  The Rapid Cycling Synchrotron (RCS) in Chinese Spallation Neutron Source
(CSNS) accelerates proton beam from 80Mev to 1.6GeV at a repetition rate of
25Hz. All dipole magnets of RCS are operated at AC with biased DC. Aiming at
the properties of these dipole magnets, we take some methods to improve
magnetic field quality in the good region and reduce eddy currents in the iron
core . In this paper, we would present the process of the magnet design and
temperature rise calculation. At the same time, the field measurement results
and temperature test of the prototype magnet are also described and discussed.
