Electron trapping and acceleration across a parabolic plasma density profile

Abstract

It is known that as a laser wakefield passes through a downward density transition in a plasma some portion of the background electrons are trapped in the laser wakefield and the trapped electrons are accelerated to relativistic high energies over a very short distance. In this study, by using a two-dimensional (2D) particle-in-cell (PIC) simulation, we suggest an experimental scheme that can manipulate electron trapping and acceleration across a parabolic plasma density channel, which is easier to produce and more feasible to apply to the laser wakefield acceleration experiments. In this study, 2D PIC simulation results for the physical characteristics of the electron bunches that are emitted from the parabolic density plasma channel are reported in great detail.

Shock-Front Injector for High-Quality Laser-Plasma Acceleration

“…While this scheme has been studied theoretically [20,21] in great detail, first experimental attempts, where the transition was created by a second, perpendicularly propagating laser pulse arriving before the main pulse, have not been able to produce stable, monoenergetic electron bunches [22,23], possibly due to the transition being longer than p . Recently, a new approach to produce these sharp transitions by shock fronts in supersonic flows has been presented [24].…”

“…In contrast to slow downramps, sharp downward density jumps with a scale length of p or even shorter enable a fundamentally different injection process [20][21][22][23][24]. To understand and illustrate the process, we have performed three-dimensional particle-in-cell (PIC) simulations with the codes ILLUMINATION [25] and VORPAL [26] using the measured density profile and parameters matching the presented experiments.…”

“…Alternative approaches for injection aiming at both the stabilization and control of the process typically prevent self-injection by choosing a laser intensity and background plasma density below the self-injection threshold, while still driving a strongly nonlinear plasma wave [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In the colliding pulse scheme, a beat wave between the main laser pulse driving the plasma wave and an additional, counterpropagating pulse heats some of the electrons at the collision point such that they gain enough momentum to be trapped [11][12][13].…”

Injection and staging for laser plasma accelerators

“…If the scale length of the density down-ramp is less than the plasma wavelength [36,37,38], simulations show that trapping can occur without transverse wavebreaking and the beam quality improved [39]. Injection using a short down-ramp was demonstrated using the shock front arising from a razor blade placed above a gas jet [5].…”

Electric and magnetic wakefields in a plasma channel

“…Earlier workers have reported simulation studies on wakefields generated in wide parabolic plasma channels [17,18]. The present paper is devoted to a detailed analytical study of plasma wakefield generation in a parabolic plasma channel.…”