Magnetic field simulation of in-vacuum permanent magnet multipole wiggler

Abstract We present the magnetic field simulation and design of a high-field permanent magnet-based in-vacuum multipole wiggler for the Siam Photon Source (SPS). SPS utilizes a 1.2-GeV electron storage ring with a double-bend achromat (DBA) lattice, featuring four long straight sections capable of accommodating insertion devices up to 5 m in length. To generate tender and hard X-ray radiation in this low-energy storage ring, an in-vacuum permanent magnet multipole wiggler is designed as a cost-effective alternative to superconducting wigglers, which are expensive to operate and maintain. The magnetic period, pole dimensions, and ending magnets are optimized using the Radia code, considering the maximum available size of NdFeB magnets from the supplier and a magnetic gap of 15 mm. The first and second field integrals are minimized by adjusting the ending magnets. The simulated magnetic force, peak field, and field integrals as a function of the magnetic gap are presented. The Python-based Radia simulation results are consistent with those obtained using Mathematica and are visualized on a common platform.