Observation and analysis of time-dependent closed orbit motion in the LAMPF proton storage ring

When the stored beam is artificially offset in a section of the LAMPF (Los Alamos Meson Physics Facility) proton storage ring by changing selected ring dipole strengths, there is evidence for a small time dependence of the offset during the course of beam injection. A complete discussion of the time dependence of orbit offsets should take into account at least the following possibilities: (1) correlations between the injection timing pattern and ring dipole field ripple, (2) correlations between the injection timing pattern and changes of beam position monitor characteristics, and (3) growth of space-charge effects as the number of stored protons increases. Since there are no a priori reason to expect the correlations mentioned, the authors have analyzed the observed time dependence of the beam offset in terms of space-charge effects only, although the other possible causes cannot be ruled out.<>