Mechanical characterization of an APPLE undulator at TPS

Abstract

Because of a strong demand for circularly polarized radiation, elliptically polarized undulators (EPU) are widely used in synchrotron light source nowadays. At Taiwan Photon Source (TPS) with a 3-GeV ring, the EPU plays an important role to fulfill the needs of the user community for EUV to soft X-ray. Up to phase II, in total five EPU have been installed. Because multiple operating modes are necessary, the EPU suffers changes in attractive and repulsive forces in three directions, in contrast to a general ID, which suffers only a vertical attraction. A mechanical structure of the EPU is required that can withstand multiple stresses and eliminate mechanical deformation. In addition, the EPU, a purely magnetic structure, is sensitive to high-permeability material, which makes the overall structure a heterogeneous material, resulting in a problem with uneven thermal expansion and contraction because of changes in ambient temperature. Here we discuss and propose solutions to resist force and temperature variations of EPU mechanical structures, which includes mechanical simulation and inspection.