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Description
The Einstein Telescope (ET) is a proposed third-generation gravitational-wave observatory requiring an ultra-high vacuum infrastructure of approximately 120 km with stringent alignment tolerances. To validate key engineering and installation procedures, the Einstein Telescope pilot has been constructed at CERN as a reduced-scale demonstrator using full-size representative vacuum components arranged in a shortened configuration.
This paper presents the survey and alignment methodology developed for the pilot, including fiducialisation of beam tubes and end caps, establishment of a precision survey network, setting out of supports, pre-weld alignment, and final installation using laser tracker technology. Iterative adjustment procedures with real-time feedback were used to achieve alignment with respect to the nominal beamline.
The achieved alignment accuracy is reported, highlighting the effects of manufacturing tolerances, welding distortions, structural deformation, and support system limitations. Despite gravitational sag and fabrication-induced offsets, all components were positioned within the required tolerances of the pilot configuration.
Rather than demonstrating the feasibility of a specific measurement methodology for the full observatory, the study shows alignment achievable with the existing adjustment systems. At the same time, it highlights that construction of the full-scale Einstein Telescope will require more automated survey and alignment workflows to achieve the necessary efficiency, repeatability, and scalability for large-scale deployment.
