Results
- Showing results for:
- Reset all filters
Search results
-
Journal articleBland SN, Krasik YAE, Yanuka D, et al., 2017,
Generation of highly symmetric, cylindrically convergent shockwaves in water
, Physics of Plasmas, Vol: 24, ISSN: 1089-7674We report on pulsed power driven, exploding copper wire array experiments conducted to generate cylindrical convergent shockwaves in water employing μs risetime currents >550 kA in amplitude and with stored energies of >15 kJ—a substantial increase over previous results. The experiments were carried out on the recently constructed Mega-Ampere-Compression-and-Hydrodynamics facility at Imperial College London in collaboration with colleagues of Technion, Israel. 10 mm diameter arrays consisting of 60 × 130 μm wires were utilized, and the current and voltage diagnostics of the load region suggested that ∼8 kJ of energy was deposited in the wires (and the load region close to the wires) during the experiments, resulting in the formation of dense, highly resistive plasmas that rapidly expanded driving the shockwaves in water. Laser-backlit framing images of the shockfront were obtained at radii <0.25 mm for the first time, and there was strong evidence that even at radii <0.1 mm this front remains stable, resulting in a convergence ratio of >50:1. Framing images and streak photographs showed that the velocity of the shockwave reached ∼7.5 km s−1 at 0.1 mm from the axis. 2D hydrodynamic simulations that match the experimentally obtained implosion trajectory suggest that pressures >1 Mbar are produced within 10 μm of the axis along with water densities of 3gcm−3 and temperatures of many 1000 s of Kelvin. Under these conditions, Quotidian Equation of State suggests that a strongly coupled plasma with an ionization fraction of ∼0.7 would be formed. The results represent a “stepping stone” in the application of the technique to drive different material samples into high pressure, warm dense matter regimes with compact, university scale generators, and provide support in scaling the technique to multi-mega ampere
-
Journal articleBurdiak GC, Lebedev SV, Bland SN, et al., 2017,
The structure of bow shocks formed by the interaction of pulsed-power driven magnetised plasma flows with conducting obstacles
, PHYSICS OF PLASMAS, Vol: 24, ISSN: 1070-664XWe present an experimental study of the development and structure of bow shocks produced by the interaction of a magnetised, collisional, super-Alfvénic plasma flow with conducting cylindrical obstacles. The plasma flow with an embedded, frozen-in magnetic field (ReM ∼ 20) is produced by the current-driven ablation of fine aluminium wires in an inverse, exploding wire array z-pinch. We show that the orientation of the embedded field with respect to the obstacles has a dramatic effect on the bow shock structure. When the field is aligned with the obstacle, a sharp bow shock is formed with a global structure that is determined simply by the fast magneto-sonic Mach number. When the field is orthogonal to the obstacle, magnetic draping occurs. This leads to the growth of a magnetic precursor and the subsequent development of a magnetised bow shock that is mediated by two-fluid effects, with an opening angle and a stand-off distance, that are both many times larger than in the parallel geometry. By changing the field orientation, we change the fluid regime and physical mechanisms that are responsible for the development of the bow shocks. MHD simulations show good agreement with the structure of well-developed bow shocks. However, collisionless, two-fluid effects will need to be included within models to accurately reproduce the development of the shock with an orthogonal B-field.
-
Journal articleRutherford ME, Chapman DJ, Derrick JG, et al., 2017,
Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale
, Scientific Reports, Vol: 7, ISSN: 2045-2322Chondritic meteorites are fragments of asteroids, the building blocks of planets, that retain a record of primordialprocesses. Important in their early evolution was impact-driven lithification, where a porous mixture of millimetre-scale chondrule inclusions and sub-micrometre dust was compacted into rock. In this Article, the shock compression ofanalogue precursor chondrite material was probed using state of the art dynamic X-ray radiography. Spatially-resolvedshock and particle velocities, and shock front thicknesses were extracted directly from the radiographs, representinga greatly enhanced scope of data than could be measured in surface-based studies. A statistical interpretation of themeasured velocities showed that mean values were in good agreement with those predicted using continuum-levelmodelling and mixture theory. However, the distribution and evolution of wave velocities and wavefront thicknesseswere observed to be intimately linked to the mesoscopic structure of the sample. This Article provides the first detailedexperimental insight into the distribution of extreme states within a shocked powder mixture, and represents the firstmesoscopic validation of leading theories concerning the variation in extreme pressure-temperature states during theformation of primordial planetary bodies.
-
Journal articleHoarty DJ, Sircombe N, Beiersdorfer P, et al., 2017,
Modelling K shell spectra from short pulse heated buried microdot targets
, High Energy Density Physics, Vol: 23, Pages: 178-183, ISSN: 1574-1818K shell X-ray emission measurements have been used to diagnose plasma conditions in short-pulse heated buried microdot targets on the Orion high power laser. These experiments have been used to validate simulations of short pulse laser-solid interaction that combine hybrid PIC modelling of the laser absorption with radiation-hydrodynamics simulations including an electron transport model. Comparison of these simulations with streaked K shell spectroscopy show the importance of including radial gradients in fitting the spectra. An example is presented of the emission of sulphur from a 50 µm diameter microdot sample buried in a plastic foil. Previously agreement between simulation and experiment was obtained only by treating the absorbed energy, electron temperature and beam divergence as fitting parameters. The good agreement obtained in this work used the measured laser energy and laser pulse length and calculated the laser-solid target interaction from first principles.
-
Journal articleOta TA, Chapman DJ, Eakins DE, 2017,
Monte-Carlo modelling to determine optimum filter choices for sub-microsecond optical pyrometry
, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 88, ISSN: 0034-6748 -
Journal articleHoarty DJ, Hill EG, Beiersdorfer P, et al., 2017,
Measurements of plasma spectra from hot dense elements and mixtures at conditions relevant to the solar radiative zone
, AIP Conference Proceedings, Vol: 1811, ISSN: 1551-7616X-ray emission spectroscopy has been used to study hot dense plasmas produced using high power laser irradiation of dot samples buried in low Z foils of plastic or diamond. By combining a high contrast short pulse (picosecond timescale) laser beam operating in second harmonic with long pulse (nanosecond timescale) laser beams in third harmonic, and with pulse shaping of the long pulse beams, a range of plasma temperatures from 400eV up to 2.5keV and electron densities from 5e22 up to 1e24/cc have been accessed. Examples are given of measurements of dense plasma effects such as ionization potential depression and line-broadening from the K-shell emission spectra of a range of low Z elements and mixtures and compared to model prediction. Detailed spectra from measurements of the L-shell emission from mid-Z elements are also presented for an example spectrum of germanium. These data are at conditions found in stellar interiors and in particular in the radiative zone of the sun. The plasma conditions are inferred from comparison of the measured spectra to detailed modeling using atomic kinetics and spectral synthesis codes.
-
Journal articleWhite TG, Patten JRW, Wan K-H, et al., 2017,
A single camera three-dimensional digital image correlation system for the study of adiabatic shear bands
, STRAIN, Vol: 53, ISSN: 1475-1305 -
Conference paperStafford SJP, Chapman DJ, Bland SN, et al., 2017,
Observations on the Nucleation of Ice VII in Compressed Water
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperAmott R, Harris EJ, Winter RE, et al., 2017,
The Fracture and Fragmentation Behaviour of Additively Manufactured Stainless Steel 316L
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperEscobedo JP, Chapman DJ, Laws KJ, et al., 2017,
EEffects of Chemical Composition on the Shock Response of Zr-based Metallic Glasses
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperTear GR, Chapman DJ, Eakins D, et al., 2017,
Birefringence measurements in single crystal sapphire and calcite shocked along the a axis
, Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter, Publisher: AIP Publishing, ISSN: 1551-7616Calcite and sapphire were shock compressed along the ⟨101⎯⎯0⟩ direction (a axis) in a plate impact configuration. Polarimetery and Photonic Doppler Velocimetery (PDV) were used to measure the change in birefringence with particle velocity in the shock direction. Results for sapphire agree well with linear photoelastic theory and current literature showing a linear relationship between birefringence and particle velocity up to 310 m s−1. A maximum change in birefringence of 5% was observed. Calcite however showed anomolous behaviour with no detectable change in birefringence (less than 0.1%) over the range of particle velocities studied (up to 75 m s−1).
-
Conference paperBell DJ, Chapman DJ, 2017,
Phase Doppler Anemometry as an Ejecta Diagnostic
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperJones DR, Chapman DJ, Eakins DE, 2017,
Gas Gun Driven Dynamic Fracture and Fragmentation of Ti-6Al-4V Cylinders at Initial Temperatures Between 150 K and 750 K
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperNguyen T-TN, Proud WG, 2017,
An Investigation of A Reticulated Foam - Perforated Steel Sheet Combination As A Blast Mitigation Structure
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperKhan AS, Proud WG, 2017,
Temperature and Strain Rate Effects on the Piezoelectric Charge Production of PZT 95/5
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperKhan AS, Wilgeroth J, Balzer J, et al., 2017,
Comparison of Epoxy-Based Encapsulating Materials over Temperature and Strain Rate
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperIrwin R, White S, Warwick JR, et al., 2017,
Study of Ar photoionisation physics using VULCAN
The values achieved for the photoionisation parameter (ξ) are, to our knowledge, the highest to be achieved in the laboratory. This will benefit future understanding of the physics of numerous astrophysical bodies such as Seyfert galaxies. A possible future experiment would be to try to achieve a higher value for ξ at a larger laser facility such as GEKKO, NIF or OMEGA, and to extend the study to other gases such as Neon.
-
Conference paperButler BJ, Sory DR, Nguyen T-TN, et al., 2017,
Characterization of Focal Muscle Compression Under Impact Loading
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperBadham H, Chalmers M, Thuy-Tien NN, et al., 2017,
The Propagation of Blast Pulses through Dampened Granular Media
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AIP Publishing, ISSN: 1551-7616The propagation of stress through granular and dampened granular material has been reported previously, the addition of significant amounts of liquid in granular beds causes the mechanism of transmission of blast from one of percolation through the bed pores to one of stress transmission through the granules of the bed. It has been shown, however, that limited amounts liquid can retard propagation within blast-loaded beds by approximately an order of magnitude. This paper presents data on percolation through dampened granular beds using a shock tube as the pressure driver. The effect of particle shape and size was investigated using angular grains of quartz sand as well as smooth glass microspheres. The effect of addition of small amounts of liquids is presented.
-
Conference paperProud WG, Chapman DJ, Eakins DE, 2017,
The stress and ballistic properties of granular materials
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AIP Publishing, ISSN: 1551-7616Granular materials are widespread in nature and in manufacturing. Their particulate nature gives a compressive strength of a similar order of magnitude as many continuous solids, a vanishingly small tensile strength and variable shear strength, highly dependent on the loading conditions. Previous studies have shown the effect of composition, morphology and particle size, however, compared to metals and polymers, granular materials are not so well understood. This paper will present some recent results for granular materials, placing these within the wider context. Two areas will be dealt with (i) the effect of the skeletal strength of the material and (ii) the displacements associated with ballistic impact. One clear observation is the similarity of behavior of quartz-sands in compression across a range of particle size. However, the precise pathway of compression is strongly dependent on the initial conditions e.g. density and connectivity within the granular bed, as emphasized by some data for quasi-static compression of sand. To fully embrace the range of behaviours seen requires the development of a suitable parameter to describe the material, the paper concludes with a discussion of one of those approaches.
-
Conference paperSory DR, Areias AC, Overby DR, et al., 2017,
Novel method to dynamically load cells in 3D-hydrogels culture for blast injury studies
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Conference paperTear GR, Proud WG, 2017,
Predicting the Optical Behaviour of Shock Compressed Dielectrics
, 19th Biennial American-Physical-Society (APS) Conference on Shock Compression of Condensed Matter (SCCM), Publisher: AMER INST PHYSICS, ISSN: 0094-243X -
Book chapterRose S, 2017,
Particle Interactions in High-Temperature Plasmas Supervisor's Foreword
, PARTICLE INTERACTIONS IN HIGH-TEMPERATURE PLASMAS, Publisher: SPRINGER-VERLAG BERLIN, Pages: V-V, ISBN: 978-3-319-63446-3 -
Journal articleWinter RE, Stirk SM, Harris EJ, et al., 2016,
A technique for studying the response of materials to high rate, high strain deformation
, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, Vol: 97, Pages: 116-126, ISSN: 0734-743X -
Journal articleTorchio R, Occelli F, Mathon O, et al., 2016,
Probing local and electronic structure in Warm Dense Matter: single pulse synchrotron x-ray absorption spectroscopy on shocked Fe
, Scientific Reports, Vol: 6, ISSN: 2045-2322Understanding Warm Dense Matter (WDM), the state of planetary interiors, is a new frontier in scienti c research. There exists very little experimental data probing WDM states at the atomic level to test current models and those performed up to now are limited in quality. Here, we report a proof-of- principle experiment that makes microscopic investigations of materials under dynamic compression easily accessible to users and with data quality close to that achievable at ambient. Using a single100 ps synchrotron x-ray pulse, we have measured, by K-edge absorption spectroscopy, ns-lived equilibrium states of WDM Fe. Structural and electronic changes in Fe are clearly observed for the rst time at such extreme conditions. The amplitude of the EXAFS oscillations persists up to 500 GPa and 17000 K, suggesting an enduring local order. Moreover, a discrepancy exists with respect to theoretical calculations in the value of the energy shift of the absorption onset and so this comparison should help to re ne the approximations used in models.
-
Thesis dissertationNguyen TT, 2016,
The Characterisation of A Shock Tube System for Blast Injury Studies
-
Journal articlePike OJ, Rose SJ, 2016,
Transport coefficients of a relativistic plasma
, Physical Review E, Vol: 93, ISSN: 1539-3755In this work, a self-consistent transport theory for a relativistic plasma is developed.Using the notation of Braginskii [S. I. Braginskii, in Reviews of Plasma Physics, ed. M. A.Leontovich (1965), Vol. 1, p.174], we provide semi-analytical forms of the electrical resistivity,thermoelectric and thermal conductivity tensors for a Lorentzian plasma in a magnetic field.This treatment is then generalized to plasmas with arbitrary atomic number by numericallysolving the linearized Boltzmann equation. The corresponding transport coefficients arefitted by rational functions in order to make them suitable for use in radiation-hydrodynamicsimulations and transport calculations. Within the confines of linear transport theory andon the assumption that the plasma is optically thin, our results are valid for temperatures upto a few MeV. By contrast, classical transport theory begins to incur significant errors abovekBT ∼ 10 keV, e.g., the parallel thermal conductivity is suppressed by 15% at kBT = 20keV due to relativistic effects
-
Journal articleSwadling GF, Lebedev SV, Hall GN, et al., 2016,
Experimental investigations of ablation stream interaction dynamics in tungsten wire arrays: interpenetration, magnetic field advection, and ion deflection
, Physics of Plasmas, Vol: 23, ISSN: 1089-7674Experiments have been carried out to investigate the collisional dynamics of ablation streams produced by cylindrical wire array z-pinches. A combination of laser interferometric imaging, Thomson scattering, and Faraday rotationimaging has been used to make a range of measurements of the temporal evolution of various plasma and flow parameters. This paper presents a summary of previously published data, drawing together a range of different measurements in order to give an overview of the key results. The paper focuses mainly on the results of experiments with tungsten wire arrays. Early interferometric imagingmeasurements are reviewed, then more recent Thomson scattering measurements are discussed; these measurements provided the first direct evidence of ablation stream interpenetration in a wire array experiment. Combining the data from these experiments gives a view of the temporal evolution of the tungsten stream collisional dynamics. In the final part of the paper, we present new experimental measurements made using an imagingFaraday rotationdiagnostic. These experiments investigated the structure of magnetic fields near the array axis directly; the presence of a magnetic field has previously been inferred based on Thomson scattering measurements of ion deflection near the array axis. Although the Thomson and Faradaymeasurements are not in full quantitative agreement, the Faraday data do qualitatively supports the conjecture that the observed deflections are induced by a static toroidal magnetic field, which has been advected to the array axis by the ablation streams. It is likely that detailed modeling will be needed in order to fully understand the dynamics observed in the experiment.
-
Journal articleHaerendel G, Suttle L, Lebedev SV, et al., 2016,
Stop layer: a flow braking mechanism in space and support from a lab experiment
, Plasma Physics and Controlled Fusion, Vol: 58, ISSN: 1361-6587The paper presents short summaries and a synopsis of two completely independent discoveries of a fast flow braking process, one realized by a laboratory experiment (Lebedev et al 2014 Phys. Plasmas 21 056305), the other by theoretical reasoning stimulated by auroral observation (Haerendel 2015a J. Geophys. Res. Space Phys. 120 1697–714). The first has been described as a magnetically mediated sub-shock forming when a supersonic plasma flow meets a wall. The second tried to describe what happens when a high-beta plasma flow from the central magnetic tail meets the strong near-dipolar field of the magnetosphere. The term stop layer signals that flow momentum and energy are directly coupled to a magnetic perturbation field generated by a Hall current within a layer of the width of c/ω pi and immediately propagated out of the layer by kinetic Alfvén waves. As the laboratory situation is not completely collision-free, energy transfer from ions to electrons and subsequent radiative losses are likely to contribute. A synopsis of the two situations identifies and discusses six points of commonality between the two situations. It is pointed out that the stop layer mechanism can be regarded as a direct reversal of the reconnection process.
-
Journal articleSherlock M, Rozmus W, Hill EG, et al., 2016,
Sherlock et al. Reply
, Physical Review Letters, Vol: 116, ISSN: 1079-7114
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.
Publications Archive
View the ISP Publications Archive