Publications
114 results found
Cotelo M, Velarde P, de la Varga AG, et al., 2015, Simulation of radiative shock waves in Xe of last PALS experiments, HIGH ENERGY DENSITY PHYSICS, Vol: 17, Pages: 68-73, ISSN: 1574-1818
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- Citations: 9
Larour J, Singh RL, Stehle C, et al., 2015, Optimization of an electromagnetic generator for strong shocks in low pressure gas, HIGH ENERGY DENSITY PHYSICS, Vol: 17, Pages: 129-134, ISSN: 1574-1818
Chaulagain U, Stehle C, Larour J, et al., 2015, Structure of a laser-driven radiative shock, HIGH ENERGY DENSITY PHYSICS, Vol: 17, Pages: 106-113, ISSN: 1574-1818
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- Citations: 17
Burdiak GC, Lebedev SV, Harvey-Thompson AJ, et 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
Ampleford DJ, Bland SN, Jennings CA, et 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
Swadling GF, Hall GN, Lebedev SV, et al., 2015, Commissioning of a Rotated Wire Array Configuration for Improved Diagnostic Access, IEEE TRANSACTIONS ON PLASMA SCIENCE, Vol: 43, Pages: 2503-2508, ISSN: 0093-3813
Veloso F, Munoz-Cordovez G, Donoso-Tapia L, et al., 2015, Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology, Physics of Plasmas, Vol: 22, ISSN: 1089-7674
The dynamics of ablation streams and precursor plasma in cylindrical wire array Z-pinches under temporal variations of the global magnetic field topology is investigated through experiments and numerical simulations. The wire arrays in these experiments are modified by replacing a pair of consecutive wires with wires of a larger diameter. This modification leads to two separate effects, both of which impact the dynamics of the precursor plasma; firstly, current is unevenly distributed between the wires and secondly, the thicker wires take longer to fully ablate. The uneven distribution of current is evidenced in the experiments by the drift of the precursor off axis due to a variation in the global magnetic field topology which modifies the direction of the ablation streams tracking the precursor position. The variation of the global magnetic field due to the presence of thick wires is studied with three-dimensional magnetohydrodynamic (MHD) simulations, showing that the global field changes from the expected toroidal field to a temporally variable topology after breakages appear in the thin wires. This leads to an observed acceleration of the precursor column towards the region closer to the thick wires and later, when thick wires also present breakages, it continues moving away from the original array position as a complicated and disperse object subject to MHD instabilities.
Swadling GF, Lebedev SV, Harvey-Thompson AJ, et 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
Rodriguez R, Espinosa G, Gil JM, et al., 2015, Microscopic properties of xenon plasmas for density and temperature regimes of laboratory astrophysics experiments on radiative shocks, PHYSICAL REVIEW E, Vol: 91, ISSN: 2470-0045
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- Citations: 6
Swadling GF, Lebedev SV, Harvey-Thompson AJ, et al., 2015, Erratum: Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows [Phys. Rev. Lett. 113, 035003 (2014)], Physical Review Letters, Vol: 114, ISSN: 0031-9007
Burdiak GC, Lebedev SV, Suzuki-Vidal F, et 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.
Bennett MJ, Lebedev SV, Hall GN, et al., 2015, Formation of radiatively cooled, supersonically rotating, plasma flows in Z-pinch experiments: Towards the development of an experimental platform to study accretion disk physics in the laboratory, High Energy Density Physics, Vol: 17, Pages: 63-67, ISSN: 1878-0563
We present data from the first Z-pinch experiments aiming to simulate aspects of accretion disk physics in the laboratory. Using off axis ablation flows from a wire array z-pinch we demonstrate the formation of a supersonically (M ∼ 2) rotating hollow plasma cylinder of height ∼4 mm and radius 2 mm. Using a combination of diagnostics we measure the rotation speed (∼60 kms−1), electron density (1019 cm−3), ion temperature (Ti ∼ 60 eV) and the product of electron temperature and average ionisation (ZTe ∼ 150 to 200 eV). Using these parameters we calculate the Reynolds number for the plasma on the order 105 and magnetic Reynolds number as 10 – 100. The plasma flow is maintained for 150 ns, corresponding to one rotation period, which should allow for studying fast instabilities which develop on this time-scale.
Suzuki-Vidal F, 2015, PLASMA PHYSICS How to spark a field, NATURE PHYSICS, Vol: 11, Pages: 98-99, ISSN: 1745-2473
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- Citations: 3
Hare JD, Lebedev SV, Bennett M, et al., 2015, Photo-ionisation of gas by x-rays from a wire array z-pinch
Burdiak GC, Lebedev SV, Bland S, et al., 2015, Radiative precursors driven by converging blast waves in noble gases
Swadling GF, Lebedev SV, Burdiak G, et al., 2015, Thomson scattering measurements of supersonic tungsten plasma flow interpenetration in wire array z-pinches
Veloso F, Donoso L, Swadling G, et al., 2015, Effects of uneven mass distribution on plasma dynamics in cylindrical wire array Z-pinches, 15th Latin American Workshop on Plasma Physics (LAWPP) / 21st IAEA TM on Research Using Small Fusion Devices (RUSFD), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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- Citations: 1
Espinosa G, Gil JM, Rodriguez R, et al., 2014, Collisional-radiative simulations of a supersonic and radiatively cooled aluminum plasma jet, High Energy Density Physics, Vol: 17, Pages: 74-84, ISSN: 1878-0563
A computational investigation based on collisionaleradiative simulations of a supersonic and radiativelycooled aluminum plasma jet is presented. The jet, both in vacuum and in argon ambient gas, was producedon the MAGPIE (Mega Ampere Generator for Plasma Implosion Experiments) generator and isformed by ablation of an aluminum foil driven by a 1.4 MA, 250 ns current pulse in a radial foil Z-pinchconfiguration. In this work, population kinetics and radiative properties simulations of the jet in differenttheoretical approximations were performed. In particular, local thermodynamic equilibrium (LTE), nonLTEsteady state (SS) and non-LTE time dependent (TD) models have been considered. This study allowsus to make a convenient microscopic characterization of the aluminum plasma jet.
Swadling GF, Lebedev SV, Hall GN, et 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
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- Citations: 51
Hall GN, Burdiak GC, Suttle L, et 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.
Swadling GF, Lebedev SV, Harvey-Thompson AJ, et al., 2014, Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows, PHYSICAL REVIEW LETTERS, Vol: 113, ISSN: 0031-9007
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- Citations: 21
Stehle C, Kozlova M, Larour J, et al., 2014, Reply on the comment of the paper "New probing techniques of radiative shocks", OPTICS COMMUNICATIONS, Vol: 318, Pages: 226-230, ISSN: 0030-4018
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- Citations: 1
Lebedev SV, Suttle L, Swadling GF, et al., 2014, The formation of reverse shocks in magnetized high energy density supersonic plasma flows, PHYSICS OF PLASMAS, Vol: 21, ISSN: 1070-664X
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- Citations: 30
Burdiak GC, Lebedev SV, Harvey-Thompson AJ, et al., 2014, Radiative precursors driven by converging blast waves in noble gases, PHYSICS OF PLASMAS, Vol: 21, ISSN: 1070-664X
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- Citations: 6
Stehle C, Lefevre R, Chaulagain U, et al., 2014, Critical Components for XUV Probing of Laser Driven Shocks, 13th International Conference on X-Ray Lasers (ICXRL), Publisher: SPRINGER-VERLAG BERLIN, Pages: 239-242, ISSN: 0930-8989
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- Citations: 1
Kozlova M, Nejdl J, Krus M, et al., 2014, Characterization of Zn X-Ray Laser at PALS Centre, Its Applications in Dense Plasma Probing and Astrophysics, 13th International Conference on X-Ray Lasers (ICXRL), Publisher: SPRINGER-VERLAG BERLIN, Pages: 151-159, ISSN: 0930-8989
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- Citations: 3
Bennett MJ, Lebedev SV, Hall GN, et al., 2014, Rotating Plasma Disks in Dense Z-pinch Experiments, 9th International Conference on Dense Z Pinches, Publisher: AMER INST PHYSICS, Pages: 71-75, ISSN: 0094-243X
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- Citations: 1
Suzuki-Vidal F, Lebedev SV, Ciardi A, et al., 2014, Laboratory Astrophysics Experiments with Magnetically Driven Plasma Jets, 15th International Congress on Plasma Physics (ICPP) / 13th Latin American Workshop on Plasma Physics (LAWPP), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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- Citations: 2
Swadling GF, Lebedev SV, Harvey-Thompson AJ, et al., 2014, Calculation of Thomson Scattering Spectral Fits for Interpenetrating Flows, 9th International Conference on Dense Z Pinches, Publisher: AMER INST PHYSICS, Pages: 118-121, ISSN: 0094-243X
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- Citations: 2
Suzuki Vidal F, Patankar S, Lebedev SV, et al., 2013, Observation of energetic protons trapped in laboratory magnetic-tower jets, New Journal of Physics, Vol: 15, ISSN: 1367-2630
Preliminary results of the self-emission of charged particles frommagnetically driven plasma jets has been investigated. The jets were launchedand driven by a toroidal magnetic field generated by introducing a ∼1.4 MA,250 ns electrical current pulse from the MAGPIE generator into a radialwire array. This configuration has shown to reproduce some aspects of theastrophysical magnetic-tower jet launching model, in which a jet is collimatedby a toroidal magnetic field inside a magnetic cavity. The emission of ions andprotons from the plasma was recorded onto Columbia Resin 39 plates using timeintegratedpinhole cameras. In addition a fly-eye camera, an array of 25–496cylindrical apertures allowed estimating the location of the ion emitting source.The results show the ion emission comes from both the jet and its surroundingmagnetic cavity, with the emission extending to a height of at least ∼9 cm fromthe initial position of the wires. The emission of ions is consistent with the dynamics of the jet obtained from time-resolved imaging diagnostics, i.e. opticallaser probing and self-emission of the plasma in the extreme ultra-violet. Thesepreliminary results suggest the ions are trapped inside the cavity due to the strongtoroidal magnetic field which drives the jet. In addition these studies providefirst estimates of the energy and fluence of protons for future laser-driven protonprobing diagnostics aimed at measuring the magnetic field in these experiments.
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