Ultraintense Laser-Produced Fast-Electron Propagation in Gas Jets

Abstract

We study the propagation of fast electrons in a gas at different densities. A large relativistic electron current is produced by focusing a short-pulse ultrahigh-intensity laser on a metallic target. It then propagates in a gas jet placed behind the foil. Shadowgraphy in the gas shows an electron cloud moving at sub-relativistic average velocities. The experiment shows (i) the essential role of the density of background material for allowing propagation of fast electrons, (ii) the importance of the ionization phase which produces free electrons available for the return current, and (iii) the effect of electrostatic fields on fast-electron propagation.

LASER-driven fast electron dynamics in gaseous media under the influence of large electric fields

“…Also, such diagnostics allowed following the initial phase of expansion, which was not easily reconstructed in Ref. 7. Indeed, although the model predicted expansion velocities of the order of c / 30− c / 10, in agreement with the average velocities from the experiment, in Ref.…”

“…7. In the case of Ar, this corresponded to 10 19 and 3 ϫ 10 19 atoms/ cm 3 , for backing pressures of 30 and 80 bars, respectively.…”

Beam plasma electromagnetic instabilities in a smooth density gradient: Application to the fast ignition scenario

“…Such a scenario therefore prompts the need for a nonlinear investigation of TSF evolution while doing the same for TS is less important and for F irrelevant. But other scenarios with larger beam densities should also be considered for FIS, 7 and this can dramatically affect the order of precedence of growth rates at the beginning of the density gradient. 19 ACKNOWLEDGMENT This work has been partially achieved under Project No.…”

Generalized Ohm’s Law for a Background Plasma in the Presence of Relativistic Charged Particles

“…(6). For the case of electron beams in foam or gas targets [19], we stress that the conditions (9) must apply, in particular, the beam density must be much lower than the background density. When this is not the case, the resistivity must be modified because the isotropic component of the background distribution function becomes strongly non-Maxwellian [20].…”