BEAM DYNAMICS STUDIES WITH THE HEAVY-ION LINEAR INDUCTION ACCELERATORMBE-4

Current amplification of heavy-ion beams is an integral feature of the induction linac approach to heavy-ion fusion (HIF). in this paper we report on amplification experiments conducted on a single beam of the Multiple Beam Experiment (MBE-4), a heavy-ion (Cs+) induction linac. E arlier MBE-4 experiments [H. Meuth et al., Nucl. Instrum. Methods Phys . Res. A 278, 153 (1989)] had demonstrated up-to-9X current amplificat ion but had been accompanied by an up-to-2X increase of normalized tra nsverse emittance. Experiments to pinpoint the causes of this emittanc e growth indicated various factors were responsible, including focusin g aberrations and mismatch difficulties between the injector diode and the accelerator transport lattice, a localized quadrupole misalignmen t problem, and the interaction of transversely large beams with the no nlinear elements of the focusing lattice. Following ameliorative measu res, new current amplification experiments, both with and without acce leration, showed that current amplifications of up to 3X and line char ge density increases of up to approximate to 2X could be achieved with out increasing the beam's normalized transverse emittance. Finally, bo th the transverse beam dynamics, and beam current and energy measureme nts were accurately modeled by numerical particle-in-cell simulations and longitudinal dynamics codes, respectively. (C) 1997 American Insti tute of Physics.