High Average Gradient in a Laser-Gated Multistage Plasma Wakefield Accelerator

Plasma wakefield accelerators driven by particle beams are capable of providing accelerating gradient several orders of magnitude higher than currently used radio-frequency technology, which could reduce the length of particle accelerators, with drastic influence on the development of future colliders at TeV energies and the minimization of x-ray free-electron lasers. Since interplasma components and distances are among the biggest contributors to the total accelerator length, the design of staged plasma accelerators is one of the most important outstanding questions in order to render this technology instrumental. Here, we present a novel concept to optimize interplasma distances in a staged beam-driven plasma accelerator by drive-beam coupling in the temporal domain and gating the accelerator via a femtosecond ionization laser.

Figure 1

Sketch of acceleration stage (a) showing a PWFA, a chicane section to extract and insert new driver beams from the beam reservoir and a plasma lens to refocus the trailing beam onto the subsequent PWFA. The concept of laser gating is illustrated by a PIC snapshot, showing reservoir beam, drive beam, trailing beam, and a central cut through the plasma density. (b). The intensity of the fully resolved ionization laser is plotted in black. A sketch of the bunch-train configuration before the PWFA and after the subsequent chicane is shown in (c).

Figure 2

Trailing-beam delay accumulated in a chicane as a function of energy for different chicane designs, where the reservoir-beam delay is always kept at $230\mathrm{\mu }\mathrm{m}$ (a). Total length (red) and corresponding average gradient (black) of a staged laser-gated PWFA accelerator, depending on reservoir-beam energy and final trailing-beam energy are plotted in (b).

Figure 3

Transport of different beam types between plasma stages. Reservoir beams propagate in a FODO lattice and are not influenced by plasma wakes, as they arrive too early. Drive beams lose energy to the plasma wake and leave the plasma with increased divergence. The trailing beam is refocused by a plasma lens (thin blue area) between the PWFA stages (wide blue area). Mean trailing-beam energy gain is plotted as red line.

Figure 4

Numerical modeling of the longitudinal phase space at different locations. Trailing-beam distributions are plotted as initial state, after accelerating sections (top left) and as enlargement (top right). For driver and reservoir beams, macroparticle distributions are plotted combined with the current (bottom). All macroparticles are delayed following Eq. (1).