Driver-delay chicanes for a multistage plasma-based accelerator facility

Abstract

The SPARTA project aims to design a medium-sized accelerator facility that facilitates new experiments in strong-field quantum electrodynamics using plasma-based accelerators. For this, we need several plasma stages and, therefore, several drivers. Drivers can be either an ultra-relativistic charged particle beam or a high-intensity laser beam. In case we use particle beams, we need a method of distributing these beams from a radio-frequency accelerator to the different plasma stages. A central part of this is a delay scheme that ensures temporal synchronization of the drivers. In this paper, we demonstrate how to achieve a 2 ns delay in $\sim$12 m, while keeping the first-order beam parameters periodic.

Figures (7)

• Figure 1: Sketch of a possible beam-driven SPARTA facility. The plasma stages are represented by the blue rectangles. The trailing bunch and the bunch train containing the drivers are accelerated by either a common, or two different, RF linacs (one common RF linac is shown here). An RF deflector (red rectangle) after the driver beamline (orange rectangle) separates every other driver into two different delay chicanes, allowing the fast kicker (green rectangle) to operate at a feasible bunch separation. The septum magnet is illustrated with the pink rectangle. At the downstream end, the accelerated trailing bunch would be used in beam--laser collisions with a petawatt-level (PW) laser.
• Figure 2: Sketch of the drive-train configuration with a trailing bunch coming out of the RF linac. The space between the trailing bunch and the last (most upstream driver) is synchronized for optimal acceleration in the plasma stage, while the distance between the drivers are all $\frac{\Delta t}{2}$. The direction of propagation is to the right, as indicated by the arrow.
• Figure 3: A sketch of dipoles and straight sections illustrating how the different variables of Eq. \ref{['eq:Delta-Ls']} are defined.
• Figure 4: The horizontal orbit (top) of the delay chicane. The beamline lattice (bottom) follows the convention, where rectangles above the central axis have positive fields or are focusing in the horizontal plane, for dipoles and quadrupoles respectively. The achieved delay over a single chicane is 2ns for 2GeV, and all field strengths (or equivalent) are given in Table \ref{['tab: parameter values']}. Note that the length of the indicated elements are not to scale to their actual lengths in the simulated lattice---only their mid-points are at the correct longitudinal location.
• Figure 5: Evolution of (a) the horizontal $\beta$-function; (b) the vertical $\beta$-function; (c) the horizontal first-order dispersion; and (d) the longitudinal dispersion. All parameters shown are periodic, which is necessary for a repeating lattice.