New sensor and non-contact geometrical survey for the vibrating wire technique Renan Geraldes a , Rodrigo Junqueira Leão a, n , Geraldo Cernicchiaro b , Regis Terenzi Neuenschwander a , James Francisco Citadini a , Antônio Ricardo Droher Rodrigues a a Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil b Brazilian Center for Research in Physics (CBPF), Rio de Janeiro, RJ, Brazil article info Article history: Received 22 September 2015 Received in revised form 13 November 2015 Accepted 9 December 2015 Available online 21 December 2015 Keywords: Fiducialization Geometrical survey Magnetic bench Particle accelerator alignment Quadrupole Synchrotron light source abstract The tolerances for the alignment of the magnets in the girders of the next machine of the Brazilian Synchrotron Light Laboratory (LNLS), Sirius, are as small as 40 mm for translations and 0.2 mrad for rotations. Therefore, a novel approach to the well-known vibrating wire technique has been developed and tested for the precise fiducialization of magnets. The alignment bench consists of four commercial linear stages, a stretched wire, a commercial lock-in amplifier working with phase-locked loop (PLL), a coordinate measuring machine (CMM) and a vibration sensor for the wire. This novel sensor has been designed for a larger linear region of operation. For the mechanical metrology step of the fiducialization of quadrupoles an innovative technique, using the vision system of the CMM, is presented. While the work with pitch and yaw orientations is still ongoing with promising partial results, the system already presents an uncertainty level below 10 mm for translational alignment. & 2015 Elsevier B.V. All rights reserved. 1. Introduction In December 2014, the construction of Sirius, the new particle accelerator at the Brazilian Synchrotron Light Laboratory (LNLS) has officially begun, on the campus of the Brazilian Center for Research in Energy and Materials (CNPEM). It promises to be the brightest light source of its kind, comparable only to MAX IV, in Sweden. It is also considered the greatest scientific project in Brazil, raising competitiveness in fields of research such as mate- rials science, medicine, biology and chemistry. For the accelerator to perform as designed, however, the demands on engineering are extremely high. High precision in the alignment of the magnets is particularly important. The x and y RMS alignment requirements of quadrupoles and sextupoles in a girder has been specified to within 40 mm, while the rotational tolerances for pitch, yaw, and roll are of only 0.2 mrad [1]. The geometrical and magnetic axes of multipole magnets may differ by a few micrometers [2], due to fabrication processes, mounting repeatability and variations in material properties. Therefore, to perform an alignment using the physical body of the magnet, it is necessary to find its magnetic axis and correlate it to external fiducials. This process is known as the fiducialization of a magnet, which is in this paper (as in [2]) divided in two steps, namely: finding its magnetic axis using a magnetic survey tech- nique and relating the magnetic center axis to a frame in the magnet yoke using a geometrical survey technique. This second step is often divided in two steps, due to an indirect measurement of the magnetic axis position [3]. In any case, several techniques have been employed for both kinds of surveys [4,5]. As for the magnetic survey, the vibrating wire has been pro- posed in [6] as an evolution of other wire techniques, as the moving, the pulsed and the stretched wire techniques, with the particular advantage of precisely (and univocally) determining the magnetic axis of magnets [4,5]. Since then, it has been successfully implemented in the alignment and fiducialization of multipole magnets and solenoids [3,4], [6,7,8,9,10,11,12], as well as the characterization of insertion devices, such as superconducting wigglers and undulators [13,14,15]. Another technique that is often used for magnetic survey is the rotating coil. It is very powerful for multipole characterization of magnets [16] and can also be used to find the magnetic axis of a given magnet [2], although it is rather limited in the precise determination of the coil axis to a few tens of micrometers [4]. Nonetheless, this technique may conveniently support the vibrating wire in the fiducialization of the roll angle, to which the latter is essentially insensitive. Today the most used geometrical survey methods are portable coordinate measuring systems, like measuring arms and laser trackers, or fixed coordinate measuring machines [2,3,4,17]. Other techniques, like the use of traditional theodolites or laser Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A http://dx.doi.org/10.1016/j.nima.2015.12.016 0168-9002/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ55 19 3512 3135; fax: þ55 19 3512 1004. E-mail address: rodrigo.leao@lnls.br (R. Junqueira Leão). Nuclear Instruments and Methods in Physics Research A 811 (2016) 115–123