Plasma-cascade instability

Abstract

In this paper we describe a new microbunching instability occurring in charged particle beams propagating along a straight trajectory. The nature of these exponentially growing plasma oscillations gave the reason for its name: plasma-cascade instability. Such instability can strongly amplify longitudinal microbunching originating from the beam s shot noise, even to the point of saturation. Resulting random density and energy microstructures can drastically reduce beam quality. Conversely, such instability can drive novel high-power sources of broadband radiation or can be used as a broadband amplifier. We discovered this phenomenon in a search for such amplifier in the coherent electron cooling scheme [Phys. Rev. Lett. 102, 114801 (2009)] without separation of electron and hadron beams. In this paper we present a brief analytical theory of this new phenomenon, detailed numerical studies, the results of experimental demonstration as well as control of the longitudinal plasma-cascade instability.