EXPLOSIVES PYROTECHNICS, Vol: 40, Pages: 351-365, ISSN: 0721-3115

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Citations: 26

Journal article

Burdiak GC, Lebedev SV, Suzuki-Vidal F, Swadling GF, Bland SN, Niasse N, Suttle L, Bennet M, Hare J, Weinwurm M, Rodriguez R, Gil J, Espinosa Get al., 2015,

Cylindrical liner Z-pinch experiments for fusion research and high-energy-density physics

, Journal of Plasma Physics, Vol: 81, ISSN: 1469-7807

A gas-filled cylindrical liner z-pinch configuration has been used to drive convergentradiative shock waves into different gases at velocities of 20–50 km s−1. On applicationof the 1.4 MA, 240 ns rise-time current pulse produced by the Magpie generatorat Imperial College London, a series of cylindrically convergent shock waves aresequentially launched into the gas-fill from the inner wall of the liner. This occurswithout any bulk motion of the liner wall itself. The timing and trajectories of theshocks are used as a diagnostic tool for understanding the response of the linerz-pinch wall to a large pulsed current. This analysis provides useful data on theliner resistivity, and a means to test equation of state (EOS) and material strengthmodels within MHD simulation codes. In addition to providing information on linerresponse, the convergent shocks are interesting to study in their own right. The shocksare strong enough for radiation transport to influence the shock wave structure. Inparticular, we see evidence for both radiative preheating of material ahead of theshockwaves and radiative cooling instabilities in the shocked gas. Some preliminaryresults from initial gas-filled liner experiments with an applied axial magnetic fieldare also discussed.

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Journal article

Zucchini F, Bland SN, Chauvin C, Combes P, Sol D, Loyen A, Roques B, Grunenwald Jet al., 2015,

Characteristics of a molybdenum X-pinch X-ray source as a probe source for X-ray diffraction studies

, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 86, ISSN: 0034-6748

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Citations: 10

Journal article

Winter RE, Cotton M, Harris EJ, Chapman DJ, Eakins Det al., 2015,

Generation of ramp waves using variable areal density flyers

, Shock Waves, Vol: 26, Pages: 395-401, ISSN: 0938-1287

Ramp loading using graded density impactors as flyers in gas-gun-driven plate impact experiments can yield new and useful information about the equation of state and the strength properties of the loaded material. Selective Laser Melting, an additive manufacturing technique, was used to manufacture a graded density flyer, termed the “bed-of-nails” (BON). A 2.5-mm-thick ×× 99.4-mm-diameter solid disc of stainless steel formed a base for an array of tapered spikes of length 5.5 mm and spaced 1 mm apart. The two experiments to test the concept were performed at impact velocities of 900 and 1100 m/s using the 100-mm gas gun at the Institute of Shock Physics at Imperial College London. In each experiment, a BON flyer was impacted onto a copper buffer plate which helped to smooth out perturbations in the wave profile. The ramp delivered to the copper buffer was in turn transmitted to three tantalum targets of thicknesses 3, 5 and 7 mm, which were mounted in contact with the back face of the copper. Heterodyne velocimetry (Het-V) was used to measure the velocity–time history, at the back faces of the tantalum discs. The wave profiles display a smooth increase in velocity over a period of ∼2.5μs∼2.5μs , with no indication of a shock jump. The measured profiles have been analysed to generate a stress vs. volume curve for tantalum. The results have been compared with the predictions of the Sandia National Laboratories hydrocode, CTH.

Conference paper

Hare JD, Lebedev SV, Bennett M, Bland SN, Burdiak GC, Suttle L, Suzuki-Vidal F, Swadling GFet al., 2015,

Photo-ionisation of gas by x-rays from a wire array z-pinch

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Conference paper

Burdiak GC, Lebedev SV, Bland S, Suzuki-Vidal F, Swadling GF, Suttle L, Bennet M, Williams RJR, Blesener Ket al., 2015,

Radiative precursors driven by converging blast waves in noble gases

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Conference paper

Cotton M, Chapman D, Winter R, Harris E, Eakins Det al., 2015,

Tailored ramp wave generation in gas gun experiments

, 11th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading (DYMAT), Publisher: E D P SCIENCES, ISSN: 2100-014X

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Citations: 1

Journal article

Eakins D, Chapman D, 2014,

X-ray imaging of subsurface dynamics in high-Z materials at the Diamond Light Source

, Review of Scientific Instruments, Vol: 85, Pages: 123708-123708, ISSN: 1089-7623

In this paper, we describe a new approach enabling study of subsurface dynamics in high-Z materials using the unique combination of high-energy synchrotron X-rays, a hybrid bunch structure, and a new dynamic loading platform. We detail the design and operation of the purpose-built, portable small bore gas-gun, which was installed on the I12 high-energy beamline at the Diamond Light Source and used to drive compression waves into solid and porous metal targets. Using a hybrid bunch structure and broadband X-ray pulses of up to 300 keV, radiographic snapshots were captured during various dynamic deformation processes in cm-scale specimens, thereby contributing to a more complete understanding of the evolution of mesoscale damage. Importantly, we highlight strategies for overcoming the challenges associated with using high-energy X-rays, and suggest areas for improvement needed to advance dynamic imaging through large-scale samples of relevance to engineering scenarios. These preliminary measurements demonstrate the feasibility of probing highly transient phenomena using the presented methodology.

Journal article

Sherlock, Hill EG, Evans, Rose, W Rozmuset al., 2014,

In-depth Plasma-Wave Heating of Dense Plasma Irradiated by Short Laser Pulses

, Physical Review Letters, Vol: 113, ISSN: 1079-7114

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Journal article

Swadling GF, Lebedev SV, Hall GN, Patankar S, Stewart NH, Smith RA, Harvey-Thompson AJ, Burdiak GC, de Grouchy P, Skidmore J, Suttle L, Suzuki-Vidal F, Bland SN, Kwek KH, Pickworth L, Bennett M, Hare JD, Rozmus W, Yuan Jet al., 2014,

Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry

, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 85, ISSN: 0034-6748

Journal article

Kanel GI, Garkushin GV, Savinykh AS, Razorenov SV, de Resseguier T, Proud WG, Tyutin MRet al., 2014,

Shock response of magnesium single crystals at normal and elevated temperatures

, Journal of Applied Physics, Vol: 116, Pages: 1-9, ISSN: 0021-8979

A series of magnesium single crystals, from 0.2 to 3 mm thick, were shock loaded in directions parallel and perpendicular to the c-axis of the hexagonal closed packed (hcp) structure and at 45° to the c-axis. Shock compression along the c-axis is associated with the largest Hugoniot elastic limit (HEL) for this material. Microscopic observation of recovered c-cut samples demonstrated intense twinning with a greater density of twins near the impact surface. The low-energy basal slip was activated by shock loading along the inclined direction and has the smallest HEL. In all cases, we observe the decay of the elastic precursor wave and growth of the HEL with increasing temperature. For the inclined shock compression after the HEL, two plastic waves were found where the stress level of the first plastic wave depends on the peak shock stress. Finally, the largest spall strength was along the transversal direction and the smallest in the off-axis direction. The fracture surface of the sample of transversal orientation contains numerous groves oriented along the base planes of the crystals.

Journal article

Tunnell R, Ashcroft M, Dale R, Tod D, Proud WGet al., 2014,

Ammonium Perchlorate, Friend or Foe?

, PROPELLANTS EXPLOSIVES PYROTECHNICS, Vol: 39, Pages: 707-713, ISSN: 0721-3115

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Citations: 2

Journal article

Turrell AE, Sherlock M, Rose SJ, 2014,

Effects of Large-Angle Coulomb Collisions on Inertial Confinement Fusion Plasmas (vol 112, 245002, 2014)

, PHYSICAL REVIEW LETTERS, Vol: 113, ISSN: 0031-9007

Journal article

Tunnell R, Ashcroft M, Dale R, Tod D, Proud WGet al., 2014,

Ammonium Perchlorate, Friend or Foe? Part 1: The Influence of this Oxidizer on the Aging Behavior of Propellant Compositions

, PROPELLANTS EXPLOSIVES PYROTECHNICS, Vol: 39, Pages: 504-510, ISSN: 0721-3115

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Citations: 3

Journal article

Hill EG, Rose SJ, 2014,

Non-thermal enhancement of electron-positron pair creation in burning thermonuclear laboratory plasmas

, High Energy Density Physics

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Journal article

Hall GN, Burdiak GC, Suttle L, Stuart NH, Swadling GF, Lebedev SV, Smith RA, Patankar S, Suzuki Vidal F, de Grouchy P, Harvey-Thompson AJ, Bennett M, Bland SN, Pickworth L, Skidmore Jet al., 2014,

Monochromatic radiography of high energy density physics experiments on the MAGPIE generator

, Review of Scientific Instruments, Vol: 85, ISSN: 1089-7623

A monochromatic X-ray backlighter based on Bragg reflection from a spherically bent quartzcrystal has been developed for the MAGPIE pulsed power generator at Imperial College (1.4 MA,240 ns) [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (2005)]. This instrument has been usedto diagnose high energy density physics experiments with 1.865 keV radiation (Silicon He-α) froma laser plasma source driven by a ∼7 J, 1 ns pulse from the Cerberus laser. The design of thediagnostic, its characterisation and performance, and initial results in which the instrument was usedto radiograph a shock physics experiment on MAGPIE are discussed.

Journal article

Turrell AE, Rose SJ, Sherlock M, 2014,

Effects of Large-Angle Coulomb Collisions on Inertial Confinement Fusion Plasmas

, Physical Review Letters, Vol: 112

Large-angle Coulomb collisions affect the rates of energy and momentum exchange in a plasma, and it is expected that their effects will be important in many plasmas of current research interest, including in inertial confinement fusion. Their inclusion is a long-standing problem, and the first fully self-consistent method for calculating their effects is presented. This method is applied to “burn” in the hot fuel in inertial confinement fusion capsules and finds that the yield increases due to an increase in the rate of temperature equilibration between electrons and ions which is not predicted by small-angle collision theories. The equilibration rate increases are 50%–100% for number densities of 10^{30} m^{−3} and temperatures around1 keV.

Journal article

Pike OJ, Mackenroth F, Hill EG, Rose SJet al., 2014,

A photon-photon collider in a vacuum hohlraum

, Nature Photonics, Vol: 8, Pages: 434-436, ISSN: 1749-4885

The ability to create matter from light is amongst the most striking predictions of quantum electrodynamics. Experimental signatures of this have been reported in the scattering of ultra-relativistic electron beams with laser beams1,2, intense laser–plasma interactions3 and laser-driven solid target scattering4. However, all such routes involve massive particles. The simplest mechanism by which pure light can be transformed into matter, Breit–Wheeler pair production (γγ′ → e+e−)5, has never been observed in the laboratory. Here, we present the design of a new class of photon–photon collider in which a gamma-ray beam is fired into the high-temperature radiation field of a laser-heated hohlraum. Matching experimental parameters to current-generation facilities, Monte Carlo simulations suggest that this scheme is capable of producing of the order of 105 Breit–Wheeler pairs in a single shot. This would provide the first realization of a pure photon–photon collider, representing the advent of a new type of high-energy physics experiment.

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