Fermilab, Batavia, Illinois, USA
At the Fermilab Booster, and many other proton facilities, an intense proton beam is accumulated by injection an H− beam through a stripping foil. The circulating beam scatters off the injection beam and large-angle Coulomb scattering leads to uncontrolled losses concentrated in the first betatron period. We measure the foil scattering rate in the Booster as a function of linac current, number of injection-turns, and time on injection foil. We find that current Booster operations has a 1% foil scattering loss rate and we make projections for the Proton Improvement Plan II (PIP-II) injector upgrade. We find that accurate modeling of the foil scattering loss must account for beam emittance in conjunction with the scattering rate and ring acceptance. Estimate of beam emittance at injection are discussed.
