Creation and acceleration of DLA positrons in plasma channels

Direct laser acceleration of electrons in plasmas can provide 100s nC beams, by taking advantage of the electron guiding by the ion channel fields. The same acceleration principle can be applied to positrons, but only if the background fields can be reversed by electron beam loading. Here, we show that positrons can be created, injected and accelerated in a plasma channel. Positrons are generated when the laser interacts with a relativistic electron beam propagating at 90 degrees of incidence. We derive a semi-analytical estimate to determine the expected number of positrons. A direct acceleration of the positrons in the laser field is maintained over hundreds of microns in the plasma channel. We prove that positrons are guided along the channel main axis thanks to a high-charge self-loaded electron beam driven by the high laser intensity, and demonstrate the acceleration through DLA. Our proposal opens a path toward a new kind of compact and relativistic positron source, based on future-generation laser systems [1].

[1] B. Martinez et al, Phys. Rev. Accel. Beams 26, 011301 (2023)