Generation of focusing ion beams by magnetized electron sheath acceleration

Abstract

We present the first 3D fully kinetic simulations of laser driven sheath-based ion acceleration with a kilotesla-level applied magnetic field. The application of a strong magnetic field significantly and beneficially alters sheath based ion acceleration and creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath. The first stage delivers dramatically enhanced acceleration, and the second reverses the typical outward-directed topology of the sheath electric field into a focusing configuration. The net result is a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The predicted improvements in ion source characteristics are desirable for applications and suggest a route to experimentally confirm magnetization-related effects in the high energy density regime. We additionally perform a comparison between 2D and 3D simulation geometry, on which basis we predict the feasibility of observing magnetic field effects under experimentally relevant conditions.

Enhanced target normal sheath acceleration with a grooved hydrocarbon target

“…One of the possible approaches is to modify the laser pulse in order to create a pre-plasma with an optimal scale length 22,23 or to optimize the electromagnetic interference pattern 24 . Another way forward is to apply an external magnetic field, which results in a converging sheath field by confining the electron trajectories (in the transverse direction) leading to higher cut-off energy of accelerated protons/ions 25,26 . However, the strength of the magnetic field needed is enormous and is not easily achievable.…”