Collective Focusing of Intense Ion Beam Pulses for High-energy Density Physics Applications
Authors: Mikhail A. Dorf, Igor D. Kaganovich, Edward A. Startsev and Ronald C. Davidson
Abstract: The collective focusing concept in which a weak magnetic lens provides strong focusing of an
intense ion beam pulse carrying a neutralizing electron background is investigated by making use of
advanced particle-in-cell simulations and reduced analytical models. The original analysis by
Robertson Phys. Rev. Lett. 48, 149 (1982) is extended to the parameter regimes of particular
importance for several high-energy density physics applications. The present paper investigates
(1) the effects of non-neutral collective focusing in a moderately strong magnetic field; (2) the
diamagnetic effects leading to suppression of the applied magnetic field due to the presence of the
beam pulse; and (3) the influence of a finite-radius conducting wall surrounding the beam
cross-section on beam neutralization. In addition, it is demonstrated that the use of the collective
focusing lens can significantly simplify the technical realization of the final focusing of ion beam
pulses in the Neutralized Drift Compression Experiment-I (NDCX-I) , and the conceptual designs of
possible experiments on NDCX-I are investigated by making use of advanced numerical
simulations. 2011 American Institute of Physics
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Submitted to: Physics of Plasmas (February 2011)
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