Microstructure formation in radially counterstreaming electron flows
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A theoretical model is developed to describe the formation of microstructures due to plasma streaming instabilities in radially convergent geometries. Microstructures in the form of radial spokes are found experimentally in laser wakefield accelerators. The eigenvalues of a set of coupled linear ordinary differential equations are obtained and the complex wavenumbers calculated to give the local growth rates. The predictions are confirmed using particle-in-cell (PIC) simulations carried out for two counter-propagating converging/diverging plasma annuli. The simulations consistently demonstrate unstable growth for interactions between two counterpropagating annuli with different number densities. The growth rates obtained from the PIC simulations agree well with the growth rates from the semi-analytical model. The theory presented in this paper can provide powerful insight into converging plasma beams found in space and laboratory scale plasma.
Iñigo Gamiz , L I , Ersfeld , B , Brunetti , E , Yoffe , S R , Cairns , R A , Noble , A , Holt , G K & Jaroszynski , D A 2021 , ' Microstructure formation in radially counterstreaming electron flows ' , New Journal of Physics , vol. 23 , no. 4 , 043017 . https://doi.org/10.1088/1367-2630/abe8f6
New Journal of Physics
Copyright © 2021 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
DescriptionWe acknowledge the support of the UK EPSRC, Grant Number EP/N028694/1, and the EC's Laserlab-Europe H2020 EC-GA Nos. 654148 and 871124.
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