An analytical method and practical verification for evaluating the undulator performance

The mechanical performance of an undulator has a significant effect on the on-axis magnetic field and thus a directly affect the performance of photon flux and stable operation in a storage ring. During the phase of mechanical design and construction, it becomes important to develop a method to evaluate the effects of magnetic fields caused by mechanical properties. This paper reveals a method to predict the distribution of a magnetic field utilizing the practice that mechanical performance combined with an ideal magnet assembly enables identification whether the magnet array structure is satisfactory. Moreover, the systematic errors expected from the mechanical inspection can be confirmed in the magnetic field measurement data. This scheme could be used to predict the systematic effects and then to apply effective remedies before the entire machine is completed.