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  • 1. Gonoskov, A.
    et al.
    Bastrakov, S.
    Efimenko, E.
    Ilderton, A.
    Marklund, M.
    Meyerov, I.
    Muraviev, A.
    Sergeev, A.
    Surmin, I.
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Extended particle-in-cell schemes for physics in ultrastrong laser fields: Review and developments2015In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 92, no 2, article id 023305Article in journal (Refereed)
    Abstract [en]

    We review common extensions of particle-in-cell (PIC) schemes which account for strong field phenomena in laser-plasma interactions. After describing the physical processes of interest and their numerical implementation, we provide solutions for several associated methodological and algorithmic problems. We propose a modified event generator that precisely models the entire spectrum of incoherent particle emission without any low-energy cutoff, and which imposes close to the weakest possible demands on the numerical time step. Based on this, we also develop an adaptive event generator that subdivides the time step for locally resolving QED events, allowing for efficient simulation of cascades. Further, we present a unified technical interface for including the processes of interest in different PIC implementations. Two PIC codes which support this interface, PICADOR and ELMIS, are also briefly reviewed.

  • 2. Gonoskov, A.
    et al.
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Polovinkin, A.
    Meyerov, I.
    Employing machine learning for theory validation and identification of experimental conditions in laserplasma physics2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 7043Article in journal (Refereed)
    Abstract [en]

    The validation of a theory is commonly based on appealing to clearly distinguishable and describable features in properly reduced experimental data, while the use of ab-initio simulation for interpreting experimental data typically requires complete knowledge about initial conditions and parameters. We here apply the methodology of using machine learning for overcoming these natural limitations. We outline some basic universal ideas and show how we can use them to resolve long-standing theoretical and experimental difficulties in the problem of high-intensity laser-plasma interactions. In particular we show how an artificial neural network can "read" features imprinted in laser-plasma harmonic spectra that are currently analysed with spectral interferometry.

  • 3.
    Hansson, Tobias
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Marklund, Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Scalar Wigner theory for polarized light in nonlinear Kerr media2013In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 30, no 6, p. 1765-1769Article in journal (Refereed)
    Abstract [en]

    A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability. (C) 2013 Optical Society of America

  • 4. Harvey, C. N.
    et al.
    Gonoskov, A.
    Marklund, M.
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Narrowing of the emission angle in high-intensity Compton scattering2016In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 93, no 2, article id 022112Article in journal (Refereed)
    Abstract [en]

    We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities (a0∼200) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.

  • 5. Harvey, Christopher
    et al.
    Marklund, Mattias
    Wallin, Erik
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-energy gamma-ray beams from nonlinear Thomson and Compton cattering in the ultra-intense regime2015In: Relativistic plasma waves and particle beams as coherent and incoherent radiation sources / [ed] Jaroszynski, DA, 2015, Vol. 9509, article id 950908Conference paper (Refereed)
    Abstract [en]

    We consider the Thomson and Compton scattering of high-energy electrons n an intense laser pulse. Our simulations show that energy losses due o radiation reaction cause the emitted radiation to be spread over a roader angular range than the case without these losses included. We xplain this in terms of the effect of these energy losses on the article dynamics. Finally, at ultra-high intensities, i.e. fields with dimensionless parameter a(0)similar to 200, the energy of the ission pectrum is significantly reduced by radiation reaction and also the lassical and QED results begin to differ. This is found to be due to he classical theory overestimating the energy loss of the electrons. uch findings are relevant to radiation source development involving e ext generation of high-intensity laser facilities.

  • 6.
    Wallin, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Applied Physics, Chalmers University of Technology, SE–412 96 Göteborg, Sweden.
    Gonoskov, Arkady
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden; Nizhny Novgorod, Russia .
    Marklund, Mattias
    Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
    Effects of high energy photon emissions in laser generated ultra-relativistic plasmas: Real-time synchrotron simulations2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 3, article id 033117Article in journal (Refereed)
    Abstract [en]

    We model the emission of high energy photons due to relativistic charged particle motion in intense laser-plasma interactions. This is done within a particle-in-cell code, for which high frequency radiation normally cannot be resolved due to finite time steps and grid size. A simple expression for the synchrotron radiation spectra is used together with a Monte-Carlo method for the emittance. We extend previous work by allowing for arbitrary fields, considering the particles to be in instantaneous circular motion due to an effective magnetic field. Furthermore, we implement noise reduction techniques and present validity estimates of the method. Finally, we perform a rigorous comparison to the mechanism of radiation reaction, and find the emitted energy to be in excellent agreement with the losses calculated using radiation reaction. (C) 2015 AIP Publishing LLC.

  • 7.
    Wallin, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zamanian, Jens
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Three-wave interaction and Manley-Rowe relations in quantum hydrodynamics2014In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 80, p. 643-652Article in journal (Refereed)
    Abstract [en]

    The theory for nonlinear three-wave interaction in magnetized plasmas is reconsidered using quantum hydrodynamics. The general coupling coefficients are calculated for the generalized Bohm de Broglie term. It is found that the Manley-Rowe relations are fulfilled only if the form of the particle dispersive term coincides with the standard expression. The implications of our results are discussed.

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