Multi-PW laser-driven large-charge electron beam and intense electromagnetic pulse utilizing near-critical-density foams

We present an experimental study on electron acceleration and electromagnetic pulse (EMP) generation on the Shanghai Superintense Ultrafast Laser Facility. Using the 1.8-PW femtosecond laser pulse with a peak intensity of 8.0 × 1021 W/cm2 irradiating near-critical-density foam targets, enhanced electron acceleration is observed compared with the flat foil case, producing a high-quality electron beam with a large charge of 16.2 nC, a high temperature of 32.5 MeV, and a conversion efficiency from laser to electrons of 5.6% for energies more than 20 MeV. Simultaneously, an intense EMP with energy reaching up to 1.7 J is obtained for the foam target, which is seven times that of the flat foil case. The EMP spectra exhibit multiple peaks at fixed frequencies, where the EMP amplitude is directly proportional to the electron temperature for the electromagnetic radiation induced by electron reflux in the target holder and escape of hot electrons from the target, while it deviates from the proportional relationship for the eigenfrequency radiation of the vacuum chamber. This work demonstrates a novel scheme to simultaneously generate large-charge relativistic electron beams and intense EMPs, providing a multiphysics field condition for potential applications such as material property studies and device hardening.