Resonant absorption instability

A new type of instability is demonstrated. It occurs when a space-charge wa ve develops along an electron beam that in turn propagates in a resonant me dium. The space-charge wave grows in space according to the loss associated with the resonance namely, it is directly related to the attenuation of a pure electromagnetic mode in the medium. The spatial growth is proportional to the square root of the current density and for a given current, it is i nverse proportional to the normalized momentum to the power of 1.5, i.e., ( gamma beta)(-3/2). (C) 2000 Elsevier Science B.V. All rights reserved.