Numerical simulation of ion beam propagation in Z-pinch plasma channels

Abstract

Propagation of intense ion beams in preformed z-pinch plasma channels, a scenario of interest for inertial confinement fusion devices, has been studied with a 2½-dimensional (r, z, vr, vθ , vz; ∂/∂θ = 0) hybrid simulation model. In the code, ions are represented by particles and electrons by an inertialess thermal fluid which obeys a generalized Ohm's law. Fields are solved in the quasi-neutral Darwin approximation. Several collisional and atomic processes are included. The simulations of this paper are performed with collisional effects scaled down by a factor of ten. The results are then extrapolated to estimate that propagation efficiencies in the 70% range are possible using 5–7 MeV, 1–2 MA proton beams with initial divergences in the range of 1.5° to 7° in a 4-m hydrogen channel. Current neutralization in excess of 99% is found, and no gross axisymmetric instabilities are observed.