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Abstract

Intense high-energy particle beams are used in fundamental sciences, material sciences, relativistic laboratory astrophysics, and in the industry. Traditionally, dense collimated multi-GeV photon and electron-positron beams are generated via bremsstrahlung and Bethe-Heitler (BH) electron-positron pair creation, respectively. Recent research has focused on strong-field QED processes for greatly enhancing the flux and intensity of the generated beams. To determine the relative role of collisional and strong-field QED processes, we implemented bremsstrahlung and BH pair production processes in the particle-in-cell code Smilei. Using simulations, we show that a high-current ultrarelativistic electron beam interacting with a submicrometer-thick conducting foils can undergo strong self-focusing accompanied by efficient emission of gamma-ray photons. We study the effect of varying electron beam shape, radius and length on the final radiated energy. We show that the self-generated fields can be strong enough that emission occurs in the strong-field QED regime, where a single emitted photon can carry away a significant fraction of the emitting electron energy. We demonstrate that, after beam collision with multiple foils, femtosecond collimated electron and photon beams with particle number density exceeding that of a solid are obtained. This study is timely as it enables laserless strong-field QED investigations with a single high-current electron beam, particularly relevant for the upcoming FACET II facility.