Effect of Quench Heater Discharges on the Circulating Beam in the Large Hadron Collider

The Large Hadron Collider (LHC) is a particle accelerator that uses superconducting dipole magnets to guide proton or heavy ion beams along their circular path. To protect these magnets from overheating in a small spot in case of a quench, the transition from superconducting to normal conducting state, the magnet coils are equipped with a protection device called quench heaters. However, these heaters produce an undesired horizontal dipole field to which the beam can be exposed under certain circumstances, displacing it from its nominal path. In the LHC, this is not a critical failure. But with the upgrade to the High Luminosity LHC (HL-LHC) and without counter- measures, quench heater induced fields could lead to beam displacements reaching the physical aperture, potentially causing damage. As the beam moves inside a beam screen, a tube with a co-laminated copper layer, it is partly shielded from the external quench heater field due to the formation of eddy currents. In this thesis, we reconstruct the field inside the beam screen using beam position measurements and compare the resulting field rise times and levels to values obtained by various theoretical approaches. We find that the measured field levels agree within 10 % with the predictions. With respect to the rise times, we find that the external field rise is smeared out in both measurements and simulations, with four different models giving consistent results. However, the models predict a stronger shielding than observed in the measurements. Depending on the case, the models predict time constants that are about 2 to 5 times larger than in the measurements. As all the studied approaches are based on 2D models, 3D-effects are proposed as a possible explanation for this discrepancy.