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Title: Magnetic field generation during intense laser channelling in underdense plasma

Abstract

Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.

Authors:
; ; ; ;  [1]; ; ; ;  [2]; ; ;  [3]; ;  [4]; ; ;  [5]
  1. School of Mathematics and Physics, The Queen's University of Belfast, University Road, Belfast BT7 1NN (United Kingdom)
  2. GoLP/IPFN, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon (Portugal)
  3. Graduate School of Engineering Osaka University. Suita, Osaka 5650871 (Japan)
  4. STFC Rutherford Appleton Laboratory, Didcot, Oxon OX1 0Qx (United Kingdom)
  5. Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BZ (United Kingdom)
Publication Date:
OSTI Identifier:
22598926
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 23; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CHANNELING; DEUTERIUM; ELECTRON BEAMS; ELECTRONS; INERTIAL CONFINEMENT; LASERS; MAGNETIC FIELDS; PLASMA; PROTONS; PULSES; RELATIVISTIC RANGE; THERMONUCLEAR IGNITION

Citation Formats

Smyth, A. G., Sarri, G., Doria, D., Kar, S., Borghesi, M., Vranic, M., Guillaume, E., Silva, L. O., Vieira, J., Amano, Y., Habara, H., Tanaka, K. A., Heathcote, R., Norreys, P. A., Hicks, G., Najmudin, Z., and Nakamura, H. Magnetic field generation during intense laser channelling in underdense plasma. United States: N. p., 2016. Web. doi:10.1063/1.4953547.
Smyth, A. G., Sarri, G., Doria, D., Kar, S., Borghesi, M., Vranic, M., Guillaume, E., Silva, L. O., Vieira, J., Amano, Y., Habara, H., Tanaka, K. A., Heathcote, R., Norreys, P. A., Hicks, G., Najmudin, Z., & Nakamura, H. Magnetic field generation during intense laser channelling in underdense plasma. United States. doi:10.1063/1.4953547.
Smyth, A. G., Sarri, G., Doria, D., Kar, S., Borghesi, M., Vranic, M., Guillaume, E., Silva, L. O., Vieira, J., Amano, Y., Habara, H., Tanaka, K. A., Heathcote, R., Norreys, P. A., Hicks, G., Najmudin, Z., and Nakamura, H. 2016. "Magnetic field generation during intense laser channelling in underdense plasma". United States. doi:10.1063/1.4953547.
@article{osti_22598926,
title = {Magnetic field generation during intense laser channelling in underdense plasma},
author = {Smyth, A. G. and Sarri, G. and Doria, D. and Kar, S. and Borghesi, M. and Vranic, M. and Guillaume, E. and Silva, L. O. and Vieira, J. and Amano, Y. and Habara, H. and Tanaka, K. A. and Heathcote, R. and Norreys, P. A. and Hicks, G. and Najmudin, Z. and Nakamura, H.},
abstractNote = {Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.},
doi = {10.1063/1.4953547},
journal = {Physics of Plasmas},
number = 6,
volume = 23,
place = {United States},
year = 2016,
month = 6
}
  • No abstract prepared.
  • The results of a two-dimensional particle-in-cell simulation and of an analytical description of the propagation in an underdense plasma of a short, relativistically intense, laser pulse are presented. Self-focusing is proven in an ultrarelativistic regime for moderately long pulses. Pulses shorter than the plasma wavelength, but wider than it, excite a wake wave with a regular electric field. The electron density in the wake has a horseshoe'' shape and focuses a long pulse locally. The excitation of stimulated Raman backward scattering is observed.
  • Axial magnetic field generation by intense circularly polarized laser beams in underdense plasmas has been studied with three-dimensional particle-in-cell simulations and by means of theoretical analysis. Comparisons between analytical models and simulation results have identified an inverse Faraday effect as the main mechanism of the magnetic field generation in inhomogeneous plasmas. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach a maximum strength of several tens of megagauss for laser pulses undergoing relativistic self-focusing and channeling in moderately relativistic regime. Ultrarelativistic lasermore » conditions inhibit magnetic field generation by directly reducing a source term and by generating fully evacuated plasma channels.« less
  • The generation of both axial and azimuthal magnetic field components by the intense laser-dense plasma interaction and relativistic electron dynamics are studied in theoretical analysis and three-dimensional particle-in-cell simulations. For a circularly polarized laser, the cylindrical symmetry can be applied. Interacting with this laser, both axial and the azimuthally magnetic fields are generated and play an essential role in hot electron beam collimation, stabilization, and shaping. It is significantly different from the linearly polarized case, where the azimuthal current and the axial magnetic field are absent, therefore the axial current density gets filamentary early in the ramp plasma and ismore » focused into a single channel in the dense (with a density larger than the critical density n{sub c}) plasma later, and the electron and ion density distributions as well as the azimuthally magnetic field profile are broadened in the polarized direction to form an ellipse-like structure in the transverse plane. Instead, the results for the circularly polarized laser analytically and numerically show a much better collimation of the relativistic electron beams than in the case of the linearly polarized laser, due to the axial field component generated by azimuthal electron dynamics.« less
  • Based on the ten-moment Grad system of hydrodynamic equations, a self-consistent fluid model is presented for the generation of quasistatic magnetic fields in relativistic intense laser plasma interaction. In this model, the nondiagonal stress tensor is taken into account and the generalized vorticity is proved to be not conserved, which are different from previous ideal fluid models. In the quasistatic approximation, where the low-frequency phase speed v{sub p} is much smaller than the electron thermal speed v{sub te}, the axial magnetic field B{sub z} and the azimuthal one B{sub {theta}} are derived. It is found that the condition v{sub p}>>v{submore » te} used as the cold fluid approximation by previous papers is improper, where the derived B{sub z} is incomplete and one magnetization current for B{sub z} associated with the electron thermal motion does not appear. The profiles of both B{sub z} and B{sub {theta}} are analyzed. Their dependence on the laser intensity is discussed.« less