Extreme plasma-based compression for mega-amp, attosecond electron bunches at FACET-II

High-brightness, ultra-high peak current electron beams are of significant interest to applications including high-energy colliders, strong field Quantum Electrodynamics, and laboratory astrophysics. Despite such interest, compressing tightly-focused electron beams to attosecond pulse durations and mega-amp peak currents while preserving beam quality remains a challenge. Increased beam brightness amplifies collective effects such as Coherent Synchrotron Radiation, leading to beam degradation and limiting maximum possible compression. To achieve extreme beams while mitigating these effects, we present simulations that introduce an energy chirp to the beam using the large electric field gradient present in a plasma wakefield, which can produce chirps orders of magnitude greater than those found in conventional RF accelerators. We demonstrate these plasma-chirped beams can then be compressed in a chicane down to ~250 um durations with ~1 MA peak currents. The optimal beam and plasma conditions are investigated for different applications, with the objective of experimentally demonstrating this technique at the FACET-II facility at SLAC National Accelerator Laboratory. The trade-offs in beam parameters are explored with limitations on achievable final beam brightness evaluated. Insights gained from this study will help design the next-generation of high-brightness beams for new frontiers in scientific research.