CERN Accelerating science

Article
Report number	CERN-ACC-2025-0003
Title	Shutter-type multi-point optical alignment using a Structured Laser Beam in vacuum
Author(s)	Niewiem, Witold Grzegorz (ETH, Zurich (main) ; CERN) ; Figura, Sebastian Antoni (CERN) ; Dusek, Martin (Liberec Tech. U. ; CERN) ; Mergelkuhl, Dirk (CERN) ; Gayde, Jean-Christophe (CERN) ; Wieser, Andreas (ETH, Zurich (main))
Publication	2025
Imprint	08 May 2025
Number of pages	19
In:	JINST 20 (2025) P07001
DOI	10.1088/1748-0221/20/07/P07001
Subject category	Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LHC
Free keywords	Detector alignment and calibration methods (lasers, sources, particle-beams); Accelerator ; Subsystems and Technologies
Abstract	This paper presents an alignment concept employing a Structured Laser Beam (SLB) for offset measurements over a 140 m distance. The prototype consists of an SLB generator and three measurement stations within a vacuum system. The Inner Core (IC) of the SLB establishes an optical axis that serves as a reference line. A comparative assessment is performed against a Wire Positioning System (WPS) and Hydrostatic Levelling System (HLS). Two independent measurements of the prototype show that it exhibits high relative precision, with a standard deviation of offset measurements below 20 μm. The acquisitions reveal that the prototype results are shifted relative to WPS-HLS measurements. This shift, observed in both transverse directions, can be attributed to the multi-stage fiducialisation process, which introduces additional uncertainty. This result can be improved by modifying the prototype design and the fiducialisation measurement method. The SLB-based prototype is a promising candidate for alignment applications in particle accelerators due to its high precision over long distances.
Copyright/License	publication: © 2025 The Author(s) (License: CC BY 4.0)

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