Using ALFA Detectors for the LHC Beam Background Measurements

This paper presents background measurements during elastic data taking in 2018 with $\beta^\ast = 100$ m at injection energy using ALFA detectors in the ATLAS experiment. Such special runs require specific collimation scheme which allows to reduce beam induced background. Hence, complex preparation including simulations and tests had to be performed. This document covers results of tests with different collimation schemes and background observation during final data taking. One of the runs was devoted to test a new type of collimators based on crystal channelling effect that were used during physics data taking for the first time at the LHC.