Numerical proof-of-concept of nanofoam-based targets for proton acceleration and high-energy photon and positron generation in strong fields

A source of high-energy photons, ions, and positrons can be attained with the interaction of ultra-intense femtosecond laser pulses with advanced nanostructured targets. We present and characterise a numerical model that mimics the foam deposition process on solid substrates, as it occurs in Double-Layer Target (DLT) manufacturing. The model is integrated into Particle-In-Cell (PIC) simulations in full three-dimensional geometry to study electron acceleration, consequent high-energy photon emission, proton acceleration, and pair production with realistic target and laser parameters, focusing on Strong-Field Quantum Electrodynamics (SFQED) processes. We highlight the importance of realistic foam morphology modelling even at high-laser intensity and the need for specific optimisation of target parameters with realistic PIC simulations to improve radiation production efficiency. Our study shows that the DLT could be a compact multi-purpose scheme to achieve high-brightness photons and high-energy protons and to observe and optimise non-linear Breit–Wheeler pair production.