DOE OSTI2013
The required positioning tolerances are an essential part of the survey and alignment design. The following tables show the requirement of storage ring. Table 1 provides the required global tolerances, while Table 2 outlines the relative tolerances for the NSLS-II girder-to-girder positioning. These tolerances dictate the instruments and methods necessary to obtain the positioning goals. The global tolerance is a little bit relaxed, but the ± 0.10 mm positioning requirement of adjacent girders is rather strict if the larger dimension and probable foundation settlement is considered. control network. Therefore, whether the goals can be obtained is mainly dependent on the performance of control network. The shape of control network defines the global alignment accuracy, while the relative position relationships of monuments determine the relative positioning accuracy between girders. When deciding the strategy of survey and alignment techniques, the instrumentation and approach of light sources have been built and are still in construction are investigated. State-of-the art equipment and methods will be employed. NSLS-II covers an area of about one-eighth of a square kilometer with a radius of ~126 m and a circumference of ~792 m. Depending on the size of the system to be constructed, primary and secondary control networks are required to achieve these tolerances. Primary control network will provide global control for different tunnels, and it should possess a relative point accuracy of better than ± 3 mm for all the storage ring monuments. Secondary control network will direct the alignment of girders in tunnel with the ability to ensure the final ± 0.10 mm positioning accuracy. The experiences from accomplished light source indicate that: for a dimension like NSLS2, primary control network can obtain a point accuracy of better than ± 1 mm easily, while secondary control network can obtain a relative point accuracy of ± 0.08 mm. With this expectation, the tolerance can be achieved for both the global and relative situation. Take the relative positioning requirement as an example, with 2 control network error of ± 0.08 mm, instrument tie-in error of ± 0.04 mm, and residual error of ± 0.04 mm, according to error propagation formula, the final alignment error should be better than ± 0.1 mm. Correspondingly, if a better control network accuracy can be achieved, the requirement for the residuals can be looser. The further alignment accuracy improvement will be realized by a smoothing process to assure the better position relationship between adjacent girders. The following simulation will perform error analysis to evaluate the estimated accuracy of NSLS II control network.