Abstract
Author(s): Diederichs, S; Benedetti, C; Esarey, E; Osterhoff, J; Schroeder, CB | Abstract: Acceleration of positron beams in plasma-based accelerators is a highly challenging task. To realize a plasma-based linear collider, acceleration of a positron bunch with high-efficiency is required, while maintaining both a low emittance and a subpercent-level energy spread. Recently, a plasma-based positron acceleration scheme was proposed in which a wake suitable for the acceleration and transport of positrons is produced in a plasma column by means of an electron drive beam [Diederichs et al., Phys. Rev. Accel. Beams 22, 081301 (2019)PRABCJ2469-988810.1103/PhysRevAccelBeams.22.081301]. In this article, we present a study of beam loading for a positron beam in this type of wake. We demonstrate via particle-in-cell simulations that acceleration of high-quality positron beams is possible, and we discuss a possible path to achieve collider-relevant parameters.
Highlights
Plasma-based particle accelerators potentially enable compact linear electron-positron colliders due to their large acceleration gradients [1]
We investigate beam loading of a positron bunch in the nonlinear wake formed in a plasma column with the goal of minimizing the energy spread of the bunch, while maintaining both a low emittance and a high charge
Assuming that in the vicinity of the axis the accelerating field can be modeled as EzðxÞ 1⁄4 Ez;0 − βjxj, where β describes the transverse gradient of Ez, from geometric considerations, we expect the relative slice energy spread at saturation to scale as σγ=γ ∼ βσr=Ez;0, and so σγ=γ → 0 in the limit of a small bunch
Summary
Plasma-based particle accelerators potentially enable compact linear electron-positron colliders due to their large acceleration gradients [1]. For a plasma column with a column radius smaller than the blowout radius, the transverse wakefields are altered, resulting in an elongation of the background plasma trajectories returning toward the axis This creates a long, high-density electron filament, leading to the formation of a wake phase region which is suitable for acceleration and transport of positron beams. We investigate beam loading of a positron bunch in the nonlinear wake formed in a plasma column with the goal of minimizing the energy spread of the bunch, while maintaining both a low emittance and a high charge. We further discuss the transport of the positron witness bunch and its optimization with the goal of minimizing the energy spread and preserving the emittance, both crucial parameters for the employment of this acceleration scheme in a future plasma-based linear collider. We assess a possible path to achieve colliderrelevant parameters
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