Effects of Relativistic Thermal Velocity Spread of Beam on Electromagnetic Instabilities in Fast Ignition

Abstract

We investigate the linear instability of electromagnetic modes caused by the interaction of a relativistic electron beam with a dense plasma, taking into account the relativistic thermal spread of the beam. To obtain a linear dispersion relation, the relativistic factor γ of the beam is expanded within the first order of the beam thermal spread. We show that growth rate becomes large when the relativistic thermal spread of the beam is taken into account. In addition, we discuss the effects of the relativistic beam thermal spread on growth rate and the wave number vector that yields the maximum growth.