A double-period in-vacuum undulator moving in three directions

Abstract The Shanghai High Repetition Rate XFEL and Extreme Light Facility (SHINE) previously designed a double-period undulator based on magnetic compensation technology, in which two undulators with different period lengths are mounted on the same base, and the undulator can be switched by lateral moving. However, the undulator is located outside the vacuum, and can only move up and down to adjust the gap, can not move along the longitudinal to adjust shift. In this paper, based on the improvement of the above undulator, a new double-period in-vacuum undulator is designed, which can move in vertical, lateral and longitudinal directions.