Polarization experiments at proton storage rings

A review is presented of polarization experiments in proton storage rings. Efforts to investigate narrow structures in pp scattering ("dibaryon resonances") by means of stored polarized beams are discussed. Tests of an internal polarized hydrogen gas target at the Heidelberg TSR, and demonstration of a spin filter, are summarized, followed by an overview of the experimental program with polarized beams and polarized internal H gas targets at the IUCF storage ring ("Cooler"). Reliable operation of a polarized H gas target based on the storage-cell method has permitted measurements of pp spin correlation parameters over a wide range of angles from 200 MeV to 450 MeV with small statistical and systematic errors. The characteristics of the polarized target and the methods of polarization reversal of the proton beam are discussed. Longitudinal polarization of the stored proton beam has recently been achieved.