Final beam transport in HIF

Heavy ion beams (HIBs) are transported through a reactor chamber gas to a fuel pellet in heavy ion fusion. Due to the HIB high current, the HIB space charge should be neutralized in a reactor, and promising final transport schemes have been proposed. In this paper, we discuss the final transport in a neutralized ballistic final beam transport scheme, and point out a new mechanism of the HIB divergence by an ambipolar (plasma sheath) field generated by neutralizing electrons. The paper also proposes possible solutions to suppress the HIB divergence by the ambipolar field and presents a transportable window.