Beam Induced Depolarization in the Hermes Transversely Polarized Hydrogen Target

The HERMES polarized hydrogen target is situated in the HERA electron storage ring in Hamburg. For the transverse spin program at HERMES, the magnetic holding field of the target is perpendicular to the HERA positron beam. An unwanted consequence is that the beam-induced resonance between hydrogen hyperfine states with Δm_F = 0, which was previously forbidden, can occur. The shape and spacing of these resonances will be shown. In order to prevent these resonances from reducing the nuclear polarization in the target cell, a pair of correction coils has been added to improve the field homogeneity. The success of these measures will be demonstrated.