Betatron squeeze optimisation at the Large Hadron Collider based on first year of operation data

In order to achieve the high luminosity expected from the Large Hadron Collider, the beta function at the interaction points must be minimised. As the aperture in the surroundings of the interaction points become smaller and smaller with decreasing beta function at the interaction point, the latter is kept higher during injection and energy ramp and reduced before the production of collision, by the means of the betatron squeeze. This operation as shown to be very critical in previous colliders, however, good performances were achieved early during the commissioning of the machine allowing to optimise this operation along the year. Firstly, a systematic fill by fill analysis of the beam parameters is performed in order to point out, understand and solve potential issues, allowing, in particular, to minimise the beam losses during the operation. Secondly, simulations of beam parameters based on the strength of the magnets extracted from the control system are introduced and validated with measurements. The simulations are then used to validate new sets of settings for the magnet that allow to perform an identical operation within a shorter duration. Based on this analysis, an optimised set of settings is proposed for operation in 2011.