Interaction of a rotational relativistic electron beam with a magnetized plasma

Abstract

In the presence of a uniform magnetic field, it is possible to form a hollow rotational relativistic electron beam which gyrates as a whole about its axis while propagating axially along the magnetic field. Here, the interaction of a rotational beam front with a dense magnetized plasma is studied. Starting from the two-fluid equations for the plasma, it is shown that under the conditions a2 − a1 ≫ λ, Ωe ≫ νe, and Ωi ≪ νi, where a2 − a1 is the beam thickness, λ is the plasma skin depth, Ω is the gyro frequency, and ν is the momentum transfer collision frequency, the beam current will not only be axially neutralized as usual but also angularly neutralized by a drift plasma current. The subsequent decay of these counter currents will in return induce upon the beam an axial retarding force capable of dissipating most of the beam axial energy in a few nsec. In addition to Ohmic heating the plasma electrons, a significant portion of the beam axial energy lost in the above manner will be transformed into ion energies through the action of a current sustained radial electrostatic field. Possible applications to plasma heating and beam trapping in astron type machines are discussed.