Application of close-range photogrammetry to particle accelerator alignment

This paper presents the first time application of close-range photogrammetry to control net and components measurement in domestic particle accelerator facilities. A detailed measurement scheme is formulated to meet the narrow space of the tunnel, two kind of targets are designed (the hemisphere target and five plane faces target) and an idea is put forward to make the planar coded targets into a three dimensional group to satisfy the tunnel condition. Besides short baseline of a standard bar, long baseline based on laser tracker was also added for constraint. A measurement experiment was conducted in the 70 m long tunnel which is a part of RCS in CSNS, and the coordinates of the control points and the components are successfully obtained, the accuracy was 0.5 mm as compared with that of the laser tracker. This photogrammetric method has remarkably improved efficiency and achieved good result as expected.