Long-term evolution of broken wakefields in finite-radius plasmas.

A novel effect of fast heating and charging a finite-radius plasma is discovered in the context of plasma wakefield acceleration. As the plasma wave breaks, most of its energy is transferred to plasma electrons. The electrons gain substantial transverse momentum and escape the plasma radially, which gives rise to a strong charge-separation electric field and azimuthal magnetic field around the plasma. The slowly varying field structure is preserved for hundreds of wakefield periods and contains (together with hot electrons) up to 80% of the initial wakefield energy.