Eddy current and structural analysis of the beam pipe for the BRing dipole magnet

Abstract

Fast-ramping magnets will be used in the Booster Ring (BRing) of the High-Intensity Heavy Ion Accelerator Facility (HIAF), which is proposed by the Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS). The dipole magnet will provide the field quality from the injection field of 0.0496 T up to the maximum value of 1.5786 T, with the maximum ramping rate of 12 T/s. The ramping magnetic field induces eddy currents that give rise to eddy loss and large force on the beam pipe, field delay and sextupole field appear to affect the field quality provided by the BRing dipole. An in-detail understanding of these effects is an essential aspect of the design. Based on the finite-element analysis, a simplified model by use uniform background magnetic field was used to the transient simulations, eddy current and the forces on the pipe at different times on the beam pipe were performed. This paper presents the results obtained for the eddy loss and magnetic field delay for different wall thicknesses. Then, mechanical design details are presented, and also stress distribution, the deformation in the beam pipe. The analysis results revealed that the eddy current and thus the field delay and eddy current-induced Lorentz force scales linearly with the derivative of the magnetic field and the thickness of the pipe. The power losses that cause heating of the pipe is linear with the square of the derivative of the magnetic field and the thickness of the pipe.