Performance of the Large Hadron Collider cleaning system during the squeeze: Simulations and measurements

• Main Authors: S. Tygier, R. B. Appleby, R. Bruce, D. Mirarchi, S. Redaelli, A. Valloni
• Format: Article
• Language: English
• Published: American Physical Society 2019-02-01
• Series: Physical Review Accelerators and Beams
• Online Access: http://doi.org/10.1103/PhysRevAccelBeams.22.023001

The Large Hadron Collider (LHC) at CERN is a 7 TeV proton synchrotron, with a design stored energy of 362 MJ per beam. The high-luminosity (HL-LHC) upgrade will increase this to 675 MJ per beam. In order to protect the superconducting magnets and other sensitive equipment from quenches and damage due to beam loss, a multilevel collimation system is needed. Detailed simulations are required to understand where particles scattered by the collimators are lost around the ring in a range of machine configurations. merlin++ is a simulation framework that has been extended to include detailed scattering physics, in order to predict local particle loss rates around the LHC ring. We compare merlin++ simulations of losses during the squeeze (the dynamic reduction of the β function at the interaction points before the beams are put into collision) with loss maps recorded during beam squeezes for run 1 and 2 configurations. The squeeze is particularly important, as both collimator positions and quadrupole magnet currents are changed. We can then predict, using merlin++, the expected losses for the HL-LHC to ensure adequate protection of the machine.