Article

# Magnetic field calculations including the impact of persistent currents in superconducting filaments

CERN, Geneva

IEEE Transactions on Magnetics (Impact Factor: 1.21). 04/2002; DOI: 10.1109/20.996213 Source: IEEE Xplore

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**ABSTRACT:**Brookhaven National Laboratory (BNL) has built a prototype superconducting dipole for the Facility for Antiproton and Ion Research (FAIR) at GSI that can be ramped at a high rate (1-4 T/s). To characterize the field quality at such high ramp rates, a measurement system consisting of 16 printed circuit windings was developed. In this system, the signals induced in all the windings as the magnet is ramped are analyzed to obtain the field harmonics. Initial measurements with this system suffered from somewhat poor resolution of the ADCs used for data acquisition. Also, only a few low order harmonics could be obtained with the 16 signals. These drawbacks have been addressed by replacing the ADCs with HP3458A voltmeters and by combining data taken with two different orientations of the probe. This has allowed us to measure very precisely (10 ppm of the dipole field) all the harmonics up to the 26-pole at ramp rates up to 4.3 T/s. The data analysis and results with this improved system are presented.IEEE Transactions on Applied Superconductivity 07/2008; · 1.32 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Magnetic field changes in the coils of superconducting magnets are shielded from the filaments' core by so-called persistent currents which can be modeled by means of the critical state model. This paper presents an semi-analytical 2-dimensional model of the filament magnetization due to persistent currents for changes of the magnitude of the magnetic induction and its direction while taking the field dependence of the critical current density into account. The model is combined with numerical field computation methods (coupling method between boundary and finite elements) for the calculation of field errors in superconducting magnets. The filament magnetization and the field errors in a nested multipole corrector magnet have been calculated as an example.01/2005; - [Show abstract] [Hide abstract]

**ABSTRACT:**The dipole magnets for the new heavy-ion synchrotron SIS-100, planned within the Facility for Anti-Proton and Ion Research (FAIR) at GSI, Darmstadt, Germany, have to be optimized under certain design requirements. At the intended high beam intensities, the field quality in the aperture is crucial. The geometry of the window-frame magnet featuring superconductive coils was already optimized with respect to the field quality in terms of higher-order multipoles using static 2D and 3D Finite Element (FE) simulations. During fast ramping up to 2 T, however, additional perturbations arise due to local saturation and due to eddy currents in both the yoke and the metallic beam pipe. These have already been investigated using transient 2D FE simulations. In order to further refine these results, a transient nonlinear 3D FE model, capturing the eddy-current effects at the end plates is used. The results are compared to those obtained by static simulations.IEEE Transactions on Applied Superconductivity 07/2009; · 1.32 Impact Factor

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