Regina Kwee-Hinzmann

Chapter 5: Collimation System

1UMAN, The University of Manchester and the Cockcroft Institute, Warrington, UK 2UHUD, University of Huddersfield, Huddersfield, UK 3CERN, Accelerator & Technology Sector, Geneva, Switzerland 4IFIC, Instituto de Fisica Corpuscular, Valencia, Spain 5URHL, Royal Holloway, London, UK 6IFIC, Instituto de Fısica Corpuscular, Valencia, Spain (now ESS European Spallation Source, Lund, Sweden 7SLAC National Accelerator Laboratory, Menlo Park, USA 8FNAL, Fermi National Accelerator Laboratory, Batavia, USA

Validation of Off-momentum Cleaning Performance of the LHC Collimation System

The LHC collimation system is designed to provide effective cleaning against losses coming from off-momentum particles, either due to un-captured beam or to an unexpected RF frequency change. For this reason the LHC is equipped with a hierarchy of collimators in IR3: primary, secondary and absorber collimators. After every collimator alignment or change of machine configuration, the off-momentum cleaning efficiency is validated with loss maps at low intensity. We describe here the improved technique used in 2015 to generate such loss maps without completely dumping the beam into the collimators. The achieved performance of the collimation system for momentum cleaning is reviewed.

LHC Collimation and Energy Deposition Studies Using Beam Delivery Simulation (BDSIM)

Beam Delivery Simulation (BDSIM) is a program that uses a suite of high energy physics software including Geant4, CLHEP and ROOT, that seamlessly tracks particles through accelerators and detectors utilising the full range of particles and physics processes from Geant4. A comparison of the collimator cleaning efficiency and energy deposition throughout the full length of the Large Hadron Collider (LHC) with the established SixTrack simulations of the CERN collimation group is presented. The propagation of the full hadronic showers from collimators provides unparalleled detail in energy deposition maps and these are compared with the data from beam loss monitors that measure radiation outside the magnet body.