Investigation of the power losses in a laminated dipole magnet with superconducting coils

Dynamic processes in a window-frame dipole with superconducting windings and a cold, laminated iron yoke have been investigated experimentally at JINR (Dubna, Russia), and theoretically at GSI (Darmstadt, Germany). The main aim of these investigations was a reduction of energy losses in the yoke during ramping. These losses are produced mainly by energy dissipation due to eddy currents and hysteresis effects in the laminations. Both effects were investigated theoretically. As a result, special end blocks were proposed to reduce eddy current losses. For eddy currents simulation we used a model developed at GSI and St. Petersburg State Polytechnical University (Russia). This model is based on an integro-differential approach to eddy currents in laminated structures and a volume integral method for the magnetization vector in ferromagnetic objects. To test this model, a series of experiments were performed at GSI on a normal conducting Heavy Ion Synchrotron dipole magnet. The magnetic field in the aperture of this magnet was controlled with a point coil during the current ramping in the winding. The same transient processes were simulated using software, developed on the basis of the integro-differential method. The theoretical calculations were in reasonable agreement with the measurements.