Sirius pre-alignment results

Sirius is a 4th generation synchrotron light source under final installation and beginning of commissioning phase in Brazil, with a bare emittance of 250 picometer rad. In order to fulfil stability requirements (maximum magnets displacement of 6 nm caused by vibration) imposed to achieve expected performance, the mechanical assembly of supporting structures and magnets were designed without adjustment mechanisms. Yet, the misalignment errors of the magnets are the dominating source of dynamical aperture reduction, leading to a maximum permissible deviation of 40 micrometers between adjacent magnets. To this end, dimensional engineering was applied to conceive an alignment concept for magnets on a same girder based solely on the geometric characteristics of the parts. For the large volume positioning of girders in the storage ring tunnel, the applied methodology followed a strategy optimized to reduce measurement uncertainty, as described in the literature. This paper will present the complete measurement process that led to the pre-alignment of Sirius, from the deployment and survey of reference networks to planning future fine alignment of the machine. To express a consistent and unequivocal alignment result and assess the alignment quality considering the measurement uncertainty, an innovative metric described previously was employed. This work will show that the positioning of girders satisfies the requirement of 80 micrometer. Also, the devices and mechanisms used for assembling will be detailed. Inspection of full girder set performed on a Coordinate measuring machine shows a maximum deviation of 30 micrometers for any pair of magnets on a common girder.