Automatisation of the SPS ElectroStatic Septa Alignment

An electrostatic septum (ZS) composed of 5 separate tanks is used to slow-extract the 400GeV/c proton beam resonantly on the third-integer resonance from the CERN Super Proton Synchrotron (SPS). The septa are all mounted on a single support structure that can move the ensemble coherently. In addition, the internal anode and cathode of each tank can be moved independently. The septum is aligned to the beam by measuring and minimising the induced beam loss signals in the extraction region following an alignment procedure that is usually carried out at the beginning of each year. The large number of positional degrees of freedom complicates the procedure and until recently each tank was aligned one after the other semi-manually, typically requiring 8 h. It is not uncommon that the septum has to be re-aligned later in the run taking time away from the physics programme. To tackle this issue, a simplified beam dynamics and scattering simulation routine was developed to permit error studies with a large number of seeds to be carried out in a reasonable computation time. In this contribution, the simulation model will be described before the results of its exploitation to understand the efficacy of alignment procedures based on different optimisation algorithms is discussed and compared to the present operational procedure. The effort culminated with the implementation of an automated alignment procedure based on a Powell optimisation algorithm that reduced the time needed to align the septum by over an order of magnitude.