Collimation dependent beam lifetime and loss rates in the LHC

Abstract

The four primary collimators in each LHC beam define the smallest aperture. Particles with high betatron amplitudes or momentum offsets will therefore hit first a primary collimator. The instantaneous particle loss rate at primary collimators measured by precise beam loss monitors (BLM) is an important measure for the global lifetime of the beams and a major ingredient to identify collimation induced performance limitations in the LHC. These loss rates have been measured during a number of LHC fills, featuring both "good" fills with high luminosity and "bad" fills with beam instabilities. The beam lifetime at the collimators was then calculated from these data for different cases. The results are presented and interpreted within this paper.