A Movement Control System for Roman Pots at the LHC

This paper describes the movement control system for detector positioning based on the Roman Pot design used by the ATLAS-ALFA and TOTEM experiments at the LHC. A key system requirement is that LHC machine protection rules are obeyed: the position is surveyed every 20ms with an accuracy of 15Πm. If the detectors move too close to the beam (outside limits set by LHC Operators) the LHC interlock system is triggered to dump the beam. LHC Operators in the CERN Control Centre (CCC) drive the system via an HMI provided by a custom built Java application which uses Common Middleware (CMW) to interact with lower level components. Lowlevel motorization control is executed using National Instruments PXI devices. The DIM protocol provides the software interface to the PXI layer. A FESA gateway server provides a communication bridge between CMW and DIM. A cut down laboratory version of the system was built to provide a platform for verifying the integrity of the full chain, with respect to user and machine protection requirements, and validating new functionality before deploying to the LHC. The paper contains a detailed system description, test bench results and foreseen system improvements.