Present status and future prospect on the initial realignment at the kekb injector linac

The initial realignment of beam lines is in progress at the KEKB injector linac; the realignment was necessitated by the Great East Japan Earthquake of March 2011 and is a requirement for the Super KEK B-factory project (SuperKEKB). Two alignment methods are applied to the initial realignment. One is a laser-based alignment technique applied to the two long straight sections. By using this technique, the transverse displacements of the accelerator girder units along the two long straight sections have been independently aligned with respect to two different laser axes. The other technique involves the use of a conventional laser tracker, and it is applied to the alignment of the components (accelerating structures and magnets) installed on the girder units and in the 180 arc section. A series of measurements provide an accurate view of the high-precision alignment of the linac beam line using the two alignment techniques. Regarding the component alignment, target bases for the accelerator structures and quadruple magnets have been newly fabricated and mounted for measuring the laser-tracker-based alignment. The girder units have been improved to increase their earthquake resistance by mounting a new support table for restricting their displacements in both the transverse and axial directions. For the alignment of the 180 arc section, refinement has been performed to connect the arc smoothly with the two straight sections. We have observed a non-negligible long-term drift of the tunnel floor along with a daily range of dynamical displacements due to tidal motion. We are now preparing a remote-controlled measurement system of the floor level to investigate the cause of such dynamical motion. This report contains a detailed description of the present status and future prospect of the initial realignment at the KEKB injector linac.