  The 750-keV low-energy beam transport of the Los Alamos Neutron Science
Center (LANSCE) linac consists of two independent beam lines that facilitate
simultaneous injection of H+ and H- beams into the linear accelerator. The
efficiency of beam transport within this structure is largely controlled by the
effects of space-charge neutralization. In this paper, we report a series of
experiments that were performed to determine the level, as well as the required
timescale for the onset of beam space charge neutralization. Measurements
performed along the structure indicate significant variation of neutralized
space charge beam dynamics in the beamline, and the corresponding results have
been used to substantially improve beam transport with diminished beam losses.
The analysis of experimental and theoretical data employed in optimization of
beam performance in the transport line is discussed.
