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26Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2019
STOCHASTIC ELECTRON HEATING IN COMBINED LASER AND
PLASMA FIELDS
S.G. Bochkarev1,5, D.A. Gozhev1, E. d' Humieres2, V.T. Tikhonchuk23, Ph. Korneev4,
V.Yu. Bychenkov1,5
1P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia,
e-mail: bochkarevsg@lebedev.ru 2CELIA, University of Bordeaux, CNRS, CEA, Talence, France, e-mail: vladimir.tikhontchouk@u-bordeaux.fr 3ELI-Beamlines, Institute of Physics, Czech Academy of Sciences, Dolni Brezany, Czech Republic 4National Research Nuclear University "MEPhl" (Moscow Engineering Physics Institute), Moscow,
Russia, e-mail: korneev@theor.mephi.ru 5Center for Fundamental and Applied Research, VNIIA, ROSATOM, Moscow, Russia
A typical situation in experiments on the interaction of short relativistically strong laser pulses with plasmas is a presence of suprathermal particles in electron and ion distributions as a result of effective energy transfer to high-energy particles. However, mechanisms of high-energy particles generation are not completely understood up to the present day. Electron acceleration and heating to high energies are often attributed to stochastic instabilities developing in complex laser fields in the near vacuum (underdense) plasmas. In this report a few schemes of stochastic heating are discussed. The first scheme exploits the scenario where a high laser contrast, as well as a sharp plasma-vacuum interface provide unique conditions for the stochasticity occurrence in complex fields which are a combination of incident and reflected pulses, and some time quasistationary fields, induced near the plasma-vacuum interface [1]. Recent experiments motivated by the goal of boosting of the maximum energy of accelerated ions and exploited an innovative scheme of target irradiation by a few beams demonstrate formation of a hot component in the spectrum of electrons with a temperature much higher than their corresponding ponderomotive energy. When the target surface was irradiated with several beams the suprathermal electrons were produced and ions were accelerated to the higher energies than in the case of a single beam with the same total energy [2]. In this work we demonstrate that stochastic heating process may contribute to production of suprathermal electrons. Another scheme of the stochasticity occurrence is electron acceleration and heating in nanostructured target consisting of numerous nanowires along the normal to the planar target surface. The nanostructured plasma is the unique media which is favorable for generation of high energy electrons, ultrabright X rays, accelerated ions and thermonuclear neutrons [3,4].
We report on enhanced electron heating for these schemes due to synergetic effects in complex laser and plasma fields. Our test particle simulations reveal a generation of suprathermal particles through contributions of stochastic electron trajectories. The spectra of accelerated electrons are well described by an exponential distribution with a characteristic temperature that is several times greater than the ponderomotive energy. These examples demonstrate an importance of stochastic effects for laser plasma heating. The work was partially supported by Russian Science Foundation (Grant No. 17-12-01283).
References
[1] Y. Sentoku et al. 2002 Appl. Phys. B 74 207.
[2] A. Yogo et al. 2017 Sci. Rep. 7, 42451; N. Iwata et al. 2017 Phys. Plasmas 24 073111.
[3] C. Bargsten et al. 2017 Sci.Adv. 3 e1601558.
[4] A. Curtis et al. 2018 Nature Comm. 9, 1077.
