BEAM ORBIT STABILIZATION AT THE SPring-8 STORAGE RING

The SPring-8 storage ring is a third generation X-ray source providing brilliant photon beams. Continuous performance improvement realizes small horizontal and vertical beam sizes reaching to respectively 280μm and 4μm in rms at the source point of each standard insertion device (ID) [1]. Especially in a vertical plane, small orbit variation enlarges the vertical beam size and an orbit drift also changes intensity of monochromatized X-ray beam at an experimental hutch. Beam orbit stability is thus one of the most important subjects for the best use of an advantage of a small source size. However, the sufficient orbit stability is not easily achieved, because the beam orbit variation is generated by a complicated system that the various kinds of perturbation sources are interrelated and widely distributed over the ring. This complex environment prevents us from finding out the main perturbation sources easily and also limits the effectiveness of countermeasures. To overcome this, it is critically important that equipment, utility systems, beam controls, and a building structure, such all machine subsystems are re-investigated, improved and re-integrated from the unified viewpoint of orbit stability. In this context, a project on beam orbit stabilization in the SPring-8 storage ring started aiming at sub-micron stability at the beginning of year 2001. Experts of all machine subsystems were gathered to form the project team for systematic and unilateral investigation of the problem. During the last two years, we have successfully reduced the orbit variations in a frequency range from DC to a hundred Hz and reached to a point where the stability of sub-micron level comes into our landscape. In this paper, we review our activities and show present results on the orbit stabilization focusing on the latest topics.