Effects of filamentation instability on the divergence of relativistic electrons driven by ultraintense laser pulses

Abstract

Generation of relativistic electron (RE) beams during ultraintense laser pulse interaction with plasma targets is studied by collisional particle-in-cell (PIC) simulations. Strong magnetic field with transverse scale length of several local plasma skin depths, associated with RE currents propagation in the target, is generated by filamentation instability (FI) in collisional plasmas, inducing a great enhancement of the divergence of REs compared to that of collisionless cases. Such effect is increased with laser intensity and target charge state, suggesting that the RE divergence might be improved by using low-Z materials under appropriate laser intensities in future fast ignition experiments and in other applications of laser-driven electron beams.

Growth of concomitant laser-driven collisionless and resistive electron filamentation instabilities over large spatiotemporal scales

“…The experimental and numerical data gathered so far seem to suggest that magnetic filaments only form relatively near the laser axis (over a few tens of microns), where the fast electron density, and therefore the overall plasma anisotropy, are initially at their highest. Furthermore, in contrast with simulation results [20,29], there has been as yet no observation of the simultaneous development of the collisionless and resistive variants of the instability in, respectively, the surface and inner regions of dense targets. Here, in contrast with previous studies, we present measurements and simulations demonstrating: (i) filamentary magnetic-field generation by fast electrons over much larger scales than previously thought possible, both in space (hundreds of microns, i.e.…”

“…Fast electrons, however, can also be prone to further filamentation when propagating through the target bulk. The resistive character of the cold plasma electrons making up the fast-electron-neutralizing return current [18] then leads to larger magnetic filaments [19] and enhanced fast-electron scattering [20]. Such resistive filamentation has been diagnosed either indirectly, from spatial modulations of the sheath-field-accelerated protons [21,22], or directly, from the optical emission induced by the fast electrons [23].…”

Filamentation Instability of Electromagnetic Beams in Nonlinear Media: A Tutorial Review

“…Several later references with similar logic and directly or indirectly concerned with instability have been published (Hao et al, 2013;Yang et al, 2016;Bawaaneh et al, 2010;Lin et al, 2014;Hasanbeigi et al, 2013;Fox et al, 2013;Sharma et al, 2016;Silantyev et al, 2017;Pathak et al, 2015;Grassi et al, 2017;Alimohamadi and Hajisharifi, 2017). Despite different approaches, the status of our understanding of instabilities has not changed appreciably over the years.…”

Stable transport of relativistic electron beams in plasmas

“…Collimated relativistic electron beams (REBs) with high energy are widely used in astrophysics, inertial confinement fusion (Craxton et al 2015;Yang et al 2016), plasma based accelerators (Geddes et al 2004;Esarey, Schroeder & Leemans 2009) and new diagnostic technologies (Barbieri et al 2000). In these areas, many potential application scenarios such as space active experiments (Marshall et al 2014;Borovsky & Delzanno 2019;Xue et al 2020) in the middle atmosphere require long-distance transport of electron beams.…”