Please cite this article in press as: Leão RJ, et al. Magnet alignment on a common girder: Development of a length artefact for measurement accuracy improvement. Precis Eng (2017), http://dx.doi.org/10.1016/j.precisioneng.2017.04.013 ARTICLE IN PRESS G Model PRE-6565; No. of Pages 10 Precision Engineering xxx (2017) xxx–xxx Contents lists available at ScienceDirect Precision Engineering jo ur nal ho me p age: www.elsevier.com/locate/precision Magnet alignment on a common girder: Development of a length artefact for measurement accuracy improvement Rodrigo J. Leão a,c , Crhistian R. Baldo b,∗ , Maria L.C.C. Reis c , Jorge L.A. Trabanco d , Flavio Rodrigues a , Regis T. Neuenschwander a a Brazilian Synchrotron Light Laboratory – LNLS, Rua Giuseppe Máximo Scolfaro, 10000, Campinas, SP, CEP 13083-100, Brazil b Federal University of ABC – UFABC, Av. dos Estados, 5001, Santo André, SP, CEP 09210-580, Brazil c Aeronautics Institute of Technology – ITA, Prac ¸ a Marechal Eduardo Gomes, 50, São José dos Campos, SP, CEP 12228-900, Brazil d University of Campinas – UNICAMP, Cidade Universitária Zeferino Vaz, Campinas, SP, CEP 13083-970, Brazil a r t i c l e i n f o Article history: Received 12 December 2016 Received in revised form 22 March 2017 Accepted 19 April 2017 Available online xxx Keywords: Synchrotron light source Magnet-to-magnet alignment Coordinate measuring systems Optical probing sensor Multipurpose geometrical artefact a b s t r a c t The tolerances for the alignment of the magnets on the girders of the proposed particle accelerator of the Brazilian Synchrotron Light Laboratory (LNLS), Sirius, are as small as 40 m for translations and 0.3 mrad for rotations. The functional axis of the magnets is measured by the vibrating wire technique, which employs conductive wires of diameters of approx. 0.1 mm. Since the alignment has to be per- formed targeting these magnetic axes, rather than their geometric centrelines, non-contact measuring sensors mounted on a coordinate measuring machine have been chosen to measure the relative deviations between magnets. To better the measurement accuracy for that specific measuring task, to allow interim checks on multiple coordinate measuring systems, and to provide effective traceability to the SI unit of length, a multipurpose geometrical artefact has been devised. The reasoning behind this development and the first measurement results are described in this paper. © 2017 Elsevier Inc. All rights reserved. 1. Introduction In December 2014, the construction of Sirius, the new particle accelerator at the Brazilian Synchrotron Light Laboratory (LNLS) officially began, on the campus of the Brazilian Centre for Research in Energy and Materials (CNPEM). It is to be the brightest light source of its kind, comparable only to MAX IV, in Sweden [1]. It is also considered the greatest scientific project in Brazil, raising competitiveness in fields of research such as materials science, medicine, biology and chemistry. The matter of aligning magnets on a common girder is of prime relevance for the operation of particle accelerators. The perfor- mance of these complex machines relies on very stable trajectories of charged particles, which travel near the speed of light. The key components of particle accelerators are the magnets that maintain the beam at a desirable path. For them to work properly, however, their orientation and position must be kept to a high level of accu- racy and precision. In fact, the tolerances for the alignment of the ∗ Corresponding author. E-mail address: crhistian.baldo@ufabc.edu.br (C.R. Baldo). magnets (quadrupoles and sextupoles) on the girders of the com- ing Sirius are as small as 40 m for translations and 0.3 mrad for rotations. The magnets are approximately 400 mm wide, and the overall dimensions of the accelerator tunnel can be seen in Fig. 1. The alignment of a particle accelerator involves putting its components into a certain position and orientation in the tridi- mensional space. The task is to perform the alignment by looking at the magnetic axis that defines each component. The magnetic axis of a magnet may not coincide perfectly with the geometric axis because of a number of factors, from dimensional and geometrical deviations to inhomogeneities of the core ferromagnetic material [2–4]. The alignment of the particle accelerator components may be understood as a two-phase process, which first comprises of the magnet-to-magnet on a common girder and then the girder-to- girder alignments (see Fig. 2). The determination of the magnetic axis of accelerator magnets is beyond the scope of this paper. However, it is necessary to men- tion that the vibrating wire technique [5] will be employed to align the magnets of the Sirius accelerator. For this technique, the geo- metrical survey is normally carried out by indirectly finding the position of the wire through wire position sensors with fiducial ref- erences, which are later related to the magnet fiducial references http://dx.doi.org/10.1016/j.precisioneng.2017.04.013 0141-6359/© 2017 Elsevier Inc. All rights reserved.