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.
Highlights
The Large Hadron Collider (LHC) collimation system [1,2] is designed to protect the ring from normal beam losses caused by diffusion and scattering, as well as abnormal fast losses
The LHC collimation system is essential to protect the machine from beam losses during operation
We can use existing measurements to validate simulations, which can be used to make a prediction of the future performance for High-Luminosity Large Hadron Collider (HL-LHC)
Summary
The LHC collimation system [1,2] is designed to protect the ring from normal beam losses caused by diffusion and scattering, as well as abnormal fast losses. Before bringing the LHC beams into collision, they must first be ramped from the injection energy (450 GeV) to full energy (6.5 TeV in run 2) and the βà [the β function at the experiment interaction points (IPs)] reduced. This latter part of the operational cycle is called the squeeze. This gives us the confidence in Merlin++’s particle tracking and scattering models, in order to use it for making predictions of future configurations. This corresponds to a 0.2 h beam lifetime over 10 s [19,20], giving a total loss power of about 1 MW
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