Measurement of H0 excited states produced by foil stripping of 800-MeV H- ions

Foil stripping of H^- directly to H⁺ is being considered for proton injection in the next generation of high-current proton storage rings. This technique can result in significant losses because excited states of H⁰, which are also produced in the foil, are field stripped in the downstream bending magnets. Without due care in the injection system design, many of the resulting protons will be outside the acceptance of the storage ring and will be quickly lost. We measured the production of such H⁰ excited states at the LAMPF High Resolution Atomic Beam Facility. An 800-MeV H^- beam was passed through carbon foils of thicknesses 70, 100, 200, and 300 μg/cm² and the excited states were analyzed by a special magnet downstream of the foil. The magnet had a linear field gradient so that the trajectories of the outgoing protons could be used to reconstruct the field values at which the various H⁰ stripped. We found that about 1% of the H⁰ emerge in excited states which can be stripped to protons by ring-bending magnets