Interplay of collisions with quasilinear growth rates of relativistic electron-beam-driven instabilities in a superdense plasma

Abstract

We focus attention on the rapidly growing electromagnetic instabilities arising in the interaction of intense and relativistic electron beams (REB) with supercompressed thermonuclear fuel. REB-target system is considered neutralized in charge and current with a distribution function including beam and target temperatures. The electromagnetic filamentation (Weibel) instability is first considered analytically in a linear approximation. Relevant growth rates parameters then highlight density ratios between target and particle beams, as well as transverse temperatures. Significant refinements include mode-mode coupling and collisions with target electrons. The former qualify the so-called quasilinear (weakly turbulent) approach. Usually, it produces significantly lower growth rates than the linear ones. Collisions enhance them slightly for kc/omega(p) < 1, and dampen them strongly for kc/omega(p) < 1. In a low temperature target plasma, intrabeam scattering also contributes to the instability taming, while keeping it close to zero in a warm plasma. Our numerical exploration provides further support to the cone-angle configuration (Osaka experiment) with REB penetrating close to the dense core of superdense deuterium + tritium fuel.