Evaluation of Eddy Currents Dependent on Excitation Pattern in Design of Pulse Electromagnets

Abstract

The evaluation of a new shift bump magnet for replacement of the J-PARC (Japan Proton Accelerator Research Complex) RCS (Rapid Cycling Synchrotron) confirmed that the measured magnetic field waveform was different from the excitation-current waveform. The reason for this is the eddy-current effect due to the fast trapezoidal excitation pattern of approximately 1.5 ms. The same result was confirmed by OPERA-3D. A high-precision injection-beam orbit that suppresses device radiation due to beam loss was necessary. Therefore, in the excitation waveform of the injection bump magnet, the variation range at the flat-top must be less than ±1.0%. We evaluated the effectiveness of the dynamic-magnetic field analysis of OPERA-3D comparison with the measurement results. An agreement with a 0.06% deviation in the magnetic field distribution, the effect of eddy currents on the magnetic field waveform, and the potential of the analysis software for system design were confirmed. We also calculated the amount of heat generated by the bump-magnet coil and the necessary measures for operation. Furthermore, we verified that probes can accurately evaluate the pulsed excitation waveforms.