The Theory of Final Focusing of Intense Light Ion Beams

Efficient transport of the high power light ion beams of interest to inertial confinement fusion experiments may require the use of large radius transport channels. The mismatch in the radii of the transported ion beam and the ICF target requires that the beam be focused following large radius transport. A theoretical description of intense light ion beam focusing with a z-discharge plasma is presented. The theory is based on a Vlasov equation description of a fully charge and current neutralized ion beam, neglecting any angular momentum of the beam ions. An initial ion beam phase space distribution with adjustable parameters is considered so that its effect upon the phase space distribution at the focal plane can be analyzed. A numerical code is used to analyze the effect of angular momentum on the focusing properties of the final focusing cell. The theoretical analysis indicates that the proposed focusing method is viable. The numerical analysis indicates that even if beam ions have a significant amount of angular momentum, the beam can still be focused as indicated by the zero angular momentum theory. Keywords Ion beams Inertial confinement fusion Final focusing Transport channels.