35 results found
Hare JD, Lebedev SV, Suttle LG, et al., 2017, Formation and structure of a current sheet in pulsed-power driven magnetic reconnection experiments, Physics of Plasmas, Vol: 24, ISSN: 1070-664X
We describe magnetic reconnection experiments using a new, pulsed-powerdriven experimental platform in which the inflows are super-sonic butsub-Alfv\'enic.The intrinsically magnetised plasma flows are long lasting,producing a well-defined reconnection layer that persists over manyhydrodynamic time scales.The layer is diagnosed using a suite of highresolution laser based diagnostics which provide measurements of the electrondensity, reconnecting magnetic field, inflow and outflow velocities and theelectron and ion temperatures.Using these measurements we observe a balancebetween the power flow into and out of the layer, and we find that the heatingrates for the electrons and ions are significantly in excess of the classicalpredictions. The formation of plasmoids is observed in laser interferometry andoptical self-emission, and the magnetic O-point structure of these plasmoids isconfirmed using magnetic probes.
Walsh C, Chittenden JP, McGlinchey K, et al., 2017, Self-Generated magnetic fields in the stagnation phase of indirect-drive implosions on the national ignition facility, Physical Review Letters, Vol: 118, ISSN: 1079-7114
Three-dimensional extended-magnetohydrodynamic simulations of the stagnation phase of inertial confinement fusion implosion experiments at the National Ignition Facility are presented, showing self-generated magnetic fields over 10^4 T. Angular high mode-number perturbations develop large magnetic fields, but are localized to the cold, dense hot-spot surface, which is hard to magnetize. When low-mode perturbations are also present, the magnetic fields are injected into the hot core, reaching significant magnetizations, with peak local thermal conductivity reductions greater than 90%. However, Righi-Leduc heat transport effectively cools the hot spot and lowers the neutron spectra-inferred ion temperatures compared to the unmagnetized case. The Nernst effect qualitatively changes the results by demagnetizing the hot-spot core, while increasing magnetizations at the edge and near regions of large heat loss.
Hare JD, Suttle L, Lebedev SV, et al., 2017, Anomalous heating and plasmoid formation in a driven magnetic reconnection experiment, Physical Review Letters, Vol: 118, ISSN: 0031-9007
We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields (B=3 T), advected by supersonic, sub-Alfvénic carbon plasma flows (Vin=50 km/s), are brought together and mutually annihilate inside a thin current layer (δ=0.6 mm). Temporally and spatially resolved optical diagnostics, including interferometry, Faraday rotation imaging, and Thomson scattering, allow us to determine the structure and dynamics of this layer, the nature of the inflows and outflows, and the detailed energy partition during the reconnection process. We measure high electron and ion temperatures (Te=100 eV, Ti=600 eV), far in excess of what can be attributed to classical (Spitzer) resistive and viscous dissipation. We observe the repeated formation and ejection of plasmoids, consistent with the predictions from semicollisional plasmoid theory.
Suttle LG, Hare JD, Lebedev SV, et al., 2016, Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows, Physical Review Letters, Vol: 116, ISSN: 1079-7114
We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (Ti∼Z¯Te, with average ionization Z¯=7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.
Chittenden JP, Appelbe BD, Manke F, et al., 2016, Signatures of asymmetry in neutron spectra and images predicted by three-dimensional radiation hydrodynamics simulations of indirect drive implosions, Physics of Plasmas, Vol: 23, ISSN: 1089-7674
We present the results of 3D simulations of indirect drive inertial confinement fusion capsules driven by the “high-foot” radiation pulse on the National Ignition Facility. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium (DT) and deuterium-deuterium (DD) neutronspectra as well as primary and down scatteredneutronimages. Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutronspectra shift, width, and shape. Comparisons of primary and down scatteredimages highlight the lack of alignment between the neutron sources,scatter sites, and detector plane, which limits the ability to infer the ρr of the fuel from a down scattered ratio. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutronspectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.
Burdiak GC, Lebedev SV, Clayson T, et al., 2016, THE EFFECT OF MAGNETIC FIELD ORIENTATION ON THE STRUCTURE AND INTERACTION OF MAGNETISED BOW SHOCKS IN PULSED-POWER DRIVEN EXPERIMENTS, 43rd IEEE International Conference on Plasma Science (ICOPS), Publisher: IEEE
Bott-Suzuki SC, Bendixsen LSC, Cordaro SW, et al., 2015, Investigation of radiative bow-shocks in magnetically accelerated plasma flows, PHYSICS OF PLASMAS, Vol: 22, ISSN: 1070-664X
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.
Ampleford DJ, Hansen SB, Jennings CA, et al., 2015, Scaling and enhancement of non-thermal line emission on z to hν ∼ 22 kev
Mariscal D, McGuffey C, Valenzuela J, et al., 2014, Measurement of pulsed-power-driven magnetic fields via proton deflectometry, APPLIED PHYSICS LETTERS, Vol: 105, ISSN: 0003-6951
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
Ivanov VV, Anderson AA, Papp D, et al., 2014, UV Laser-Probing Diagnostics for the Dense Z Pinch, IEEE TRANSACTIONS ON PLASMA SCIENCE, Vol: 42, Pages: 1153-1162, ISSN: 0093-3813
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
Ivanov VV, Anderson AA, Papp D, et al., 2013, Current redistribution and generation of kinetic energy in the stagnated Z pinch, PHYSICAL REVIEW E, Vol: 88, ISSN: 1539-3755
Swadling GF, Lebedev SV, Niasse N, et al., 2013, Oblique shock structures formed during the ablation phase of aluminium wire array z-pinches, PHYSICS OF PLASMAS, Vol: 20, ISSN: 1070-6631
Taylor S, Appelbe B, Niasse NP, et al., 2013, Effect of perturbations on yield in ICF targets-4 pi 3D hydro simulations, IFSA 2011 - SEVENTH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS, Vol: 59, ISSN: 2100-014X
Ivanov VV, Chittenden JP, Mancini RC, et al., 2012, Investigation of plasma instabilities in the stagnated Z pinch, PHYSICAL REVIEW E, Vol: 86, ISSN: 1539-3755
Ivanov VV, Chittenden JP, Altemara SD, et al., 2011, Study of the Internal Structure and Small-Scale Instabilities in the Dense $Z$ Pinch, Phys. Rev. Lett., Vol: 107, Pages: 165002-165002
Pickworth LA, Bland SN, Lebedev SV, et al., 2011, Preliminary opacity experiments in dense high Z plasmas on the magpie facility, Pages: 1-1, ISSN: 0730-9244
Swadling GF, Lebedev SV, Bland SN, et al., 2011, End-on laser probing of the ablation phase of wire array z-pinch implosions on the magpie generator, Pages: 1-1, ISSN: 0730-9244
Niasse N, Chittenden J, 2011, Atomic model and synthetic diagnostics for large scale parallel simulations of wire array Z-pinches, Pages: 1-1, ISSN: 0730-9244
Niasse N, 2011, A simple Non-LTE model for Z-pinch simulations
Haas D, Bott S, Kim J, et al., 2011, Supersonic jet formation and propagation in x-pinches, Astrophysics and Space Science, Vol: 336, Pages: 33-40-33-40, ISSN: 0004-640X
Grunenwald J, Calamy H, Lassalle F, et al., 2010, Status on numerical MHD tools used to analyse wire array experiments at ceagramat for radiation effects and HEDP studies, Pages: 1-1, ISSN: 0730-9244
Swadling G, Lebedev S, Bland S, et al., 2010, Development of laser based diagnostics for the investigation of wire array Z-pinch dynamics on the MAGPIE generator, Pages: 1-1, ISSN: 0730-9244
Niasse N, Chittenden J, 2010, Development of a Non-LTE model for Z-pinch simulations
Calamy H, Loyen A, Zucchini F, et al., 2009, First results of radial array experiments in microsecond regime, Pages: 1-1, ISSN: 0730-9244
Chittenden JP, Niasse NP, Bland SN, et al., 2009, Recent advances in magneto-hydrodynamic modeling of wire array Z-pinches, Pages: 1-1, ISSN: 0730-9244
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.