Spin-polarized atomic hydrogen is used as a gaseous polarized-proton target
in high-energy and nuclear-physics experiments operating with internal bea
ms in storage rings. When such beams are intense and bunched, this type of
target can be depolarized by a resonant interaction with the transient magn
etic field generated by the beam bunches. This effect has been studied with
the HERA positron beam in the HERMES experiment at DESY. Resonances have b
een observed and a simple analytic model has been used to explain their sha
pe and position. Operating conditions for the experiment have been found wh
ere there is no significant target depolarization due to this effect. [S003
1-9007(98)08340-9].