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  • Conference paper
    Aggarwal KM, Keenan FP, Rose SJ, 2001,

    Electron impact excitation of Al XIII: Collision strengths and rate coefficients

    , ISSN: 1155-4339

    Collision strengths for transitions among the n = 5 levels of Al XIII have been computed in the LS coupling scheme using the R-matrix code. All partial waves with angular momentum L ≤ 45 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths have been computed at energies below 220.0 Ryd, and effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are calculated over a wide temperature range of 4.40 ≤ log Te ≤ 6.0 K.
  • Conference paper
    Beg FN, Lebedev SV, Bland SN, Chittenden JC, Dangor AE, Haines MGet al., 2001,

    Effect of resistivity on dynamics of the wire arrays

    , ISSN: 0730-9244

    We report on the implosion dynamics of single nickel and copper wire arrays on the MAGPIE generator with a 1.4 MA, 240 ns current pulse. Plasma formed from individual wires has a corecorona structure. In the nickel arrays, a core size of 75 μm is measured by x-ray radiography. The formation of precursor on axis takes place at about 150 ns. Initially the precursor plasma is stable but shows an m=1 instability later in time. The implosion of the array occurs later than that predicted by a 0-D model, indicating that a fraction of the current flows through the precursor plasma. Like aluminum and tungsten, the m=1 instability in the precursor plasma is not observed in the copper arrays, and the implosion time is in accordance with a 0-D model. This implies that the resistivity of the wires play an important role in the dynamics of the wire arrays. Detailed results will be presented.
  • Conference paper
    Lebedev SV, Chittenden JP, Beg FN, Bland SN, Ciardi A, Ampleford D, Hughes S, Haines MGet al., 2001,

    Radiatively cooled supersonic plasma jets generated in wire array Z-pinches

    , ISSN: 0730-9244

    We will present experiments on the generation of a highly supersonic plasma jet by a convergent precursor plasma flow, produced by electrodynamic acceleration of plasma in a conical array of fine metallic wires (a modification of the wire array Z-pinch). Stagnation of the plasma flow on the axis of symmetry forms a standing conical shock, which effectively collimates the flow in the axial direction. The use of different materials (Al, Fe and W) show that a highly supersonic (M∼20) and a well-collimated jet is generated when the radiative cooling rate of the plasma is significant. The interaction of this jet with different plasma targets is used for studies of hydrodynamic instabilities in decelerated plasma flow and the experimental results will be presented. The study of collisionless interpenetration of colliding plasmas is also possible in this system. Scaling of the jet parameters with the drive current from the present 1MA level will be discussed.
  • Conference paper
    Lebedev SV, Beg FN, Bland SN, Chittenden JP, Haines MGet al., 2001,

    Implosions of wire arrays with mixed materials and wire diameters

    , ISSN: 0730-9244

    The results of experiments on the MAGPIE generator (1.4 MA, 240ns) with single wire arrays composed from wires of two different materials (e.g. W and Al) or from wires of different diameters will be presented. The wires are placed in an array alternately on the same diameter, and this configuration of the array is used to investigate effects of material or wire diameter on the division of current between the wires. It was found that in a 32 Al / W mixed wire array, the Al wires (16 × 155m diameter) implode significantly earlier than W wires (16 × 55m diameter), despite the fact that mass per unit length was the same for both materials. This presumably occurs due to a higher conductivity of plasma formed from Al wires, in which most of the total current flows during the first ∼70% of the implosion time. The difference in the implosion times of the two parts of the mixed wire arrays allows us to separate experimentally the contributions to the X-ray pulse from the kinetic energy and from the compression of the plasma by the magnetic field. This also suggests a possibility to control the shape of the x-ray pulse, in a way similar to the nested wire arrays operating in a current switching mode.
  • Conference paper
    Chittenden JP, Lebedev SV, Jennings C, Bland SNet al., 2001,

    Three-dimensional modeling of the implosion phase of array Z pinches

    , ISSN: 0730-9244

    A 3D resistive magneto-hydrodynamic model is used to simulate a single wire in a cylindrical wire array undergoing implosion. As with 2D x-y plane calculations, the persistence of a cold dense wire core results in the injection of radial streams of plasma into the interior of the array prior to implosion. Variations in the mass per unit length along the wire means that some regions of the wire core run out of material and begin imploding towards the array axis earlier than others causing the residual wire core to break up. Rather than attempt to flow across the breaks in the wire plasma, the current flows along the first straight axial path, which is now inside the array. The process of "wire breaking" thus allows the full generator current to bypass the wire cores and be switched directly onto the outside of the radial plasmas streams. The ensuing implosion is then similar to the slug-like or snowplough-like implosion of a uniform fill pinch, in this case having significant axial modulation but little Rayleigh-Taylor instability growth. The origins and structure of the pinch emissions are therefore radically different to those predicted by 2D(r-z) MHD simulations of imploding shells. Simulations of the final stages of implosion may however still be possible using 2D(r-z) models provided appropriate initial conditions are used and examples of this are presented. Comparison of the 3D and 2D results with diagnostic images from the implosion phase of wire arrays on the MAGPIE generator at Imperial College and the SATURN and Z generators at Sandia National Laboratory are presented.
  • Conference paper
    Lebedev SV, Beg FN, Bland SN, Chittenden JP, Dangor AE, Haines MG, Zakaullah M, Pikuz SA, Shelkovenko TA, Hammer DAet al., 2001,

    X-ray backlighting of wire array <i>Z</i>-pinch implosions using <i>X</i> pinch

    , 13th Topical Conference on High-Temperature Plasma diagnostics, Publisher: AMER INST PHYSICS, Pages: 671-673, ISSN: 0034-6748
  • Conference paper
    Phillips ME, Keenan FP, Rose SJ, Botha GJJ, Foord ME, Heeter RF, Ferland GJet al., 2001,

    Photoionized plasma calculations using laboratory and astrophysical models

    , Photoionized Plasmas 2000 Conference, Publisher: ASTRONOMICAL SOC PACIFIC, Pages: 123-126
  • Conference paper
    Greenaway MW, Proud WG, Field JE, Goveas SG, Drake RCet al., 2001,

    The effect of surface finish on the high power transmission characteristics of fused-silica optical fibres

    , 32nd Annual Boulder Damage Symposium on Optical Materials for High-Power Lasers, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, Pages: 599-607, ISSN: 0277-786X
  • Conference paper
    Gifford MJ, Greenaway MW, Proud WG, Field JEet al., 2001,

    Properties of ultrafine energetic materials

    , 4th International Autumn Seminar on Propellants, Explosives and Pyrotechnics, Publisher: CHINA SCIENCE TECHNOLOGY PRESS, Pages: 3-11
  • Conference paper
    Greenaway MW, Gifford MJ, Proud WG, Field JEet al., 2001,

    Laser-driven flyer plate initiation of explosives

    , 4th International Autumn Seminar on Propellants, Explosives and Pyrotechnics, Publisher: CHINA SCIENCE TECHNOLOGY PRESS, Pages: 451-456
  • Journal article
    Pikuz SA, Shelkovenko TA, Romanova VM, Sinars DB, Hammer DA, Bland SN, Lebedev SVet al., 2001,

    X pinch as a source for X-ray radiography

    , NUKLEONIKA, Vol: 46, Pages: 21-25, ISSN: 0029-5922
  • Conference paper
    Murray NH, Proud WG, 2001,

    Measurement of lateral stress and spall strength in ceramics

    , International Conference on Fundamental Issues and Applications of Shock-Wave and High-Strain-Rate Phenomena (EXPLOMET 2000), Publisher: ELSEVIER SCIENCE BV, Pages: 151-156
  • Conference paper
    Woolsey NC, Ali YA, Evans R, Grundy RAD, Peschte SJ, Carolan P, Conway N, Dendy RO, Helander P, McClements KG, Kirk JG, Norreys PA, Notley MM, Rose SJet al., 2001,

    Supernova remnant simulation experiments on VULCAN.

    , 26th European Conference on Laser Interactions with Matter (ECLIM 2000), Publisher: SPIE-INT SOC OPTICAL ENGINEERING, Pages: 484-491, ISSN: 0277-786X
  • Journal article
    Burren CP, Woods KA, Rose SJ, Tauber M, Price DA, Heinrich U, Gilli G, Razzaghy-Azar M, Al-Ashwal A, Crock PA, Rochiccioli P, Yordam N, Ranke MB, Chatelain PG, Preece MA, Rosenfeld RG, Savage MOet al., 2001,

    Clinical and endocrine characteristics in atypical and classical growth hormone insensitivity syndrome

    , HORMONE RESEARCH, Vol: 55, Pages: 125-130, ISSN: 0301-0163
  • Journal article
    Norreys PA, Allott R, Clarke RJ, Collier J, Neely D, Rose SJ, Zepf M, Santala M, Bell AR, Krushelnick K, Dangor AE, Woolsey NC, Evans RG, Habara H, Norimatsu T, Kodama Ret al., 2000,

    Experimental studies of the advanced fast ignitor scheme

    , PHYSICS OF PLASMAS, Vol: 7, Pages: 3721-3726, ISSN: 1070-664X
  • Journal article
    Lebedev SV, Beg FN, Bland SN, Chittenden JP, Dangor AE, Haines MG, Pikuz SA, Shelkovenko TAet al., 2000,

    Effect of core-corona plasma structure on seeding of instabilities in wire array <i>Z</i> pinches

    , PHYSICAL REVIEW LETTERS, Vol: 85, Pages: 98-101, ISSN: 0031-9007
  • Journal article
    Walley SM, Balzer JE, Proud WG, Field JEet al., 2000,

    Response of thermites to dynamic high pressure and shear

    , PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 456, Pages: 1483-1503, ISSN: 1364-5021
  • Journal article
    Batani D, Davies JR, Bernardinello A, Pisani F, Koenig M, Hall TA, Ellwi S, Norreys P, Rose S, Djaoui A, Neely Det al., 2000,

    Explanations for the observed increase in fast electron penetration in laser shock compressed materials

    , PHYSICAL REVIEW E, Vol: 61, Pages: 5725-5733, ISSN: 1539-3755
  • Conference paper
    Haines MG, Lebedev SV, Chittenden JP, Beg FN, Bland SN, Dangor AEet al., 2000,

    The past, present, and future of <i>Z</i> pinches

    , 41st Annual Meeting of the Division of Plasma Physics of the American-Physical-Society, Publisher: AIP Publishing, Pages: 1672-1680, ISSN: 1070-664X
  • Journal article
    Walley SM, Proud WG, Rae PJ, Field JEet al., 2000,

    Comparison of two methods of measuring the rapid temperature rises in split Hopkinson bar specimens

    , REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 71, Pages: 1766-1771, ISSN: 0034-6748
  • Journal article
    Chittenden JP, Lebedev SV, Ruiz-Camacho J, Beg FN, Bland SN, Jennings CA, Bell AR, Haines HG, Pikuz SA, Shelkovenko TA, Hammer DAet al., 2000,

    Plasma formation in metallic wire Z pinches

    , PHYSICAL REVIEW E, Vol: 61, Pages: 4370-4380, ISSN: 1539-3755
  • Journal article
    Aggarwal KM, Norrington PH, Bell KL, Keenan FP, Pert GJ, Rose SJet al., 2000,

    Radiative rates for allowed transitions in Ni-like Nd, Sm, Eu, Ta, and W

    , ATOMIC DATA AND NUCLEAR DATA TABLES, Vol: 74, Pages: 157-255, ISSN: 0092-640X
  • Journal article
    Lebedev SV, Aliaga-Rossel R, Bland SN, Chittenden JP, Dangor AE, Haines MG, Zakaullah Met al., 2000,

    Two different modes of nested wire array <i>Z</i>-pinch implosions

    , PHYSICAL REVIEW LETTERS, Vol: 84, Pages: 1708-1711, ISSN: 0031-9007
  • Journal article
    Davidson SJ, Nazir K, Rose SJ, Smith R, Tallents GJet al., 2000,

    Short-pulse laser opacity measurements

    , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 65, Pages: 151-160, ISSN: 0022-4073
  • Journal article
    Beer ME, Patel PK, Rose SJ, Wark JSet al., 2000,

    Calculations of the modal photon densities and gain in a K/Cl resonantly photopumped X-ray laser

    , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 65, Pages: 71-81, ISSN: 0022-4073
  • Journal article
    Patel PK, Wolfrum E, Renner O, Loveridge A, Allott R, Neely D, Rose SJ, Wark JSet al., 2000,

    X-ray line reabsorption in a rapidly expanding plasma

    , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 65, Pages: 429-439, ISSN: 0022-4073
  • Journal article
    Rose SJ, 2000,

    The inclusion of Compton scattering in line radiation escape factors

    , JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER, Vol: 65, Pages: 471-475, ISSN: 0022-4073
  • Journal article
    Batani D, Davies JR, Bernardinello A, Pisani F, Koenig M, Hall TA, Ellwi S, Norreys P, Rose S, Djaoui A, Neely Det al., 2000,

    Explanations for the observed increase in fast electron penetration in laser shock compressed materials

    , Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol: 61, Pages: 5725-5733, ISSN: 1063-651X

    We analyze recent experimental results on the increase of fast electron penetration in shock compressed plastic [Phys. Rev. Lett. 81, 1003 (1998)]. It is explained by a combination of stopping power and electric field effects, which appear to be important even at laser intensities as low as [Formula Presented] An important conclusion is that fast electron induced heating must be taken into account, changing the properties of the material in which the fast electrons propagate. In insulators this leads to a rapid insulator to conductor phase transition. © 2000 The American Physical Society.
  • Journal article
    Haines MG, Lebedev SV, Chittenden JP, Beg FN, Bland SN, Dangor AEet al., 2000,

    The past, present, and future of [formula omitted] pinches

    , Physics of Plasmas, Vol: 7, Pages: 1672-1680, ISSN: 1070-664X

    The Z pinch is enjoying a renaissance as the world's most powerful yet efficient soft x-ray source which can energize large volume hohlraums for indirectly driven inertial confinement fusion. It has the advantages of being efficient and having high energy and power density. Its early history will be traced from the 18th century to the present day. The most notable feature of the Z pinch is its instability. The various regimes of stability analysis will be reviewed, including resistive and finite ion Larmor radius effects. Work in the last 10 years on single fibres, especially of cryogenic deuterium, gave neutrons that were of the same origin, namely, beam–plasma interactions, as reported by Kurchatov. The renaissance has come about through the implosion of arrays of fine wires. Research at Sandia National Laboratory has shown that by using more and finer wires, the x-ray radiation emitted at stagnation increased in power and decreased in pulse width. The understanding of these results has been advanced considerably by theory, simulation and smaller-scale, well diagnosed experiments showing the early uncorrelated [formula omitted] instabilities on each wire, the inward jetting of plasma to the axis, the global Rayleigh–Taylor instability and the mitigating effect of nested arrays. © 2000, American Institute of Physics. All rights reserved.
  • Journal article
    Chittenden JP, Lebedev SV, Ruiz-Camacho J, Beg FN, Bland SN, Jennings CA, Bell AR, Haines MG, Pikuz SA, Shelkovenko TA, Hammer DAet al., 2000,

    Plasma formation in metallic wire Z pinches

    , Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol: 61, Pages: 4370-4380, ISSN: 1063-651X

    Plasma formation in metallic wire Z pinches is modeled using a two-dimensional resistive magnetohydrodynamics code. Modified Thomas-Fermi equations of state and dense plasma transport coefficients allow the phase transitions from solid to plasma to be approximated. Results indicate the persistence of a two-component structure with a cold, dense core embedded within a much hotter, low density, [Formula Presented] unstable corona. Extensive benchmark testing against data from a number of single-wire experiments is presented. Artificial laser schlieren and x-ray back-lighting images generated from the code data are compared directly to experimental results. The results were found to be insensitive to inaccuracies in the equations of state and transport coefficients. Simulations of individual wires in a wire array show different behavior to that observed experimentally due to the absence of three-dimensional effects. Simulations with similar conditions to wires in an array show a general trend in the plasma structure at start of implosion from discrete wires with large [Formula Presented] perturbation amplitudes to partially merged wires with smaller perturbation amplitudes as the number of wires is increased. Results for a wire number scan with aluminum wire arrays on the SATURN generator suggest that the observed sharp transition to high x-ray power at around 40 wires corresponds to a sharp decrease in [Formula Presented] perturbation amplitude and hence a sharp decrease in the seed perturbation for the Rayleigh-Taylor instability. © 2000 The American Physical Society.

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