Comment on “Natural BNS damping of the fast ion instability”

Abstract

We show that the effect of BNS damping for the fast ion instability found in the recent paper “Natural BNS damping of the fast ion instability” [Phys. Rev. ST Accel. Beams 2, 044403 (1999)] occurs only when initial perturbations in the beam are amplified by many orders of magnitude, and, most likely, the linear approximation breaks down. We also demonstrate that the asymptotic solution found by Raubenheimer and Zimmermann gives a good approximation for the linear regime of the instability contrary to the statement of Pestrikov.