Long shutdown 2 LHC smoothing status and data analysis

During the two-year Long Shut-Down 2 (LS2), triggered by the LHC Injectors Upgrade (LIU) project, the CERN surveyors took in charge the smoothing of the 27km com- ponents of the LHC to guarantee its best beam aperture and energy performance for the RUN3 between 2022 and 2026. During this large measurement campaign, the roll angle of the LHC components in the Long Straight Section (LSS) as well as their position in vertical and in horizontal direc- tions were measured by direct levelling and stretched wire methods. These initial data were computed by CERN homemade software to define and optimize the workload of the displacement sequence, in order to re-align all the cryo-magnets within a +/- 0.2 mm tolerance. This LS2 smoothing campaign at cold (> 80K) is the third one after the LHC installation (2008) and LS1 (2013- 2014). CERN has now collected an important source of data useful for the analysis of the LHC stability which will allow the survey team to predict the areas where future movements are going to take place. The paper gives an overview of the methodologies, tech- niques and software used for the smoothing, the realign- ment process and an analysis of the stability of the LHC tunnel based on the data collected during the three cam- paigns.