Two-dimensional particle-in-cell simulation for magnetized transport of ultra-high relativistic currents in plasma

Nonlinear channel dynamics and magnetized transport of relativistic electron currents in plasma have been investigated, using transverse two-dimensional particle-in-cell simulations allowing for movable ions and fully relativistic binary collisions. Current filaments self-organize in coaxial structures where the relativistic beam in the center is surrounded by magnetized vacuum and a thin return current sheath outside. The current sheath explodes radially. The filament as a whole is current-neutral with almost vanishing magnetic field at the outside. Ion dynamics play an important role, leading to enhanced self-pinching of the filament cores. Collisional effects become significant in the slowly moving return currents. It is shown that electron currents of 100–1000 MA can be transported through dense plasma, but only through a large number of current filaments, each carrying about one Alfvén current. This aspect is essential for relativistic electron transport in fast ignition of targets for inertial confinement fusion (ICF).