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P: Fachverband Plasmaphysik

P 13: Laser Plasmas I

P 13.2: Vortrag

Donnerstag, 23. März 2023, 11:30–11:45, CHE/0089

Influence of plasma profile on injection dynamics in a proton-driven wakefield accelerator. — •Pablo Israel Morales Guzmán, Patric Muggli, and John Farmer — Max-Planck-Institut für Physik

Plasma wakefield accelerators (PWFA) have been proposed as a novel technique to accelerate particle bunches to high energies. Due to the high electric fields supported in plasma, this can be done in a shorter distance than in conventional accelerators. PWFA use a relativistic particle bunch to drive wakefields. When the bunch density is much larger than the plasma density, it induces a non-linear plasma response. For negatively charged bunches, there is blow-out of plasma electrons. For positively charged ones, plasma electrons flow towards the axis, creating a high-density filament. This filament sustains defocusing fields for negatively charged bunches.

A proton bunch much longer than the plasma wavelength drives high-amplitude wakefields only after undergoing self-modulation (SM). SM transforms it into a microbunch train that resonantly drives wakefields. An electron bunch can be injected to seed SM or be accelerated.

We present results of a numerical study using particle-in-cell simulations with parameters similar to those of the AWAKE experiment. We show that along the low density ramp leading to the plasma entrance, the proton bunch generates a filament of plasma electrons. These results indicate that the accelerator plasma of future experiments relying on self-modulation, and a drive and accelerated bunch of different charge, cannot have a density ramp.