Effect of Longitudinal Momentum Spread in Ion-Ripple Laser

Using kinetic coupling mode theory of three waves, the effect of longitudinal momentum spread in ion-ripple laser (IRL), which is an advanced new scheme to generate tunable-coherent radiation with frequency ranging from microwaves to x-rays, is investigated. For a Gaussian distribution in beam longitudinal momentum, the results show that the growth rate of IRL falls off rapidly with increasing momentum spread, and the momentum spread causes linear damping of beam space-charge wave, weakening the beam-radiation mode coupling and lowering the output radiation frequency apart from broadening the radiation spectrum. The dispersion relation and phase matching conditions are also obtained.