Double Beat-Wave Particle Acceleration

Described are two mechanisms which make it possible for an accelerated charged particle to stay in phase indefinitely with a moving accelerating potential well set up by electromagnetic radiation in a plasma beat-wave accelerator. 1) Double beat-wave mechanism, in which interference between two beatwaves cancel a) the fields in the interfering electromagnetic waves, b) the electron oscillations which would otherwise be set up by those waves. 2) Alternating density mechanism, in which one or each of two beat-waves set up resonant electron oscillations in alternate plasma regions, but not in others.