liu.seSearch for publications in DiVA
Endre søk
Begrens søket
12 1 - 50 of 81
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Ahmed, Hamad
    et al.
    Queen's University Belfast, UK.
    Dieckmann, Mark Eric
    Queen's University Belfast, UK.
    Romagnani, Lorenzo
    Ecole Polytechnique, Palaiseau, France.
    Doria, Domenico
    Queen's University Belfast, UK.
    Sarri, Gianluca
    Queen's University Belfast.
    Cherchez, Mirelie
    University of Düsseldorf, Germany.
    Ianni, E.
    Universita di Pisa, Italy.
    Kourakis, Ioannis
    Queen's University Belfast, UK.
    Giesecke, Anna Lena
    University of Düsseldorf, Germany.
    Notley, Margaret
    Rutherford Appleton Laboratory, Chilton, Oxfordshire, UK.
    Prasad, R.
    Queen's University Belfast, UK.
    Quinn, Kevin
    Queen's University Belfast, UK.
    Willi, Oswald
    University of Düsseldorf, Germany.
    Borghesi, Marco
    Queen's University Belfast, UK.
    Time-Resolved Characterization of the Formation of a Collisionless Shock2013Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, nr 20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the temporally and spatially resolved detection of the precursory stages that lead to the formation of an unmagnetized, supercritical collisionless shock in a laser-driven laboratory experiment. The measured evolution of the electrostatic potential associated with the shock unveils the transition from a current free double layer into a symmetric shock structure, stabilized by ion reflection at the shock front. Supported by a matching particle-in-cell simulation and theoretical considerations, we suggest that this process is analogous to ion reflection at supercritical collisionless shocks in supernova remnants.

  • 2.
    Ahmed, Hamad
    et al.
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Doria, Domenico
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Sarri, Gianluca
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Romagnani, Lorenzo
    LULI, École Polytechnique, CNRS, CEA, UPMC, Palaiseau, France.
    Bret, Antoine
    ETSI Industriales, Universidad Castilla La Mancha, E-13 071 Ciudad Real, Spain.
    Cerchez, M
    Institute for Laser and Plasma Physics, University of Düsseldorf, Germany.
    Giesecke, AL
    Institute for Laser and Plasma Physics, University of Düsseldorf, Germany.
    Ianni, E
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Kar, Satya
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Notley, Margaret
    Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK.
    Prasad, R
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Quinn, Kevin
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Willi, Oswald
    Institute for Laser and Plasma Physics, University of Düsseldorf, Germany.
    Borghesi, Marco
    Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN, UK.
    Experimental Observation of Thin-shell Instability in a Collisionless Plasma2017Inngår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 834, nr 2, artikkel-id L21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.

  • 3.
    Brenning, Nils
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden; University of Paris Saclay, France.
    Gudmundsson, J. T.
    KTH Royal Institute Technology, Sweden; University of Paris Saclay, France; University of Iceland, Iceland.
    Lundin, D.
    University of Paris Saclay, France.
    Minea, T.
    University of Paris Saclay, France.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    The role of Ohmic heating in dc magnetron sputtering2016Inngår i: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, nr 6, artikkel-id 065024Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sustaining a plasma in a magnetron discharge requires energization of the plasma electrons. In this work, Ohmic heating of electrons outside the cathode sheath is demonstrated to be typically of the same order as sheath energization, and a simple physical explanation is given. We propose a generalized Thornton equation that includes both sheath energization and Ohmic heating of electrons. The secondary electron emission yield gamma(SE) is identified as the key parameter determining the relative importance of the two processes. For a conventional 5 cm diameter planar dc magnetron, Ohmic heating is found to be more important than sheath energization for secondary electron emission yields below around 0.1.

  • 4.
    Brenning, Nils
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden; University of Paris Saclay, France.
    Gudmundsson, J. T.
    KTH Royal Institute Technology, Sweden; University of Paris Saclay, France; University of Iceland, Iceland.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Petty, T. J.
    University of Paris Saclay, France.
    Minea, T.
    University of Paris Saclay, France.
    Lundin, D.
    University of Paris Saclay, France.
    A unified treatment of self-sputtering, process gas recycling, and runaway for high power impulse sputtering magnetrons2017Inngår i: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 26, nr 12, artikkel-id 125003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The combined processes of self-sputter (SS)-recycling and process gas recycling in high power impulse magnetron sputtering (HiPIMS) discharges are analyzed using the generalized recycling model (GRM). The study uses experimental data from discharges with current densities from the direct current magnetron sputtering range to the HiPIMS range, and using targets with self-sputter yields Y-SS from approximate to 0.1 to 2.6. The GRM analysis reveals that, above a critical current density of the order of J(crit) approximate to 0.2 A cm(-2), a combination of self-sputter recycling and gas-recycling is generally the case. The relative contributions of these recycling mechanisms, in turn, influence both the electron energy distribution and the stability of the discharges. For high self-sputter yields, above Y-SS approximate to 1, the discharges become dominated by SS-recycling, contain few hot secondary electrons from sheath energization, and have a relatively low electron temperature T-e. Here, stable plateau values of the discharge current develop during long pulses, and these values increase monotonically with the applied voltage. For low self-sputter yields, below Y-SS approximate to 0.2, the discharges above J(crit) are dominated by process gas recycling, have a significant sheath energization of secondary electrons and a higher T-e, and the current evolution is generally less stable. For intermediate values of YSS the discharge character gradually shifts between these two types. All of these discharges can, at sufficiently high discharge voltage, give currents that increase rapidly in time. For such cases we propose that a distinction should be made between unlimited runaway and limited runaway: in unlimited runaway the current can, in principle, increase without a limit for a fixed discharge voltage, while in limited runaway it can only grow towards finite, albeit very high, levels. For unlimited runway Y-SS amp;gt; 1 is found to be a necessary criterion, independent of the amount of gas-recycling in the discharge.

  • 5.
    Bret, Antoine
    et al.
    Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain.
    Dieckmann, Mark E
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Hierarchy of instabilities for two counter-streaming magnetized pair beams: Influence of field obliquity2017Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, nr 6, artikkel-id 062105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hierarchy of unstable modes when two counter-streaming pair plasmas interact over a flow-aligned magnetic field has been recently investigated [Phys. Plasmas 23, 062122 (2016)]. The analysis is here extended to the case of an arbitrarily tilted magnetic field. The two plasma shells are initially cold and identical. For any angle θ ∈ [0, π/2] between the field and the initial flow, the hierarchy of unstable modes is numerically determined in terms of the initial Lorentz factor of the shells γ0, and the field strength as measured by a parameter denoted σ. For θ = 0, four different kinds of mode are likely to lead the linear phase. The hierarchy simplifies for larger θ's, partly because the Weibel instability can no longer be cancelled in this regime. For θ > 0.78 (44°) and in the relativistic regime, the Weibel instability always govern the interaction. In the non-relativistic regime, the hierarchy becomes θ-independent because the interaction turns to be field-independent. As a result, the two-stream instability becomes the dominant one, regardless of the field obliquity.

  • 6.
    Bret, Antoine
    et al.
    Universidad de Castilla-La Mancha, Spain.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    How large can the electron to proton mass ratio be in particle-in-cell simulations of unstable systems?2010Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 3, s. 032109-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Particle-in-cell simulations are widely used as a tool to investigate instabilities that develop between a collisionless plasma and beams of charged particles. However, even on contemporary supercomputers, it is not always possible to resolve the ion dynamics in more than one spatial dimension with such simulations. The ion mass is thus reduced below 1836 electron masses, which can affect the plasma dynamics during the initial exponential growth phase of the instability and during the subsequent nonlinear saturation. The goal of this article is to assess how far the electron to ion mass ratio can be increased, without changing qualitatively the physics. It is first demonstrated that there can be no exact similarity law, which balances a change in the mass ratio with that of another plasma parameter, leaving the physics unchanged. Restricting then the analysis to the linear phase, a criterion allowing to define a maximum ratio is explicated in terms of the hierarchy of the linear unstable modes. The criterion is applied to the case of a relativistic electron beam crossing an unmagnetized electron-ion plasma.

  • 7.
    Bret, Antoine
    et al.
    ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    On the proton to electron mass ratio in particle-in-cell simulations2011Inngår i: Europhysics conference abstracts, 2011, s. O4.310-1-O4.310-4Konferansepaper (Fagfellevurdert)
  • 8.
    Bret, Antoine
    et al.
    ETSI Ind Univ Castilla-La Mancha.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Gremillet, Laurent
    CEA, DAM, DIF, 91297 Arpajon, France.
    Recent progresses in relativistic beam-plasma instability theory2010Inngår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 28, nr 11, s. 2127-2132Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Beam-plasma instabilities are a key physical process in many astrophysical phenomena. Within the fireball model of Gamma ray bursts, they first mediate a relativistic collisionless shock before they produce upstream the turbulence needed for the Fermi acceleration process. While non-relativistic systems are usually governed by flow-aligned unstable modes, relativistic ones are likely to be dominated by normally or even obliquely propagating waves. After reviewing the basis of the theory, results related to the relativistic kinetic regime of the poorly-known oblique unstable modes will be presented. Relevant systems besides the well-known electron beam-plasma interaction are presented, and it is shown how the concept of modes hierarchy yields a criterion to assess the proton to electron mass ratio in Particle in cell simulations.

  • 9.
    Bret, Antoine
    et al.
    ETSI Ind Univ Castilla-La Mancha.
    Gremillet, Laurent
    CEA, DAM, DIF, 91297 Arpajon, France.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Multidimensional electron beam-plasma instabilities in the relativistic regime2010Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, nr 12, s. 120501-1-120501-36Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    The interest in relativistic beam-plasma instabilities has been greatly rejuvenated over the past two decades by novel concepts in laboratory and space plasmas. Recent advances in this long-standing field are here reviewed from both theoretical and numerical points of view. The primary focus is on the two-dimensional spectrum of unstable electromagnetic waves growing within relativistic, unmagnetized, and uniform electron beam-plasma systems. Although the goal is to provide a unified picture of all instability classes at play, emphasis is put on the potentially dominant waves propagating obliquely to the beam direction, which have received little attention over the years. First, the basic derivation of the general dielectric function of a kinetic relativistic plasma is recalled. Next, an overview of two-dimensional unstable spectra associated with various beam-plasma distribution functions is given. Both cold-fluid and kinetic linear theory results are reported, the latter being based on waterbag and Maxwell–Jüttner model distributions. The main properties of the competing modes (developing parallel, transverse, and oblique to the beam) are given, and their respective region of dominance in the system parameter space is explained. Later sections address particle-in-cell numerical simulations and the nonlinear evolution of multidimensional beam-plasma systems. The elementary structures generated by the various instability classes are first discussed in the case of reduced-geometry systems. Validation of linear theory is then illustrated in detail for large-scale systems, as is the multistaged character of the nonlinear phase. Finally, a collection of closely related beam-plasma problems involving additional physical effects is presented, and worthwhile directions of future research are outlined.

  • 10.
    Bret, Antoine
    et al.
    ETSI Industriales, Universidad de Castilla-La Mancha, Ciudad Real, Spain.
    Pe'er, Asaf
    Physics Department, University College Cork, Cork, Ireland.
    Sironi, Lorenzo
    Department of Astronomy, Columbia University, New York, NY, USA.
    Dieckmann, Mark E
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Narayan, Ramesh
    Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA.
    Departure from MHD prescriptions in shock formation over a guiding magnetic field2017Inngår i: Laser and particle beams (Print), ISSN 0263-0346, E-ISSN 1469-803X, Vol. 35, s. 513-519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In plasmas where the mean-free-path is much larger than the size of the system, shock waves can arise with a front much shorter than the mean-free path. These so-called "collisionless shocks" are mediated y collective plasma interactions. Studies conducted so far on these shocks found that although binary collisions are absent, the distribution functions are thermalized downstream by scattering on the fields, so that magnetohydrodynamic prescriptions may apply. Here we show a clear departure from this pattern in the case of Weibel shocks forming over a flow-aligned magnetic field. A micro-physical analysis of the particle motion in the Weibel filaments shows how they become unable to trap the flow in the presence of too strong a field, inhibiting the mechanism of shock formation. Particle-in-cell simulations confirm these results.

  • 11.
    Bret, Antoine
    et al.
    ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain.
    Stockem Novo, Anne
    Fakultät fuer Physik und Astronomie, Ruhr-Universität Bochum, 44780 Bochum, Germany.
    Narayan, Ramesh
    Harvard-Smithsonian Center for Astrophysics, Harvard University, Cambridge, MA 02138, USA.
    Ruyer, Charles
    High Energy Density Science Division, SLAC National Accelerator Lab., Menlo Park, CA 94025, USA.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Silva, Luis O
    GoLP/Instituto de Plasmas e Fusão Nuclear – Laboratório Associado, Instituto Superior Técnico, Lisboa, Portugal.
    Theory of the formation of a collisionless Weibel shock: pair vs. electron/proton plasmas2016Inngår i: Laser and particle beams (Print), ISSN 0263-0346, E-ISSN 1469-803X, Vol. 34, nr 2, s. 362-367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Collisionless shocks are shocks in which the mean-free path is much larger than the shock front. They are ubiquitous in astrophysics and the object of much current attention as they are known to be excellent particle accelerators that could be the key to the cosmic rays enigma. While the scenario leading to the formation of a fluid shock is well known, less is known about the formation of a collisionless shock. We present theoretical and numerical results on the formation of such shocks when two relativistic and symmetric plasma shells (pair or electron/proton) collide. As the two shells start to interpenetrate, the overlapping region turns Weibel unstable. A key concept is the one of trapping time τp, which is the time when the turbulence in the central region has grown enough to trap the incoming flow. For the pair case, this time is simply the saturation time of the Weibel instability. For the electron/proton case, the filaments resulting from the growth of the electronic and protonic Weibel instabilities, need to grow further for the trapping time to be reached. In either case, the shock formation time is 2τp in two-dimensional (2D), and 3τp in 3D. Our results are successfully checked by particle-in-cell simulations and may help designing experiments aiming at producing such shocks in the laboratory.

  • 12.
    Brodin, G.
    et al.
    Umeå University, Sweden.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    A new decay channel for upper-hybrid waves2016Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 91, nr 10, artikkel-id 104005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We look here at a three-wave interaction process involving only electrostatic waves in an electron plasma with stationary ions. Special attention is given to the case with an upper-hybrid wave as a pump wave, where a new decay channel is pointed out. The corresponding growth rate is calculated.

  • 13.
    Brodin, G.
    et al.
    Umeå University, Sweden.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    A simple electron plasma wave2017Inngår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 381, nr 11, s. 1033-1035Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Considering a class of solutions where the density perturbations are functions of time, but not of space, we derive a new exact large amplitude wave solution for a cold uniform electron plasma. This result illustrates that most simple analytical solutions can appear even if the density perturbations are large. (C) 2016 Elsevier B.V. All rights reserved.

  • 14.
    Brodin, G.
    et al.
    Umeå University, Sweden.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Nonlinear dynamics of a cold collisional electron plasma2017Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, nr 12, artikkel-id 124505Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the influence of collisions on the dynamics of a cold non-relativistic plasma. It is shown that even a comparatively small collision frequency can significantly change the large amplitude wave solution. Published by AIP Publishing.

  • 15.
    Brown, M. R.
    et al.
    Swarthmore College, PA, USA.
    Browning, P. K.
    University of Manchester, UK.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Furno, I.
    Ecole Polytechnique Federal de Lausanne, Switzerland .
    Intrator, T. P.
    Los Alamos National Laboratory, NM, USA .
    Microphysics of Cosmic Plasmas: Hierarchies of Plasma Instabilities from MHD to Kinetic2013Inngår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 178, nr 2-4, s. 357-383Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    In this article, we discuss the idea of a hierarchy of instabilities that can rapidly couple the disparate scales of a turbulent plasma system. First, at the largest scale of the system, L, current carrying flux ropes can undergo a kink instability. Second, a kink instability in adjacent flux ropes can rapidly bring together bundles of magnetic flux and drive reconnection, introducing a new scale of the current sheet width, , perhaps several ion inertial lengths (δ i ) across. Finally, intense current sheets driven by reconnection electric fields can destabilize kinetic waves such as ion cyclotron waves as long as the drift speed of the electrons is large compared to the ion thermal speed, v D v i . Instabilities such as these can couple MHD scales to kinetic scales, as small as the proton Larmor radius, ρ i .

  • 16.
    Brown, Michael R
    et al.
    Swarthmore College, Swarthmore, PA 19081, USA.
    Browning, Philippa K
    Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, UK.
    Dieckmann, Mark E
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Furno, Ivo
    EPFL Lausanne, CH-1015 Lausanne, Switzerland.
    Intrator, Tom P
    Los Alamos National Lab, USA.
    Microphysics of Cosmic Plasmas: Hierarchies of Plasma Instabilities from MHD to Kinetic2014Inngår i: Microphysics of cosmic plasmas / [ed] André Balogh, Andrei Bykov, Peter Cargill, Richard DendyThierry and Dudok de WitJohn Raymond, Boston: Springer, 2014, 1, s. 281-307Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    In this article, we discuss the idea of a hierarchy of instabilities that can rapidly couple the disparate scales of a turbulent plasma system. First, at the largest scale of the system, L, current carrying flux ropes can undergo a kink instability. Second, a kink instability in adjacent flux ropes can rapidly bring together bundles of magnetic flux and drive reconnection, introducing a new scale of the current sheet width, , perhaps several ion inertial lengths (δ i ) across. Finally, intense current sheets driven by reconnection electric fields can destabilize kinetic waves such as ion cyclotron waves as long as the drift speed of the electrons is large compared to the ion thermal speed, v D v i . Instabilities such as these can couple MHD scales to kinetic scales, as small as the proton Larmor radius, ρ i .

  • 17.
    Butler, Alexandre
    et al.
    Univ Paris Saclay, France.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. Univ Paris Saclay, France; KTH Royal Inst Technol, Sweden.
    Raadu, Michael A.
    KTH Royal Inst Technol, Sweden.
    Gudmundsson, Jon Tomas
    KTH Royal Inst Technol, Sweden; Univ Iceland, Iceland.
    Minea, Tiberiu
    Univ Paris Saclay, France.
    Lundin, Daniel
    Univ Paris Saclay, France.
    On three different ways to quantify the degree of ionization in sputtering magnetrons2018Inngår i: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 27, nr 10, artikkel-id 105005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantification and control of the fraction of ionization of the sputtered species are crucial in magnetron sputtering, and in particular in high-power impulse magnetron sputtering (HiPIMS), yet proper definitions of the various concepts of ionization are still lacking. In this contribution, we distinguish between three approaches to describe the degree (or fraction) of ionization: the ionized flux fraction F-flux, the ionized density fraction F-density, and the fraction a of the sputtered metal atoms that become ionized in the plasma (sometimes referred to as probability of ionization). By studying a reference HiPIMS discharge with a Ti target, we show how to extract absolute values of these three parameters and how they vary with peak discharge current. Using a simple model, we also identify the physical mechanisms that determine F-flux, F-density, and a as well as how these three concepts of ionization are related. This analysis finally explains why a high ionization probability does not necessarily lead to an equally high ionized flux fraction or ionized density fraction.

  • 18.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Alejo, Aaron
    Centre for Plasma Physics, Queen's University Belfast, Belfast, UK..
    Sarri, Gianluca
    Centre for Plasma Physics, Queen's University Belfast, Belfast, UK..
    Folini, Doris
    Université de Lyon, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon, Lyon, France.
    Walder, Rolf
    Université de Lyon, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon, Lyon, France.
    One-dimensional thermal pressure-driven expansion of a pair cloud into an electron-proton plasma2018Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, nr 5, artikkel-id 064502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently, a filamentation instability was observed when a laser-generated pair cloud interacted with an ambient plasma. The magnetic field it drove was strong enough to magnetize and accelerate the ambient electrons. It is of interest to determine if and how pair cloud-driven instabilities can accelerate ions in the laboratory or in astrophysical plasma. For this purpose, the expansion of a localized pair cloud with the temperature 400 keV into a cooler ambient electron-proton plasma is studied by means of one-dimensional particle-in-cell simulations. The cloud's expansion triggers the formation of electron phase space holes that accelerate some protons to MeV energies. Forthcoming lasers might provide the energy needed to create a cloud that can accelerate protons.

  • 19.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Doria, Domenico
    School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, United Kingdom.
    Ahmed, Hamad
    School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, United Kingdom.
    Romagnani, Lorenzo
    LULI, Ecole Polytechnique, CNRS, CEA, UPMC, Palaiseau, France.
    Sarri, Gianluca
    School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, United Kingdom.
    Folini, Doris
    Université de Lyon, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, Lyon, France.
    Walder, Rolf
    Université de Lyon, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, Lyon, France.
    Bret, Antoine
    ETSI Industriales, Universidad de Castilla-La Mancha, Ciudad Real, Spain.
    Borghesi, Marco
    School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, United Kingdom.
    Expansion of a radial plasma blast shell into an ambient plasma2017Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, nr 9, artikkel-id 094501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expansion of a radial blast shell into an ambient plasma is modeled with a particle-in-cell simulation. The unmagnetized plasma consists of electrons and protons. The formation and evolution of an electrostatic shock is observed, which is trailed by ion-acoustic solitary waves that grow on the beam of the blast shell ions in the post-shock plasma. In spite of the initially radial symmetric outflow, the solitary waves become twisted and entangled and, hence, they break the radial symmetry of the flow. The waves and their interaction with the shocked ambient ions slow down the blast shell protons and bring the post-shock plasma closer to equilibrium.

  • 20.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Folini, Doris
    École Normale Supérieure, Lyon, CRAL, UMR CNRS 5574, Université de Lyon, F-69622 Lyon, France.
    Bret, Antoine
    Universidad de Castilla La Mancha, ETSI Ind, E-13071 Ciudad Real, Spain.
    Walder, Rolf
    École Normale Supérieure, Lyon, CRAL, UMR CNRS 5574, Université de Lyon, F-69622 Lyon, France.
    Simulation studies of temperature anisotropy driven pair-Alfvén and aperiodic instabilities in magnetized pair plasma2019Inngår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, nr 8, artikkel-id 085027Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compare with one-dimensional particle-in-cell simulations the aperiodically growing instabilities driven by a bi-Maxwellian velocity distribution in unmagnetized electron plasma (Weibel instability) and in pair plasma. The simulation box is aligned with the cool direction. The waves in both simulations evolve towards a circularly polarized non-propagating magnetic structure. Its current and magnetic field are aligned and the structure is in a force-free state. We examine how a background magnetic field B 0, which is parallel to the simulation direction, affects the waves in the pair plasma. A weak B 0 cannot inhibit the growth of the aperiodically growing instability but it prevents it from reaching the force-free stable state. The mode collapses and seeds a pair Alfvén waves. An intermediate B 0 couples the thermal anisotropy to the pair Alfvén mode and propagating magnetowaves grow. The phase speed of the pair of Alfvén waves is increased by the thermal anisotropy. Its growth is suppressed when B 0 is set to the value that stabilizes the mirror mode.

  • 21.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Folini, Doris
    École Normale Supérieure, Lyon, CRAL, UMR CNRS 5574, Université de Lyon, F-69007 Lyon, France.
    Walder, Rolf
    École Normale Supérieure, Lyon, CRAL, UMR CNRS 5574, Université de Lyon, F-69007 Lyon, France.
    Romagnani, Lorenzo
    École Polytechnique, CNRS, LULI, F-91128 Palaiseau, France.
    d'Humieres, Emanuel
    Univ Bordeaux, IMB, UMR 5251, F-33405 Talence, France.
    Bret, Antoine
    ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real and Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real, Spain.
    Karlsson, Tomas
    KTH Royal Institute of Technology, School of Electrical Engineering, Space and Plasma Physics, Stockholm, Sweden.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Emergence of MHD structures in a collisionless PIC simulation plasma2017Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, nr 9, artikkel-id 094502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expansion of a dense plasma into a dilute plasma across an initially uniform perpendicular magnetic field is followed with a one-dimensional particle-in-cell simulation over magnetohydrodynamics time scales. The dense plasma expands in the form of a fast rarefaction wave. The accelerated dilute plasma becomes separated from the dense plasma by a tangential discontinuity at its back. A fast magnetosonic shock with the Mach number 1.5 forms at its front. Our simulation demonstrates how wave dispersion widens the shock transition layer into a train of nonlinear fast magnetosonic waves.

  • 22.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Moreno, Quentin
    Universite de Bordeaux, CNRS, CEA, CELIA, Talence, France.
    Doria, Domenico
    Centre for Plasma Physics (CPP), Queen's University Belfast, UK.
    Romagnani, Lorenzo
    Ecole Polytechnique, CNRS, LULI, Palaiseau, France.
    Sarri, Gianluca
    Centre for Plasma Physics (CPP), Queen's University Belfast, UK.
    Folini, Doris
    Ecole Nationale Superieure, Lyon, CRAL, Universite de Lyon, France.
    Walder, Rolf
    Ecole Nationale Superieure, Lyon, CRAL, Universite de Lyon, France.
    Bret, Antoiine
    ETSI Industriales, Universidad de Castilla-La Mancha, Spain.
    d'Humieres, Emmanuel
    Universite de Bordeaux, CNRS, CEA, CELIA, Talence, France.
    Borghesi, Marco
    Centre for Plasma Physics (CPP), Queen's University Belfast, UK.
    Expansion of a radially symmetric blast shell into a uniformly magnetized plasma2018Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, nr 5, artikkel-id 052108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expansion of a thermal pressure-driven radial blast shell into a dilute ambient plasma is examined with two-dimensional PIC simulations. The purpose is to determine if laminar shocks form in a collisionless plasma which resemble their magnetohydrodynamic counterparts. The ambient plasma is composed of electrons with the temperature of 2 keV and cool fully ionized nitrogen ions. It is permeated by a spatially uniform magnetic field. A forward shock forms between the shocked ambient medium and the pristine ambient medium, which changes from an ion acoustic one through a slow magnetosonic one to a fast magnetosonic shock with increasing shock propagation angles relative to the magnetic field. The slow magnetosonic shock that propagates obliquely to the magnetic field changes into a tangential discontinuity for a perpendicular propagation direction, which is in line with the magnetohydrodynamic model. The expulsion of the magnetic field by the expanding blast shell triggers an electron-cyclotron drift instability.

  • 23.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Sarri, G.
    Queens University of Belfast, North Ireland.
    Doria, D.
    Queens University of Belfast, North Ireland.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Borghesi, M.
    Queens University of Belfast, North Ireland.
    Particle-in-cell simulation study of a lower-hybrid shock2016Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 23, nr 6, s. 062111-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasmas expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma. Published by AIP Publishing.

  • 24.
    Dieckmann, Mark E
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Sarri, Gianluca
    Centre for Plasma Physics (CPP), Queen's University Belfast, Belfast, United Kingdom.
    Folini, Doris
    École Normale Supérieure, Université de Lyon, Lyon, France.
    Walder, Rolf
    École Normale Supérieure, Université de Lyon, Lyon, France.
    Borghesi, Marco
    Centre for Plasma Physics (CPP), Queen's University Belfast, Belfast, United Kingdom.
    Cocoon formation by a mildly relativistic pair jet in unmagnetized collisionless electron-proton plasma2018Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, nr 11, artikkel-id 112903Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By modelling the expansion of a cloud of electrons and positrons with the temperature of 400 keV which propagates at the mean speed of 0.9c (c: speed of light) through an initially unmagnetized electron-proton plasma with a particle-in-cell simulation, we find a mechanism that collimates the pair cloud into a jet. A filamentation (beam-Weibel) instability develops. Its magnetic field collimates the positrons and drives an electrostatic shock into the electron-proton plasma. The magnetic field acts as a discontinuity that separates the protons of the shocked ambient plasma, known as the outer cocoon, from the jet's interior region. The outer cocoon expands at the speed of 0.15c along the jet axis and at 0.03c perpendicularly to it. The filamentation instability converts the jet's directed flow energy into magnetic energy in the inner cocoon. The magnetic discontinuity cannot separate the ambient electrons from the jet electrons. Both species rapidly mix and become indistinguishable. The spatial distribution of the positive charge carriers is in agreement with the distributions of the ambient material and the jet material predicted by a hydrodynamic model apart from a dilute positronic outflow that is accelerated by the electromagnetic field at the jet's head.

  • 25.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    The filamentation instability driven by warm electron beams: statistics and electric field generation2009Inngår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 51, nr 12, s. 124042-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The filamentation instability of counterpropagating symmetric beams of electrons is examined with 1D and 2D particle-in-cell simulations, which are oriented orthogonally to the beam velocity vector. The beams are uniform, warm and their relative speed is mildly relativistic. The dynamics of the filaments is examined in 2D and it is confirmed that their characteristic size increases linearly in time. Currents orthogonal to the beam velocity vector are driven through the magnetic and electric fields in the simulation plane. The fields are tied to the filament boundaries and the scale size of the flow aligned and the perpendicular currents are thus equal. It is confirmed that the electrostatic and the magnetic forces are equally important, when the filamentation instability saturates in 1D. Their balance is apparently the saturation mechanism of the filamentation instability for our initial conditions. The electric force is relatively weaker but not negligible in the 2D simulation, where the electron temperature is set higher to reduce the computational cost. The magnetic pressure gradient is the principal source of the electrostatic field, when and after the instability saturates in the 1D simulation and in the 2D simulation.

  • 26.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Alejo, Aaron
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, UK.
    Sarri, Gianluca
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, UK.
    Expansion of a mildly relativistic hot pair cloud into an electron-proton plasma2018Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, nr 6, artikkel-id 062122Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expansion of a charge-neutral cloud of electrons and positrons with the temperature 1 MeV into an unmagnetized ambient plasma is examined with a 2D particle-in-cell simulation. The pair outflow drives solitary waves in the ambient protons. Their bipolar electric fields attract electrons of the outflowing pair cloud and repel positrons. These fields can reflect some of the protons, thereby accelerating them to almost an MeV. Ion acoustic solitary waves are thus an efficient means to couple energy from the pair cloud to protons. The scattering of the electrons and positrons by the electric field slows down their expansion to a nonrelativistic speed. Only a dilute pair outflow reaches the expansion speed expected from the cloud's thermal speed. Its positrons are more energetic than its electrons. In time, an instability grows at the front of the dense slow-moving part of the pair cloud, which magnetizes the plasma. The instability is driven by the interaction of the outflowing positrons with the protons. These results shed light on how magnetic fields are created and ions are accelerated in pair-loaded astrophysical jets and winds.

  • 27.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Bock, Alexander
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Ahmed, Hamad
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, Belfast, UK.
    Doria, Domenico
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, Belfast, UK.
    Sarri, Gianluca
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, Belfast, UK.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Borghesi, Marco
    Centre for Plasma Physics (CPP), Queen's University Belfast, BT7 1NN, Belfast, UK.
    Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation2015Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, nr 7, s. 1-9, artikkel-id 072104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold speed for shock formation. A variation of the collision speed along the initially planar collision boundary, which is comparable to the ion acoustic speed, yields a curvature of the shock that increases with time. The spatially varying Mach number of the shocks results in a variation of the downstream density in the direction along the shock boundary. This variation is eventually equilibrated by the thermal diffusion of ions. The pair of shocks is stable for tens of inverse ion plasma frequencies. The angle between the mean flow velocity vector of the inflowing upstream plasma and the shock's electrostatic field increases steadily during this time. The disalignment of both vectors gives rise to a rotational electron flow, which yields the growth of magnetic field patches that are coherent over tens of electron skin depths.

  • 28.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Bret, Antoine
    ETSI Ind Univ Castilla-La Mancha.
    Electric field generation by the electron beam filamentation instability: filament size effects2010Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 81, nr 1, s. 015502-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The filamentation instability (FI) of counter-propagating beams of electrons is modelled with a particle-in-cell simulation in one spatial dimension and with a high statistical plasma representation. The simulation direction is orthogonal to the beam velocity vector. Both electron beams have initially equal densities, temperatures and moduli of their non-relativistic mean velocities. The FI is electromagnetic in this case. A previous study of a small filament demonstrated that the magnetic pressure gradient force (MPGF) results in a nonlinearly driven electrostatic field. The probably small contribution of the thermal pressure gradient to the force balance implied that the electrostatic field performed undamped oscillations around a background electric field. Here, we consider larger filaments, which reach a stronger electrostatic potential when they saturate. The electron heating is enhanced and electrostatic electron phase space holes form. The competition of several smaller filaments, which grow simultaneously with the large filament, also perturbs the balance between the electrostatic and magnetic fields. The oscillations are damped but the final electric field amplitude is still determined by the MPGF.

  • 29.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Bret, Antoine
    University of Castilla La Mancha, ETSI Ind, Ciudad Real, Spain.
    Simulation study of the formation of a non-relativistic pair shock2017Inngår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 83, s. 1-19, artikkel-id 905830104Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We examine with a particle-in-cell (PIC) simulation the collision of two equally dense clouds of cold pair plasma. The clouds interpenetrate until instabilities set in, which heat up the plasma and trigger the formation of a pair of shocks. The fastest-growing waves at the collision speed $c/5$, where $c$ is the speed of light in vacuum, and low temperature are the electrostatic two-stream mode and the quasi-electrostatic oblique mode. Both waves grow and saturate via the formation of phase space vortices. The strong electric fields of these nonlinear plasma structures provide an efficient means of heating up and compressing the inflowing upstream leptons. The interaction of the hot leptons, which leak back into the upstream region, with the inflowing cool upstream leptons continuously drives electrostatic waves that mediate the shock. These waves heat up the inflowing upstream leptons primarily along the shock normal, which results in an anisotropic velocity distribution in the post-shock region. This distribution gives rise to the Weibel instability. Our simulation shows that even if the shock is mediated by quasi-electrostatic waves, strong magnetowaves will still develop in its downstream region.

  • 30.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Folini, Doris
    Centre de Recherche Astrophysique de Lyon UMR5574, Université de Lyon 1, ENS de Lyon, CNRS, F-69007 Lyon, France.
    Walder, Rolf
    Centre de Recherche Astrophysique de Lyon UMR5574, Université de Lyon 1, ENS de Lyon, CNRS, F-69007 Lyon, France.
    The interplay of the collisionless non-linear thin-shell instability with the ion acoustic instability2017Inngår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 465, nr 4, s. 4240-4248Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The non-linear thin-shell instability (NTSI) may explain some of the turbulent hydrodynamic structures that are observed close to the collision boundary of energetic astrophysical outflows. It develops in non-planar shells that are bounded on either side by a hydrodynamic shock, provided that the amplitude of the seed oscillations is sufficiently large. The hydrodynamic NTSI has a microscopic counterpart in collisionless plasma. A sinusoidal displacement of a thin shell, which is formed by the collision of two clouds of unmagnetized electrons and protons, grows and saturates on time-scales of the order of the inverse proton plasma frequency. Here we increase the wavelength of the seed perturbation by a factor of 4 compared to that in a previous study. Like in the case of the hydrodynamic NTSI, the increase in the wavelength reduces the growth rate of the microscopic NTSI. The prolonged growth time of the microscopic NTSI allows the waves, which are driven by the competing ion acoustic instability, to grow to a large amplitude before the NTSI saturates and they disrupt the latter. The ion acoustic instability thus imposes a limit on the largest wavelength that can be destabilized by the NTSI in collisionless plasma. The limit can be overcome by binary collisions. We bring forward evidence for an overstability of the collisionless NTSI.

  • 31.
    Dieckmann, Mark Eric
    et al.
    Queen’s University Belfast.
    Kourakis, Ioannis
    CPP, Queen's University Belfast, UK.
    Borghesi, Marco
    CPP, Queen's University Belfast, UK.
    Rowlands, George
    Physics Department, Warwick University, UK.
    One-dimensional particle simulation of the filamentation instability: Electrostatic field driven by the magnetic pressure gradient force2009Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, nr 7, s. 074502-1-074502-4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two counterpropagating cool and equally dense electron beams are modeled with particle-in-cell simulations. The electron beam filamentation instability is examined in one spatial dimension, which is an approximation for a quasiplanar filament boundary. It is confirmed that the force on the electrons imposed by the electrostatic field, which develops during the nonlinear stage of the instability, oscillates around a mean value that equals the magnetic pressure gradient force. The forces acting on the electrons due to the electrostatic and the magnetic field have a similar strength. The electrostatic field reduces the confining force close to the stable equilibrium of each filament and increases it farther away, limiting the peak density. The confining time-averaged total potential permits an overlap of current filaments with an opposite flow direction.

  • 32.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Murphy, Gareth
    Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland .
    Meli, Athina
    Center for Astroparticle Physics, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany .
    Drury, Luke O'C
    Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland .
    Particle-in-cell simulation of a mildly relativistic collision of an electron-ion plasma carrying a quasi-parallel magnetic field: Electron acceleration and magnetic field amplification at supernova shocks2010Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 509, nr 1, s. A89-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. Plasma processes close to supernova remnant shocks result in the amplification of magnetic fields and in the acceleration of electrons, injecting them into the diffusive acceleration mechanism.

    Aims. The acceleration of electrons and the magnetic field amplification by the collision of two plasma clouds, each consisting of electrons and ions, at a speed of 0.5c is investigated. A quasi-parallel guiding magnetic field, a cloud density ratio of 10 and a plasma temperature of 25 keV are considered.

    Methods. A relativistic and electromagnetic particle-in-cell simulation models the plasma in two spatial dimensions employing an ion-to-electron mass ratio of 400.

    Results. A quasi-planar shock forms at the front of the dense plasma cloud. It is mediated by a circularly left-hand polarized electromagnetic wave with an electric field component along the guiding magnetic field. Its propagation direction is close to that of the guiding field and orthogonal to the collision boundary. It has a frequency too low to be determined during the simulation time and a wavelength that equals several times the ion inertial length. These properties would be indicative of a dispersive Alfvén wave close to the ion cyclotron resonance frequency of the left-handed mode, known as the ion whistler, provided that the frequency is appropriate. However, it moves with the super-alfvénic plasma collision speed, suggesting that it is an Alfvén precursor or a nonlinear MHD wave such as a Short Large-Amplitude Magnetic Structure (SLAMS). The growth of the magnetic amplitude of this wave to values well in excess of those of the quasi-parallel guiding field and of the filamentation modes results in a quasi-perpendicular shock. We present evidence for the instability of this mode to a four wave interaction. The waves developing upstream of the dense cloud give rise to electron acceleration ahead of the collision boundary. Energy equipartition between the ions and the electrons is established at the shock and the electrons are accelerated to relativistic speeds.

    Conclusions. The magnetic fields in the foreshock of supernova remnant shocks can be amplified substantially and electrons can be injected into the diffusive acceleration, if strongly magnetised plasma subshells are present in the foreshock, with velocities an order of magnitude faster than the main shell.

  • 33.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Murphy, GC
    Dublin Institute for Advanced Studies (DIAS), Dublin 2, Ireland .
    Drury, LOC
    Dublin Institute for Advanced Studies (DIAS), Dublin 2, Ireland .
    Particle-in-cell simulation of a fast nonrelativistic oblique shock: Extreme electron acceleration and magnetic field amplification2010Inngår i: EUROPEAN CONFERENCE ABSTRACTS ECA, European Physical Society , 2010, s. P2.402-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Plasma processes close to astrophysical shocks result in the amplification of magnetic fields and in the acceleration of electrons.We examine with PIC simulations the magnetic field amplification by the collision of two plasma clouds at a speed 0.5c, each consisting of electrons and ions. A quasi-parallel guiding magnetic field, a cloud density ratio of 10 and a plasma temperature of 25 keV are considered.We demonstrate that the magnetic energy density reaches that of the ions and that electrons are accelerated to highly relativistic speeds.

  • 34.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Sarri, Gianluca
    Queen's University of Belfast, UK.
    Borghesi, Marco
    Queen's University of Belfast, UK.
    Magnetic instability in a dilute circular rarefaction wave2012Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 19, nr 12, s. 122102-1-122102-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growth of magnetic fields in the density gradient of a rarefaction wave has been observed in simulations and in laboratory experiments. The thermal anisotropy of the electrons, which gives rise to the magnetic instability, is maintained by the ambipolar electric field. This simple mechanism could be important for the magnetic field amplification in astrophysical jets or in the interstellar medium ahead of supernova remnant shocks. The acceleration of protons and the generation of a magnetic field by the rarefaction wave, which is fed by an expanding circular plasma cloud, is examined here in form of a 2D particle-in-cell simulation. The core of the plasma cloud is modeled by immobile charges, and the mobile protons form a small ring close to the cloud's surface. The number density of mobile protons is thus less than that of the electrons. The protons of the rarefaction wave are accelerated to 1/10 of the electron thermal speed, and the acceleration results in a thermal anisotropy of the electron distribution in the entire plasma cloud. The instability in the rarefaction wave is outrun by a TM wave, which grows in the dense core distribution, and its magnetic field expands into the rarefaction wave. This expansion drives a secondary TE wave.

  • 35.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Sarri, Gianluca
    Queen's University Belfast, UK.
    Doria, Domenico
    Queen's University Belfast, UK.
    Ahmed, Hamad
    Queen's University Belfast, UK.
    Borghesi, Marco
    Queen's University Belfast, UK.
    Evolution of slow electrostatic shock into a plasma shock mediated by electrostatic turbulence2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 073001-1-073001-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The collision of two plasma clouds at a speed that exceeds the ion acoustic speed can result in the formation of shocks. This phenomenon is observed not only in astrophysical scenarios, such as the propagation of supernova remnant (SNR) blast shells into the interstellar medium, but also in laboratory-based laser-plasma experiments. These experiments and supporting simulations are thus seen as an attractive platform for small-scale reproduction and study of astrophysical shocks in the laboratory. We model two plasma clouds, which consist of electrons and ions, with a 2D particle-in-cell simulation. The ion temperatures of both clouds differ by a factor of ten. Both clouds collide at a speed that is realistic for laboratory studies and for SNR shocks in their late evolution phase, like that of RCW86. A magnetic field, which is orthogonal to the simulation plane, has a strength that is comparable to that of SNR shocks. A forward shock forms between the overlap layer of both plasma clouds and the cloud with cooler ions. A large-amplitude ion acoustic wave is observed between the overlap layer and the cloud with hotter ions. It does not steepen into a reverse shock because its speed is below the ion acoustic speed. A gradient of the magnetic field amplitude builds up close to the forward shock as it compresses the magnetic field. This gradient gives rise to an electron drift that is fast enough to trigger an instability. Electrostatic ion acoustic wave turbulence develops ahead of the shock, widens its transition layer, and thermalizes the ions, but the forward shock remains intact.

  • 36.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Sarri, Gianluca
    Queen's University Belfast, UK.
    Doria, Domenico
    Queen's University Belfast, UK.
    Pohl, Martin
    University of Potsdam, Germany .
    Borghesi, Marco
    Queen's University Belfast, UK.
    Modification of the formation of high-Mach number electrostatic shock-like structures by the ion acoustic instability2013Inngår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 20, nr 10, s. 102112-1-102112-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of unmagnetized electrostatic shock-like structures with a high Mach number is examined with one-and two-dimensional particle-in-cell (PIC) simulations. The structures are generated through the collision of two identical plasma clouds, which consist of equally hot electrons and ions with a mass ratio of 250. The Mach number of the collision speed with respect to the initial ion acoustic speed of the plasma is set to 4.6. This high Mach number delays the formation of such structures by tens of inverse ion plasma frequencies. A pair of stable shock-like structures is observed after this time in the 1D simulation, which gradually evolves into electrostatic shocks. The ion acoustic instability, which can develop in the 2D simulation but not in the 1D one, competes with the nonlinear process that gives rise to these structures. The oblique ion acoustic waves fragment their electric field. The transition layer, across which the bulk of the ions change their speed, widens and their speed change is reduced. Double layer-shock hybrid structures develop.

  • 37.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Sarri, Gianluca
    Queen's University Belfast. BT7 1NN, Belfast, United Kingdom.
    Markoff, Sera
    University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
    Borghesi, Marco
    Queen's University Belfast, BT7 1NN, Belfast, United Kingdom.
    Zepf, Matt
    Queen's University Belfast, BT7 1NN, Belfast, United Kingdom.
    PIC simulation study of the interaction between a relativisticallymoving leptonic micro-cloud and ambient electrons.2015Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 577, nr A137, s. 1-10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. The jets of compact accreting objects are composed of electrons and a mixture of positrons and ions. These outflows impinge on the interstellar or intergalactic medium and both plasmas interact via collisionless processes. Filamentation (beam-Weibel) instabilities give rise to the growth of strong electromagnetic fields. These fields thermalize the interpenetrating plasmas.

    Aims. Hitherto, the effects imposed by a spatial non-uniformity on filamentation instabilities have remained unexplored. We examine the interaction between spatially uniform background electrons and a minuscule cloud of electrons and positrons. The cloud size is comparable to that created in recent laboratory experiments and such clouds may exist close to internal and external shocks of leptonic jets. The purpose of our study is to determine the prevalent instabilities, their ability to generate electromagnetic fields and the mechanism, by which the lepton micro-cloud transfers energy to the background plasma.

    Methods. A square micro-cloud of equally dense electrons and positrons impinges in our particle-in-cell (PIC) simulation on a spatially uniform plasma at rest. The latter consists of electrons with a temperature of 1 keV and immobile ions. The initially charge- and current neutral micro-cloud has a temperature of 100 keV and a side length of 2.5 plasma skin depths of the micro-cloud. The side length is given in the reference frame of the background plasma. The mean speed of the micro-cloud corresponds to a relativistic factor of 15, which is relevant for laboratory experiments and for relativistic astrophysical outflows. The spatial distributions of the leptons and of the electromagnetic fields are examined at several times.

    Results. A filamentation instability develops between the magnetic field carried by the micro-cloud and the background electrons. The electromagnetic fields, which grow from noise levels, redistribute the electrons and positrons within the cloud, which boosts the peak magnetic field amplitude. The current density and the moduli of the electromagnetic fields grow aperiodically in time and steadily along the direction that is anti-parallel to the cloud’s velocity vector. The micro-cloud remains conjoined during the simulation. The instability induces an electrostatic wakefield in the background plasma.

    Conclusions. Relativistic clouds of leptons can generate and amplify magnetic fields even if they have a microscopic size, which implies that the underlying processes can be studied in the laboratory. The interaction of the localized magnetic field and high-energy leptons will give rise to synchrotron jitter radiation. The wakefield in the background plasma dissipates the kinetic energy of the lepton cloud. Even the fastest lepton micro-clouds can be slowed down by this collisionless mechanism. Moderately fast charge- and current neutralized lepton micro–clouds will deposit their energy close to relativistic shocks and hence they do not constitute an energy loss mechanism for the shock.

  • 38.
    Dieckmann, Mark Eric
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Sarri, Gianluca
    Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
    Romagnani, Lorenzo
    Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
    Kourakis, Ioannis
    Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
    Borghesi, Marco
    Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
    Simulation of a collisionless planar electrostatic shock in a proton–electron plasma with a strong initial thermal pressure change2010Inngår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 52, nr 2, s. 025001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The localized deposition of the energy of a laser pulse, as it ablates a solid target, introduces high thermal pressure gradients in the plasma. The thermal expansion of this laser-heated plasma into the ambient medium (ionized residual gas) triggers the formation of non-linear structures in the collisionless plasma. Here an electron–proton plasma is modelled with a particle-in-cell simulation to reproduce aspects of this plasma expansion. A jump is introduced in the thermal pressure of the plasma, across which the otherwise spatially uniform temperature and density change by a factor of 100. The electrons from the hot plasma expand into the cold one and the charge imbalance drags a beam of cold electrons into the hot plasma. This double layer reduces the electron temperature gradient. The presence of the low-pressure plasma modifies the proton dynamics compared with the plasma expansion into a vacuum. The jump in the thermal pressure develops into a primary shock. The fast protons, which move from the hot into the cold plasma in the form of a beam, give rise to the formation of phase space holes in the electron and proton distributions. The proton phase space holes develop into a secondary shock that thermalizes the beam.

  • 39.
    Ekeroth, Sebastian
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nanomaterials are important tools for enabling technological progress as they can provide dramatically different properties as compared to the bulk counterparts. The field of nanoparticles is one of the most investigated within nanomaterials, thanks to the existing, relatively simple, means of manufacturing. In this thesis, high-power pulsed hollow cathode sputtering is used to nucleate and grow magnetic nanoparticles in a plasma. This sputtering technique provides a high degree of ionization of the sputtered material, which has previously been shown to aid in the growth of the nanoparticles. The magnetic properties of the particles are utilized and makes it possible for the grown particles to act as building blocks for self-assembly into more sophisticated nano structures, particularly when an external magnetic field is applied. These structures created are termed “nanowires” or “nanotrusses”, depending on the level of branching and inter-linking that occurs.

    Several different elements have been investigated in this thesis. In a novel approach, it is shown how nanoparticles with more advanced structures, and containing material from two hollow cathodes, can be fabricated using high-power pulses. The dual-element particles are achieved by using two distinct and individual elemental cathodes, and a pulse process that allows tuning of individual pulses separately to them. Nanoparticles grown and investigated are Fe, Ni, Pt, Fe-Ni and Ni-Pt. Alternatively, the addition of oxygen to the process allows the formation of oxide or hybrid metal oxide – metal particles. For all nanoparticles containing several elements, it is demonstrated that the stoichiometry can be easily varied, either by the amount of reactive gas let into the process or by tuning the amount of sputtered material through adjusting the electric power supplied to the different cathodes.

    One aim of the presented work is to find a suitable material for the use as a catalyst in the production of H2 gas through the process of water splitting. H2 is a good candidate to replace fossil fuels as an energy carrier. However, rare elements (such as Ir or Pt) needs to be used as the catalyst, otherwise a high overpotential is required for the splitting to occur, leading to a low efficiency. This work demonstrates a possible route to avoid this, by using nanomaterials to increase the surface-to-volume ratio, as well as optimizing the elemental ratio between different materials to lower the amount of noble elements required. 

    Delarbeid
    1. Catalytic Nanotruss Structures Realized by Magnetic Self-Assembly in Pulsed Plasma
    Åpne denne publikasjonen i ny fane eller vindu >>Catalytic Nanotruss Structures Realized by Magnetic Self-Assembly in Pulsed Plasma
    Vise andre…
    2018 (engelsk)Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 5, s. 3132-3137Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 mu m thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H-2 gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm(2).

    sted, utgiver, år, opplag, sider
    American Chemical Society (ACS), 2018
    Emneord
    Nanotrusses; nanowires; nanoparticles; iron; electrocatalysis; pulsed sputtering
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-148107 (URN)10.1021/acs.nanolett.8b00718 (DOI)000432093200055 ()29624405 (PubMedID)
    Forskningsfinansiär
    Knut and Alice Wallenberg Foundation, KAW 14.0276
    Tilgjengelig fra: 2018-05-30 Laget: 2018-05-30 Sist oppdatert: 2019-11-11
    2. Growth of semi-coherent Ni and NiO dual-phase nanoparticles using hollow cathode sputtering
    Åpne denne publikasjonen i ny fane eller vindu >>Growth of semi-coherent Ni and NiO dual-phase nanoparticles using hollow cathode sputtering
    Vise andre…
    2019 (engelsk)Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 21, nr 2, artikkel-id 37Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Anisotropic heterogenous Ni/NiO nanoparticles with controlled compositions are grown using a high-power pulsed hollow cathode process. These novel particles can be tuned to consist of single-phase Ni via two-phase Ni/NiO to fully oxidized NiO, with a size range of 5-25 nm for individual crystals. A novelty of this approach is the ability to assemble multiple particles of Ni and NiO into a single complex structure, increasing the Ni-NiO interface density. This type of particle growth is not seen before and is explained to be due to the fact that the process operates in a single-step approach, where both Ni and O can arrive at the formed nanoparticle nuclei and aid in the continuous particle growth. The finished particle will then be a consequence of the initially formed crystal, as well as the arrival rate ratio of the two species. These particles hold great potential for applications in fields, such as electro- and photocatalysis, where the ability to control the level of oxidation and/or interface density is of great importance.

    sted, utgiver, år, opplag, sider
    SPRINGER, 2019
    Emneord
    Ni; NiO; Anisotropic; Nanoparticles; Hollow cathode; Nanoparticle assembly
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-154838 (URN)10.1007/s11051-019-4479-4 (DOI)000458657800001 ()
    Merknad

    Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 2014.0276]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Tokyo Metropolitan University; Linkoping University

    Tilgjengelig fra: 2019-03-07 Laget: 2019-03-07 Sist oppdatert: 2019-11-11
    3. Impact of nanoparticle magnetization on the 3D formation of dual-phase Ni/NiO nanoparticle-based nanotrusses
    Åpne denne publikasjonen i ny fane eller vindu >>Impact of nanoparticle magnetization on the 3D formation of dual-phase Ni/NiO nanoparticle-based nanotrusses
    Vise andre…
    2019 (engelsk)Inngår i: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 21, nr 11, artikkel-id 21:228Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Magnetic nanoparticles with average size 30 nm were utilized to build three-dimensional framework structures—nanotrusses. In dual-phase Ni/NiO nanoparticles, there is a strong correlation between the amount of magnetic Ni and the final size and shape of the nanotruss. As it decreases, the length of the individual nanowires within the trusses also decreases, caused by a higher degree of branching of the wires. The position and orientation of the non-magnetic material within the truss structure was also investigated for the different phase compositions. For lower concentrations of NiO phase, the electrically conducting Ni-wire framework is maintained through the preferential bonding between the Ni crystals. For larger concentrations of NiO phase, the Ni-wire framework is interrupted by the NiO. The ability to use nanoparticles that are only partly oxidized in the growth of nanotruss structures is of great importance. It opens the possibility for using not only magnetic metals such as pure Ni, Fe, and Co, but also to use dual-phase nanoparticles that can strongly increase the efficiency of e.g. catalytic electrodes and fuel cells.

    sted, utgiver, år, opplag, sider
    Springer-Verlag New York, 2019
    Emneord
    Ni, NiO, Nanotruss, Nanoparticle, Magnetic assembly
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-161747 (URN)10.1007/s11051-019-4661-8 (DOI)000494039300001 ()
    Merknad

    Funding agencies

    Tilgjengelig fra: 2019-11-08 Laget: 2019-11-08 Sist oppdatert: 2019-11-19bibliografisk kontrollert
  • 40.
    Forslund, Ola Kenji
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Manipulation of positron plasma using the AEgIS system at CERN2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    AEgIS is an experiment at CERN where the goal is to directly measure the gravitational force on antimatter by producing antihydrogen. The antihydrogen will be produced by a charge exchange reaction using laser excited positronium and cold antiprotons. Having a well-characterized positron plasma with at least 108 positrons and knowing how it can be controlled is essential for the positronium production. This thesis is based on the goals of AEgIS experiment and describes the positron plasma manipulations being used in AEgIS in order to achieve the required plasma properties for the experiment. The positron system is made up by a source, a Surko trap and a Penning-Malmberg trap. This system was first optimized to increase the number of positrons. The plasma was then moved to the main traps of the experiment where it was systematically characterized in terms of lifetime, cooling efficiency and compression. Positron plasma compression in time, trapping and cooling was tested for the first time in AEgIS using a buncher and Penning-Malmberg traps respectively. In this thesis, it is shown that a compression of more than 50 % in time of the positron cloud using a buncher can be achieved. It is also shown that trapping and cooling with an efficiency of nearly 100 % in the main traps using a “V” shaped potential trap was successful. On top of that, the lifetime inside this “V” shaped potential trap was observed to be longer than 30 minutes.

  • 41.
    Gradov, O. M.
    et al.
    Russian Acad Sci, Russia.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Basic properties of nonlinear surface charge waves at a plasma boundary2018Inngår i: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 42-43, s. 3083-3085Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nonlinear properties of surface charges are here analyzed under ideal conditions. We thus deduce a new single equation from the wellknown equations which govern the cold electron plasma motion. Simple formulas that describe the propagation of surface charge perturbations along the plasma boundary are also found. (C) 2018 Elsevier B.V. All rights reserved.

  • 42.
    Gudmundsson, J. T.
    et al.
    KTH Royal Institute Technology, Sweden; University of Iceland, Iceland; University of Paris Saclay, France.
    Lundin, D.
    University of Paris Saclay, France.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Huo, Chunqing
    KTH Royal Institute Technology, Sweden.
    Minea, T. M.
    University of Paris Saclay, France.
    An ionization region model of the reactive Ar/O-2 high power impulse magnetron sputtering discharge2016Inngår i: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 25, nr 6, s. 065004-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O-2 high power impulse magnetron sputtering (HiPIMS) discharge with a titanium target. It is then applied to study the temporal behavior of the discharge plasma parameters such as electron density, the neutral and ion composition, the ionization fraction of the sputtered vapor, the oxygen dissociation fraction, and the composition of the discharge current. We study and compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we explore the current increase and find that when the discharge is operated in the metal mode Ar+ and Ti+ -ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+ -ions contribute most significantly to the discharge current and the contribution of O+ -ions, Ti+ -ions, and secondary electron emission is much smaller. Furthermore, we find that recycling of atoms coming from the target, that are subsequently ionized, is required for the current generation in both modes of operation. From the R-IRM results it is found that in the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates. We also show that working gas recycling can lead to very high discharge currents but never to a runaway. It is concluded that the dominating type of recycling determines the discharge current waveform.

  • 43.
    Huo, Chunqing
    et al.
    KTH Royal Institute Technology, Sweden; Hainan University, Peoples R China.
    Lundin, D.
    University of Paris Saclay, France.
    Gudmundsson, J. T.
    KTH Royal Institute Technology, Sweden; University of Paris Saclay, France; University of Iceland, Iceland.
    Raadu, M. A.
    KTH Royal Institute Technology, Sweden.
    Bradley, J. W.
    University of Liverpool, England.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden.
    Particle-balance models for pulsed sputtering magnetrons2017Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, nr 35, artikkel-id 354003Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The time-dependent plasma discharge ionization region model (IRM) has been under continuous development during the past decade and used in several studies of the ionization region of high-power impulse magnetron sputtering (HiPIMS) discharges. In the present work, a complete description of the most recent version of the IRM is given, which includes improvements, such as allowing for returning of the working gas atoms from the target, a separate treatment of hot secondary electrons, addition of doubly charged metal ions, etc. To show the general applicability of the IRM, two different HiPIMS discharges are investigated. The first set concerns 400 mu s long discharge pulses applied to an Al target in an Ar atmosphere at 1.8 Pa. The second set focuses on 100 mu s long discharge pulses applied to a Ti target in an Ar atmosphere at 0.54 Pa, and explores the effects of varying the magnetic field strength. The model results show that Al2+-ions contribute negligibly to the production of secondary electrons, while Ti2+-ions effectively contribute to the production of secondary electrons. Similarly, the model results show that for an argon discharge with Al target the contribution of Al+-ions to the discharge current at the target surface is over 90% at 800 V. However, at 400 V the Al+-ions and Ar+-ions contribute roughly equally to the discharge current in the initial peak, while in the plateau region Ar+-ions contribute to roughly 2/3 of the current. For high currents the discharge with Al target develops almost pure self-sputter recycling, while the discharge with Ti target exhibits close to a 50/50 combination of self-sputter recycling and working gas-recycling. For a Ti target, a self-sputter yield significantly below unity makes working gas-recycling necessary at high currents. For the discharge with Ti target, a decrease in the B-field strength, resulted in a corresponding stepwise increase in the discharge resistivity.

  • 44.
    Karimov, A. R.
    et al.
    National Research Nucl University of MEPhI, Russia; Russian Academic Science, Russia.
    Shatokhin, V. L.
    National Research Nucl University of MEPhI, Russia.
    Yu, M. Y.
    Institute Fus Theory and Simulat, Peoples R China; Ruhr University, Germany.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten. Umeå University, Sweden.
    The processes of nonequilibrium exchange in rotating plasma flows2016Inngår i: II CONFERENCE ON PLASMA and LASER RESEARCH AND TECHNOLOGIES, IOP PUBLISHING LTD , 2016, Vol. 747, artikkel-id UNSP 012077Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The mechanisms of energy/momentum exchange in rotating and compressing plasma flows have been discussed. It has been shown that such flows are capable of transforming the energy of different degrees of freedom into the energy of one degree owing to the interaction of the coupled nonlinear radial, axial and azimuthal electron-ion oscillations. These processes may lead to the additional acceleration of the flow in azimuthal or axial direction so they might be instrumental for the creation of space thrusters employing pulse transformations for propulsion.

  • 45.
    Karimov, A. R.
    et al.
    Russian Academic Science, Russia; National Research Nucl University of MEPhI, Russia.
    Yu, M. Y.
    Zhejiang University, Peoples R China; Ruhr University of Bochum, Germany.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    A new class of exact solutions for Vlasov-Poisson plasmas2016Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 91, nr 11, s. 114002-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new class of exact solutions of the Vlasov-Poisson equations based on the Jeans theorem is considered. The self-consistent solutions for the evolution of the system from given initial particle distributions make use of particular invariants of particle motion with predetermined spatial structure. The relation between the time-dependent coefficients of the latter and the macroscopic plasma quantities, or moments of the distribution function, are obtained. As an illustration, the evolution of an expanding plasma with oscillations of the electron and ion expansion fronts is presented.

  • 46.
    Karimov, A. R.
    et al.
    Russian Academic Science, Russia; National Research Nucl University of MEPhI, Russia.
    Yu, M. Y.
    Zhejiang University, Peoples R China; Ruhr University of Bochum, Germany.
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Properties and evolution of anisotropic structures in collisionless plasmas2016Inngår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 82, artikkel-id 905820502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new class of exact electrostatic solutions of the Vlasov-Maxwell equations based on the Jeanss theorem is proposed for studying the evolution and properties of two-dimensional anisotropic plasmas that are far from thermodynamic equilibrium. In particular, the free expansion of a slab of electron-ion plasma into vacuum is investigated.

  • 47.
    Keraudy, Julien
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. Oerlikon Surface Solut AG, Liechtenstein.
    Viloan, Rommel Paulo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Raadu, Michael A.
    KTH Royal Inst Technol, Sweden.
    Brenning, Nils
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten. KTH Royal Inst Technol, Sweden; Univ Paris Saclay, France.
    Lundin, Daniel
    Univ Paris Saclay, France.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska fakulteten.
    Bipolar HiPIMS for tailoring ion energies in thin film deposition2019Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 359, s. 433-437Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of a positive pulse following a high-power impulse magnetron sputtering (HiPIMS) pulse are studied using energy-resolved mass spectrometry. This includes exploring the influence of a 200 mu s long positive voltage pulse (U-rev = 10-150 V) following a typical HiPIMS pulse on the ion-energy distribution function (IEDF) of the various ions. We find that a portion of the Ti+ flux is affected and gains an energy which corresponds to the acceleration over the full potential U-rev. The Ar+ IEDF on the other hand illustrates that a large fraction of the accelerated Ar+, gain energies corresponding to only a portion of U-rev. The Ti+ IEDFs are consistent with the assumption that practically all the TO-, that are accelerated during the reverse pulse, originates from a region adjacent to the target, in which the potential is uniformly increased with the applied potential U-rev while much of the Ar+ originates from a region further away from the target over which the potential drops from U-rev to a lower potential consistent with the plasma potential achieved without the application of U-rev. The deposition rate is only slightly affected and decreases with U-rev, reaching 90% at U-rev = 150 V. Both the Ti IEDF and the small deposition rate change indicate that the potential increase in the region close to the target is uniform and essentially free of electric fields, with the consequence that the motion of ions inside the region is not much influenced by the application of U-rev. In this situation, Ti will flow towards the outer boundary of the target adjacent region, with the momentum gained during the HiPIMS discharge pulse, independently of whether the positive pulse is applied or not. The metal ions that cross the boundary in the direction towards the substrate, and do this during the positive pulse, all gain an energy corresponding to the full positive applied potential U-rev.

  • 48.
    Lai, Chung-Chuan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik.
    Growth and Phase Stability of Titanium Aluminum Nitride Deposited by High Power Impulse Magnetron Sputtering2011Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    In this work, we investigate the relation between the diffusion behavior of Ti1-xAlxN at elevated temperatures and the microstructure. Thinfilm samples are synthesized by reactive co-sputtering with two cathodes. One cathode equipped with Ti target is connected to a highpower impulse magnetron sputtering (HiPIMS) power supply, and the other cathode equipped with Al target is operated with a directcurrent power source. The spinodal decomposition of cubic metastable Ti1-xAlxN controlled by thermally activated diffusion is observe fordiffusion behavior. Various HiPIMS pulsing frequencies are used to achieve different microstructure, while altered power applied to Altarget is used to change the Al content in films. In the phase composition analysis achieved by GI-XRD, the right-shift of (111) film peakalong with increasing Al-power is observed. A saturation of the right-shift and h-AlN peaks are also observed at certain Al-power. Thechemical composition determined by ERDA shows trends of reducing Al solubility limit in metastable phase and O contamination upondecreasing the pulsing frequency. More N deficiency is found in samples deposited with higher frequency. In the 500 Hz and 250 Hzsamples deposited into similar composition and thickness, no apparent difference of the microstructure is observed from the SEM crosssectionalimages. From HT-XRD, we observe higher intensity of TiO2 and h-AlN peaks in 500 Hz sample at elevated temperature ascompared with 250 Hz one. From the reduction of O contamination, denser Ti1-xAlxN films are able to be deposited with lower HiPIMSpulsing frequency. In addition, the higher intensity observed in HT-XRD patterns indicates that the 500 Hz sample is more open todiffusion and therefore allows the new formed phases to grow in larger grains.

  • 49.
    Lazar, Marian
    et al.
    Leuven University, Belgium.
    Dieckmann, Mark Eric
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Resonant Weibel instability in counterstreaming plasmas with temperature anisotropies2010Inngår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 76, nr 1, s. 49-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Weibel instability, driven by a plasma temperature anisotropy, is non-resonant with plasma particles: it is purely growing in time, and does not oscillate. The effect of a counterstreaming plasma is examined. In a counterstreaming plasma with an excess of transverse temperature, the Weibel instability arises along the streaming direction. Here it is proved that for large wave-numbers the instability becomes resonant with a finite real (oscillation) frequency, ωr ≠ 0. When the plasma flows faster, with a bulk velocity larger than the parallel thermal velocity, the instability becomes dominantly resonant. This new feature of the Weibel instability can be relevant for astrophysical sources of non-thermal emissions and the stability of counterflowing plasma experiments.

  • 50.
    Lundin, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Plasma properties in high power impulse magnetron sputtering2008Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The work presented in this thesis involves experimental and theoretical studies related to plasma properties in high power impulse magnetron sputtering (HiPIMS), and more specifically plasma transport. HiPIMS is an ionized PVD method based on conventional direct current magnetron sputtering (dcMS). In dcMS very little of the sputtered material is ionized since the plasma power density is not high enough. This is not the case for HiPIMS, where a substantial part is ionized, and thus presents many new opportunities for thin film growth. Understanding the dynamics of the charged species in the HiPIMS discharge is therefore of essential value when producing high-quality thin film coatings.

    In the first part of the work a new type of anomalous electron transport was found. Investigations of the transport resulted in the discovery that this phenomenon could quantitatively be described as being related and mediated by highly nonlinear waves, likely due to the modified two-stream instability (MTSI), resulting in electric field oscillations in the MHz-range (the so-called lower hybrid frequency). Measurements in the plasma confirmed these oscillations as well as trends predicted by the theory of these types of waves. The degree of anomalous transport in the plasma could also be determined by measuring the current density ratio between the azimuthal current density (of which the Hall current density is one contribution) and the discharge current density, Jφ / JD. The results provided important insights into understanding the mechanism behind the anomalous transport.

    It was furthermore found that the current ratio Jφ / JD is inversely proportional to the transverse resistivity, eta_perpendicular , which governs how well momentum is transferred from the electrons to the ions in the plasma. By looking at the forces involved in the charged particle transport it was expected that the azimuthally rotating electrons would exert a volume force on the ions tangentially outwards from the circular race track region. The effect of having an anomalous transport would therefore be a large fraction of highly energetic ions being transported sideways and lost to the walls. In a series of experiments, deposition rates as well as incoming ion energy distributions were measured directly at the side of the magnetron. It was found that a substantial fraction of sputtered material is transported radially away from the cathode and lost to the walls in HiPIMS as well as dcMS, but more so for HiPIMS giving one possible explanation to why the deposition rate for substrates placed in front of the target is lower for HiPIMS compared to dcMS. Furthermore, the recorded, incoming ion energy distributions confirmed theoretical estimations on this type of transport regarding energy and direction.

    Delarbeid
    1. Anomalous electron transport in high power impulse magnetron sputtering
    Åpne denne publikasjonen i ny fane eller vindu >>Anomalous electron transport in high power impulse magnetron sputtering
    Vise andre…
    2008 (engelsk)Inngår i: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, nr 2, s. 025007-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason for these oscillations to occur is charge perturbation—or so-called modified two-stream instabilities (MTSIs). It is known that MTSIs give rise to acceleration of the charged plasma species and can give a net transport of electrons across the magnetic field lines. Measurements of these oscillations confirm trends, specifically of the frequency dependence on ion mass and magnetic field strength as expected from the theory of MTSI waves. These results help to explain the previously reported anomalous fast electron transport in HIPIMS discharges, where classical theory of diffusion using collisions to transport electrons has failed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13208 (URN)10.1088/0963-0252/17/2/025007 (DOI)
    Merknad
    Original Publication: Daniel Lundin, Ulf Helmersson, Scott Kirkpatrick, Suzanne Rohde and Nils Brenning, Anomalous electron transport in high power impulse magnetron sputtering, 2008, Plasma Sources Science and Technology, (17), 2, 025007. http://dx.doi.org/10.1088/0963-0252/17/2/025007 Copyright: IOP Publishing http://www.iop.org/ Tilgjengelig fra: 2009-02-22 Laget: 2009-02-17 Sist oppdatert: 2013-10-30bibliografisk kontrollert
    2. Cross-field ion transport during high power impulse magnetron sputtering
    Åpne denne publikasjonen i ny fane eller vindu >>Cross-field ion transport during high power impulse magnetron sputtering
    Vise andre…
    2008 (engelsk)Inngår i: Plasma Sources Science and Technology, ISSN 0963-0252, Vol. 17, nr 035021Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode (perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-13209 (URN)10.1088/0963-0252/17/3/035021 (DOI)
    Merknad
    Original Publication: Daniel Lundin, Petter Larsson, Erik Wallin, Martina Lattemann, Nils Brenning and Ulf Helmersson, Cross-field ion transport during high power impulse magnetron sputtering, 2008, Plasma Sources Science and Technology, (17), 035021. http://dx.doi.org/10.1088/0963-0252/17/3/035021 Copyright: Iop Publishing http://www.iop.org/ Tilgjengelig fra: 2009-02-26 Laget: 2009-02-26 Sist oppdatert: 2013-10-30bibliografisk kontrollert
12 1 - 50 of 81
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf