Feasibility study of multipoint based laser alignment system for CLIC

CLIC (Compact LInear Collider) is a study for a future electron-positron collider that would allow physicists to explore a new energy region beyond the capabilities oftoday’s particle accelerators. Alignment is one of the major challenges within the CLIC study in order to achieve the high requirement of a multi-TeV center of mass colliding beam energy range (nominal 3 TeV). To reach this energy in a realistic and cost efficient scenario all accelerator components have to be aligned with an accuracy of 10 μm over a sliding window of 200 m. The demand for a straight line reference is so far based on stretched wires coupled with Wire Positioning Sensors (WPS). These solutions are currently further developed inorder to reduce the drawbacks which are mainly given by their costs and difficult implementation. However, it should be validated through inter-comparison with a solution ideally based on a different physical principle. Therefore, a new metrological approach is proposed using a laser beam as straight line reference. Optical shutters paired with CCD (Charge-Coupled Device) based cameras are proposed to visualise the laser beam. This new technology is currently studied and developed in an optical laboratory. The paper presents the alignment principle, the theoretical background, and introduces related key-parameters. First experiments were performed based on a 2 m long setup in order to validate the principle. Low cost components were implemented for these tests which are however showing encouraging results. The conclusion allows a first approximation of achievable measurement precision and repeatability. In addition these experiments are building up a basis for a first extrapolation of the accuracy over a longer distance.