Vertical displacement of the storage ring floor due to building distortion in the Photon Factory

Abstract

The Light Source Building of the Photon Factory was found to distort so much as to induce the displacement of magnets in the storage ring. This resulted in drifting of the beam orbit. It was considered that the building was distorted by the variations of thermal stress, such as diurnal changes of the solar irradiation and atmospheric temperature. To reduce such thermal stress, the rooftop of the building was insulated with a layer of polyethylene foam. The building distortion was measured in terms of vertical floor displacements along the storage ring by using a hydrostatic level measuring system. Results of the measurement were compared with those of a model simulation based on the finite element method. Comparison between measured and simulated results showed good agreement before the insulation applied to the roof. After the insulation, the measured floor displacements reduced to about one half and were also comparable to the simulated results. A full description of the subject is given in T. Katsura, Ed., KEK Internal 90-32 (in Japanese) Jan. (1991).