Charge and current neutralization physics of a heavy ion beam during final transport

Abstract

Heavy ion fusion requires high power to be focussed onto a small pellet. If the reactor chamber pressure is below 10−4–10−5 Torr, beam compression will be limited by space charge unless neutralized by co‐moving electrons. If higher chamber pressures are used, the heavy ion beam will create a significant number of background electrons during its propagation and will undergo stripping. The background electrons could provide the neutralization required for high beam intensities. In this paper we will focus on the physics associated with propagation through a fully ionized hydrogen plasma, so background electron generation is not included. One‐dimensional electrostatic and two‐dimensional fully electromagnetic particle‐in‐cell simulations are presented.If a background plasma is present, we find that coinjected electrons whose purpose is to charge and current neutralize the ion beam become two‐stream unstable and no longer provide the thermally cool neutralization required. Further, we find that the ion induce...