Progress on the Dipole Magnet for a Rapid Cycling Synchrotron

A rapid cycling hybrid synchrotron has been proposed for the acceleration of muons from 375 to 750 GeV. The bending in a hybrid synchrotron is created with interleaved cold and warm dipoles; the warm dipoles modulate the average bending field for the different particle momenta. A key challenge for the warm dipole magnets is the ramp rate, which is equivalent to frequencies of 400-1000 Hz. Recently a design has been suggested which employs 6.5 Si steel for the return yoke and FeCo for the poles. In simulations the design has shown a good performance (up to 2T) due to the FeCo and acceptable power losses by employing SiFe with a high Si content. The paper discusses the effect of eddy currents induced in the laminations and hysteresis effects on the field quality.