Automatic angular alignment of LHC collimators

The Large Hadron Collider (LHC) is equipped with a complex collimation system to protect sensitive equipment from unavoidable beam losses. Collimators are positioned close to the beam using an alignment procedure. Until now they have always been aligned assuming no tilt between the collimator and the beam, however, tank misalignments or beam envelope angles at large-divergence locations could introduce a tilt limiting the collimation performance. This paper describes three different algorithms to automatically align a chosen collimator at various angles. The implementation was tested with and without beam at the SPS and the LHC. No human intervention was required and the three algorithms converged to the same optimal tilt angle.