MAGNET SUPPORT AND ALIGNMENT

From theoretical design of the storage ring and injection system, we move to physical installation. The challenge facing the alignment team is to translate a theoretical storage ring layout designed in Cartesian space into a physical ring in geocentric space—to transform a list of theoretical coordinates into a physical system in which each component lies at its design location to within a specified tight tolerance. How to accomplish this transformation is the subject of this chapter. As alignment tolerances get ever tighter, the interplay of alignment with mechanical engineering becomes ever more important. In fact, accelerator alignment has advanced so far that mechanical uncertainties now exceed observational uncertainties. Of the mechanical issues bearing upon alignment, one of the most crucial is the magnet supports; these must provide both stability and a fineness of motion substantially exceeding the final alignment tolerances. This chapter therefore includes a section on mechanical support systems and their implications for alignment. This chapter covers three topics: mechanical schemes to support and align storage ring and injection system components; survey and alignment of those components; and ground motion. The first section addresses magnet supports (girders and individual magnet stands) and mechanical adjustment systems (shims, struts, and cross slides). The second section focuses on the alignment of synchrotrons, storage rings and injection lines, and examines the propagation of errors associated with these processes. The relationship of the lattice coordinate system to the selected layout coordinate system, and the subsequent computation of ideal component coordinates are described, followed by a broad overview of the sequence of alignment activities from the initial absolute positioning to the final smoothing. Emphasis is given to the relative alignment of components; in particular, to the importance of incorporating methods to remove residual systematic effects in surveying and alignment operations. The third section reviews ground motion issues, and describes measures for alleviating disturbances.