Experimental verification for a collimator with in-jaw beam position monitors

Abstract

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the

two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility

and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully

tested with a mock-up collimator in the CERN-SPS. Extensive beam experiments allowed to determine the achievable

accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are

discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC.