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

TL;DR

This paper evaluates the LHC's cleaning system performance during the squeeze phase using simulations and measurements, aiming to predict losses for future high-luminosity upgrades.

Contribution

It extends the Merlin++ simulation framework with detailed scattering physics to accurately predict particle losses during the LHC squeeze.

Findings

Simulations match measured loss maps during the squeeze.

Predictions for HL-LHC losses are feasible with the extended model.

The study improves understanding of beam loss management during dynamic machine configurations.

Abstract

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 multi-level 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 \beta-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.