LANSCE-linac beam-centroid jitter in transverse phase space

In order to characterize the beam-centroid jitter in transverse phase space, sets of position data of the 100-MeV H⁺ beam and 800-MeV H beam were taken in the transport lines of the Los Alamos Neutron Science Center (LANSCE) accelerator complex. Subsequent data evaluation produced initially puzzling inconsistencies in the phase-space plots from different pairs of beam-position monitors (BPMs). It is shown that very small random measurement errors will produce systematic differences between plots that should nominally be identical. The actual beam-centroid jitter and rms BPM measurement errors can be deduced from the data, and simulations can validate the deductions. The phase-space plots can also reveal the presence of problem beamline components. Examples will be shown.