Onset of coherent electromagnetic structures in the REB–DT fuel interaction of fast ignition interest

Abstract

This paper focuses on the combinations of swiftly growing electromagnetic instabilities arising from the interaction of relativistic electron beams (REBs) with precompressed deuterium+tritium (DT) fuels of fast ignition interest for ICF. The REB–target system is taken as neutral in charge and current with distribution functions including target and beam temperatures. We also stress the significant impact, on the modes' growth rates (GRs), of mode–mode-coupling and intrabeam scattering. Collisional damping is documented at large wavenumbers in terms of inverse skin depth. A quasi-linear approach yields lower GR than linear ones. One of the most conspicuous outputs of the linear analysis are 3D broken ridges featuring the largest GR above k-space for an oblique propagation w.r.t. initial particle beam direction. The given modes are seen immune to any temperature-induced damping. Those novel patterns are easily produced by considering simultaneously Weibel, filamentation and two-stream instabilities. This behavior persists in the presence of smooth density gradients or strong applied magnetic fields. Moreover, in the very early propagation stage with no current neutralization in the presence of large edge density gradients, REBs demonstrate a characteristic ring-like and regularly spiked pattern in agreement with recent experimental results and previous simulations.