Accelerating field enhancement due to ion motion in plasma wakefield accelerators

Abstract

Ion motion in plasma wakefield accelerators can cause temporal increase of the longitudinal electric field shortly before the wave breaks. The increase is caused by re-distribution of the wave energy in transverse direction and may be important for correct interpretation of experimental results and acceleration of high-quality beams.

Experimental study of extended timescale dynamics of a plasma wakefield driven by a self-modulated proton bunch

“…At the AWAKE nominal density of 7 × 10 14 cm −3 the relative bunch density is reduced, the bunch size is optimised for the plasma density (σ r = k −1 p ), and trajectory crossing does not occur. At the nominal density, it is rather expected that ion motion causes decay of the wakefield on extended timescales [28][29][30], an effect not observed in the simulations performed for this study.…”

Experimental Observation of Plasma Wakefield Growth Driven by the Seeded Self-Modulation of a Proton Bunch

“…Interestingly, the small ion density perturbation observed with xenon (Fig. 4f) has a positive effect on the amplitude of the wakefields [20,39,40].…”

Ion dynamics driven by a strongly nonlinear plasma wake

“…the ion dynamics has not attracted as much attention as other wakefield features, and has been studied mainly in the context of the wakefield lifetime [14][15][16][17][18] or the overall energy balance in the system [19]. However, the ion motion can result in formation of exotic, slowly changing plasma density profiles, which may be useful for diagnostics [19,20], driver guiding [1], beam stabilization [21,22], wakefield enhancement [23,24], radiation generation [25], or making field structure favorable for positron acceleration [26][27][28][29][30]. Ion density valleys or peaks can appear both in strongly nonlinear [31,32] and almost linear [14-18, 20, 33, 34] regimes and for all kinds of drivers.…”