Simulation of ion beam losses in LHC magnets

At the particle physics laboratory CERN, the largest accelerator ever, the Large Hadron Collider (LHC), is under construction. In the LHC ultra relativistic particles, mainly protons but also lead ions, will be brought into collision. One problem that arises in the operation is that colliding ion beams in the machine have a very large cross section for electromagnetic interactions, in particular Bound Free Pair Production (BFPP). An electron-positron pair is created by the electromagnetic field between two colliding particles and the electron is created in a bound state of one of the ions. Because of this reaction the ion changes its charge and therefore leaves the wanted trajectory and crashes in a superconducting magnet, depositing heat. The impact of the wrongly charged ions on the inside of the vacuum pipe was simulated with the simulation program FLUKA. It was concluded that it is not likely that enough heat is deposited in the coils of the superconducting magnet to induce a quench, although some uncertainties exist. A necessary safety measure that can protect against quenches due to BFPP or other beam losses is the beam loss monitor (BLM) system, which was initially designed for the proton beam. In this thesis, the ratio between the signal on the BLM and the heat deposition in the coils of the superconducting magnet was simulated for both lead ions and protons, and it was concluded that this ratio is approximately the same. This means that the same thresholds in the beam abort system can be used for both particle types, provided that the losses occur at the same places. Finally the response of the BLM system at the RHIC accelerator in Brookhaven to copper ions undergoing BFPP was simulated and compared with experimental data. Unfortunately the correspondence was not as good as was hoped. Several possible error sources that could cause this discrepancy were identified.