Compact ultrafast intense LWFA-driven crystal-based source of $γ$-radiation, positrons and neutrons

Abstract

Compact sources of intense $γ$-rays, positrons and neutrons can bring radiation and particle-beam capabilities to small university-scale laboratories that would otherwise rely on large accelerator facilities. Here we propose and simulate a compact, laser-driven source that combines laser plasma wakefield acceleration (LWFA) with oriented crystalline targets to enhance the conversion of relativistic electron beams into high-energy photons and secondary particles. Electrons aligned with major crystallographic directions undergo coherent interactions, including channeling radiation and coherent bremsstrahlung, producing substantially enhanced photon emission compared with amorphous targets. Moreover, the strong angular-spectral correlation of the emitted radiation enables the generation of collimated $γ$-ray beams with reduced spectral bandwidth. Consequently, crystal-enhanced emission can increase particle-production efficiency, namely that of positrons through $γ$ conversion into electron-positron pairs and of neutrons through photonuclear reactions. Using Geant4 simulations, we investigate electron energies of 300 MeV, 1 GeV and 3 GeV interacting with an oriented tungsten crystal. Crystal orientation increases the $γ$-ray, positron and neutron yields by up to a factor of $\sim2$, reaching production rates of $\sim10^{24}γ/s$, $\sim10^{23}e^+/s$ and $\sim10^{21}neutrons/s$ for a 200 pC electron bunch with a duration of a few fs. The collimated $γ$-ray brightness reaches $\sim10^{24}γ/s/mm^2/mrad^2/0.1\%BW$, with an enhancement of 6-8 compared with random crystal alignment. We further demonstrate tunable quasi-monochromatic radiation through coherent bremsstrahlung in a thin diamond crystal, reaching a brilliance of $\sim3.5\cdot10^{20}γ/s/mm^2/mrad^2/0.1\%BW$. Furthermore, we discuss the potential applications of the technique proposed.