The theory and simulation of relativistic electron beam transport in the ion-focused regime

Abstract

Plasma wakefield effects on highcurrent relativistic electron beam transport in the ionfocused regimeSeveral recent experiments involving relativistic electron beam (REB) transport in plasma channels show two density regimes for efficient transport; a low-density regime known as the ion-focused regime (IFR) and a high-pressure regime. The results obtained in this paper use three separate models to explain the dependency of REB transport efficiency on the plasma density in the IFR. Conditions for efficient beam transport are determined by examining equilibrium solutions of the Vlasov-Maxwell equations under conditions relevant to IFR transport. The dynamic force balance required for efficient IFR transport is studied using the particle-in-cell (PIC) method. These simulations provide new insight into the transient beam front physics as well as the dynamic approach to IFR equilibrium. Nonlinear solutions to the beam envelope are constructed to explain oscillations in the beam envelope observed in the PIG simulations but not contained in the Vlasov equilibrium analysis. A test particle analysis is also developed as a method to visualize equilibrium solutions of the Vlasov equation. This not only provides further insight into the transport mechanism but also illustrates the connections between the three theories used to describe IFR transport. Separately these models provide valuable information about transverse beam confinement; together they provide a clear physical understanding of REB transport in the IFR,

Electron beam dynamics and self-cooling up to PeV level due to betatron radiation in plasma-based accelerators

“…inside a uniform ion channel in the blow-out and bubble regime [38], one can assume that the focusing constant is set to be the averaging value over the stage for solving the beam dynamics problem of large-scale laserplasma accelerators consisting of many stages within good approximation. Assuming that electrons undergo no excitation force from direct laser fields and/or instabilities such as hose instability in plasma waves, the envelope equation of the rms beam radius r is given by [51,52]…”

Synchrotron radiation from electron beams in plasma-focusing channels

“…The blow-out regime of the PWFA can be viewed as a short-bunch version of the ion-focused regime of electron beam propagation [16] - [19]. The "ion-focused regime" is a phrase traditionally applied to describe the propagation of long (compared to the plasma wavelength) electron beams in a plasma and, hence, these beams are subject to the electron-hose instability [20] - [23].…”

The dependence of microwave radiation from a beam-driven turbulent plasma on the beam-to-plasma density ratio

“…However, after passing the first focusing point, the amplitude of the beam envelope oscillation is much lower than that in the earlier stage. Swanekamp et al give a relation between the equilibrium radius and the transverse temperature of the beam as [19]. This relation is derived with an assumption that all of the beam electrons have the same total energy.…”