Coherently Enhanced Radiation Friction in Laser-Plasma Collisions

We reconsider the footprints of radiation friction in a head-on collision of a bunch of relativistic charged particles with a laser pulse by demonstrating that forward and backward radiation and radiation friction are coherently enhanced in a dense bunch. This opens an avenue to observe radiation friction in laser-matter interactions at much lower energies and laser intensities than previously considered possible. An estimate for the energy losses of the particles in the bunch over the collision due to coherent radiation friction in terms of laser and bunch parameters is derived and validated by comparing with the results of three dimensional particle-in-cell simulations.