Status report on the Los Alamos proton storage ring

The proton storage ring currently operates at an average current of 30 μA corresponding to 1.25×1013 protons per pulse (ppp) at a repetition rate of 15 Hz. The design operating current for the machine is 100 μA. We are limited to running at the reduced yield because of beam losses during the accumulation period. These losses are understood and arise mainly from emittance growths during the injection and multiple scattering in the stripping foil during the storage. During beam studies we have succeeded in accumulating in excess of 3.7×1013 ppp. We have also observed a coherent transverse instability at high charge levels. The signture for the instability is rapid coherent growth of the transverse beam size followed by a loss of beam in the machine. The threshold for the instability depends most strongly upon rf voltage and beam size.