ANALYSIS AND DESIGN OF THE ACTUATION SYSTEM FOR THE LHC COLLIMATORS (PHASE I)

In order to cope with the highly destructive particle beam of the LHC, the cleaning and collimation system must fulfill very severe requirements. The actuation system of the LHC Collimators is a key element to meet the specifications, particularly in terms of precision and reliability. Each collimator jaw has to be moved with a very high accuracy to place the active surface at the required position with respect to the proton beam; at the same time the system must be adjustable and flexible to adapt to the uncertainties and variations in the beam tuning. In this note the general design of the actuation system for the various collimator designs is presented and particular emphasis is given to the analysis of the torque which the stepper motors must provide to move the jaws in and back and to the dynamical behaviour of the system in the event of malfunctioning when auto-retraction of the jaws is required. In the appendix, details are given on the estimated performances of the actuation system for different collimator types and orientations.