Determination of beam position and angle to minimize beam loss in the Los Alamos proton storage ring

A beam of negatively charged hydrogen ions passes through a stripper magnet to produce a neutral hydrogen beam before it is injected into the proton storage ring at the Los Alamos Meson Physics Facility. Inside the ring the injected beam passes through a carbon foil which strips off the remaining electrons to produce a proton beam. It is desirable to position the foil where it will minimize beam losses due to multiple Coulomb scattering in the ring. Beam loss is also decreased if the position and angle of the injected beam are chosen so that the phase ellipse of the injected beam has the best match with the phase ellipse of the ring beam. To achieve these two objectives, the position and angle of the injected beam must be determined at the foil. This is done by describing the beam path in the ring, and interpolating at the foil. A number of beam-position monitors placed at intervals around the ring provide data on the position of the beam at these points. A multiple-regression algorithm uses the data from the beam-position monitors to estimate the position and angle of the injected beam at the foil, along with correlation coefficients and confidence limits. (orig.)