Beam-plasma interaction in Astron

Abstract

The beam-plasma interactions in the Astron device are examined utilizing a model which consists of a homogeneous, cold, relativistic electron beam (E-layer particles) streaming through a Maxwellian plasma normal to a uniform external magnetic field. Using linear stability analysis the model shows that the strongest interactions occur at beam harmonics in the vicinity of the plasma normal modes which are near the upper hybrid frequency, and above each subsequent multiple of the plasma electron cyclotron frequency. The possible stabilizing effects of collisions between plasma electrons and background neutral particles, as well as the energy spread for beam particles are also examined. It is shown that collisional effects are especially strong at collision frequencies of the order of the beam cyclotron frequency and that the combined effects of collisions and energy spread may lead to quenching of the unstable modes. Comparison of the analytical results with experimental observations is presented and discussed.