Ionization-induced laser-driven QED cascade in noble gases

Abstract

A formula for the ionization rate in extremely intense electromagnetic field is proposed and used for numerical study of QED (quantum-electrodynamical) cascades in noble gases in the field of two counter-propagating laser pulses. It is shown that the number of the electron-positron pairs produced in the cascade increases with the atomic number of the gas where the gas density is taken to be reversely proportional to the atomic number. While the most electrons produced in the laser pulse front are expelled by the ponderomotive force from region occupied by the strong laser field there is a small portion of the electrons staying in the laser field for a long time until the instance when the laser field is strong enough for cascading. This mechanism is relevant for all gases. For high-$Z$ gases there is an additional mechanism associated with the ionization of inner shells at the the instance when the laser field is strong enough for cascading. The role of both mechanisms for cascade initiation is revealed

Extreme plasma states in laser-governed vacuum breakdown

“…12-beams with an f-number of 1.2 with a total power of 15 PW, which roughly corresponds to an ideal e-dipole wave of 13 PW, interacted with a plasma target with a radius of 1 wavelength and a density of 10 22 cm −3 . The influence of ionization as well as ion motion on laser-plasma dynamics can be important, especially in case of high-Z elements 49 , 50 , as the process of triggering the electron-positron cascade can be governed by a proper choice of target parameters. However, for the case of interest we confined ourselves to solid hydrogen targets, assuming that it will be fully pre-ionized already at the leading edges of the pulses.…”

Particle trajectories, gamma-ray emission, and anomalous radiative trapping effects in magnetic dipole wave

“…In order to generate pair plasma by incoming laser pulses we must prepare a seed in the focal region to trigger vacuum breakdown. Here the seed can be an electron beam, a plasma or solid target, or a gamma ray (see for an example [35][36][37][38][39][40]). In general, this problem looks like the well-known air breakdown in a focused laser beam.…”

Pair production seeded by electrons in noble gases as a method for the laser intensity diagnostics

“…We will show that the intensity can be extracted within the domain 10 23 W/cm 2 I 10 26 W/cm 2 depending on the laser field configuration. Besides, we also consider free electrons instead of xenon atoms in order to demonstrate the advantage of the latter scenario due to more efficient acceleration of the inner-shell electrons [28][29][30][31]. We also note that positron production via the Breit-Wheeler process was considered as a method for the intensity diagnostics in Refs.…”