Superchanneling and Radiation of Ultrarelativistic Electron Beams in Disordered Porous Material

Transport of relativistic electron beams (REBs) in matter underpins a wide range of plasma, accelerator, radiation source, and material physics. Here we report a previously unexplored superchanneling regime of REB propagation in disordered porous materials composed of randomly structured solid-density thin skeletons and empty pores. Contrary to expected scattering or branching, the REB self-organizes into a dense stable filament while traversing these microstructures. This behavior arises from the interaction between the REB and randomly distributed hundred-kilotesla magnetic fields generated by localized return currents in the solid skeleton, representing a new collective mode of REB interaction with disordered media. Consequently, intense betatron oscillations of the superchanneled electrons yield collimated ultrabright GeV gamma rays with energy conversion efficiencies exceeding 40%. We analytically identify the parameter regime enabling REB superchanneling and derive the scaling laws of gamma-ray emission, validated by three-dimensional particle-in-cell simulations. Although achieving this regime requires tightly focused REBs, it is expected to be feasible in near-future experiments.