Handling the effects of eddy currents in CELSIUS

The CELSIUS ring in Uppsala will be used as a combined storage ring and synchrotron. The bending magnets being made of solid steel, high eddy currents will be induced while the magnetic field is changed rapidly. The eddy currents will delay the change of the field in the magnets and disturb the field distribution. The correction is an iterative procedure where each iteration includes measurement of field and field distribution during a machine cycle, calculation of differences between measured and desired values, and control of the current of the power supplies so that a better result is obtained in the next machine cycle. A description is given of the measurement system and the results obtained to date.