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Abstract:
At CERN’s Large Hadron Collider (LHC), proton and heavy-ion beams are accelerated to multi-TeV energies to be collided for the needs of the scientific community around the world. The total stored beam energy of tens to hundreds of MJ creates potential threats to the hard- ware around the collider in case of uncontrolled beam loss. Energy deposited by lost particles may damage impacted elements or cause the LHC magnets to lose their superconducting state, creating unnecessary downtime and decreasing physics production efficiency. To protect the machine a multi-stage collimation system was installed, designed primarily for proton operation but to be used also for heavy ions. However, with the upgrades for High-Luminosity LHC (HL-LHC), the total stored beam energy is to increase from 13 MJ to around 20 MJ. This demands an upgrade also from the collimation side to safely intercept higher beam losses that are to be expected due to higher intensity. Because of the fragmentation of heavy ions inside the collimators, which causes a significant leakage out of the collimators of particles with a charge-to-mass ratio that is different from the main beam, the collimation for heavy ions is more challenging than for protons. Hence, based on the studies performed in the past, it was decided to introduce a new collimation method with a potential for increased performance, called crystal collimation, in the operational baseline, already in 2023, when also the beams from the injectors with higher intensity became available.
The imminence of ion operations with crystal collimation presses for a more thorough under- standing of this novel method applied on heavy ions. For this reason, this thesis describes a complete simulation framework that has been built for ion crystal collimation. This tool allows a better understanding of the characteristics of crystal collimation for ions, probe for collima- tion optimizations, and perform predictive analysis for future collimation configurations. The simulation framework is based on the existing SixTrack-FLUKA coupling.
This thesis presents the construction of the simulation framework, the benchmark with old and new data, detailed simulation studies of the LHC collimation performance in various configurations, including the one of the first heavy-ion physics run with crystal collimation in 2023, and other alternative setups.
Rongrong Cai