SPECTRAL BROADENING AND THE SIDE-BAND INSTABILITY

We present an analysis of the sideband instability including the trans ient regime, both analytically for deeply trapped electrons and numeri cally for nonbunched initial conditions. We show that both the standar d ''deeply trapped electrons'' and ''exponential regime'' assumptions are most often irrelevant for describing realistic situations. We also compare the results of this low signal analysis to a biparametric num erical investigation on tapered and filtered systems. We show that tap ering must in general be assisted by filtering to prevent spectral bro adening. Moreover, spectral broadening is not related in a simple way to sideband inhibition, due to nonlinear mechanisms.