EFFECTS OF A NONUNIFORM BEAM VELOCITY IN A CHERENKOV LASER

We consider a two-dimensional model of the Cherenkov laser in which th e electron beam is confined in the direction of its drift by a suffici ently large magnetostatic field. For this model, taking into account t he nonuniformity of the drift velocity across the beam thickness, we h ave analyzed the growth of the electromagnetic power and the decrease in the drift velocity of the electron beam. We have also investigated the effect of the nonuniform drift velocity on energy transfer from th e electron beam to the electromagnetic wave. The main results obtained from numerical analysis are as follows. The nonuniform drift velocity of the electron beam causes it to separate into two regions: one main ly contributes to the growth of the electromagnetic wave while the oth er does only slightly. The boundary of these two regions has been foun d to coincide with a plane on which the product of the wave number of the electromagnetic wave and the drift velocity of the electron beam i s approximately time-invariant. In addition, the optimum beam thicknes s, which predominantly contributes to the growth of the electromagneti c wave, corresponds to half of the reactive skin depth of the electron beam. According to these results, for an efficient use of the electro n beam, the beam thickness in the Cherenkov laser should be chosen to be smaller than the optimum value obtained above. (C) 1997 Scripta Tec hnica, Inc.