An Analytical Model Connecting Spectral Multi-Species Modulations with Microscopic Electron-Properties in PW-Class Laser-Ion Acceleration

Spectral signatures of laser-accelerated ion beams are frequently used to characterize underlying acceleration mechanisms. Yet regularly, more than just one ion species are accelerated in experiments, e.g. from hydro-carbon contamination layers, multiple charge states or mixed materials. Such presence of multiple ion species (q/m) in the accelerating field leads to characteristic modulations in observed proton spectra due to electro-static repulsion during co-propagation. Resulting typical spectral modulations from these effects are presented with an analytical model for PW-class laser-ion acceleration. We improve previous predictions with explicit multi-species interaction for arbitrary mixtures, enabling us to connect important ensemble properties of laser-accelerated electrons with spectral signatures of accelerated ions. We support our new model with extensive particle-in-cell simulations and propose an experimental implementation with a novel cryogenic target, allowing systematic verification of our predictions in an environment without the strong influence of hardly controllable processes such as ionization dynamics.