Ion-channel guiding in a steady-state free-electron laser

Abstract

Ion-channel guiding of an intense relativistic electron beam in a microwave (cm--mm) steady-state free-electron laser (FEL) is proposed. By averaging equations of motion over the high-frequency variation of the radio-frequency field, the expulsion mechanism of plasma electrons is examined and a criterion to allow development of an ion channel in a steady-state FEL is derived. Key issues on FEL operation induced by ion-channel guiding are discussed.