Aurelien Van Boxel

Criticality of spurious quench heaters discharge at the High-Luminosity LHC

Abstract

In the constant aim to refine the experiments and raise the number of collisions, the present CERN’s Large Hadron Collider will be upgraded to the new High Luminosity LHC, by increasing the luminosity and multiplying by a factor two the energy stored in each beam. Hence, this upgrade can lead to new issues in the machine protection system. This project focuses on the study of spurious quench heaters discharge in the separation and recombination dipoles placed at the interaction point 5 (IP5), where sits the detector CMS, and their numerical simulation. Indeed, if this fast failure occurs in the dipoles without mitigation, the machine could be severely damaged. The failures considered as fast are failures that can lead to beam losses within 10 ms from their onset. More precisely, the quench heaters are systems used to avoid uncontrolled quenching phenomena (loss of superconductivity), in the form of resistive strips, but if they suffer of failures, the high energy of the beam can destroy the magnet. First and foremost, the theoretical background is introduced, and some LHC design aspects are reviewed, including the different types of magnets, the quench heaters and the crossing angle. To simulate numerically the fast failures in quench heaters, the FailSim framework is used, after being described as well as the simulation pattern. As the quench heaters, they are modelled using CERN’s standard program MAD-X. Thanks to this modelling, the results are generated. Firstly, the amplitude function is showed in the entire machine and around IP5. Its shape conforms to the predicted one. Secondly, different plots of orbit excursion are presented. They provide the key result of the study. Indeed, according to what was expected, the orbit excursion is oscillating and the dipole D1 is the most critical, due to its magnetic configuration where two circuits goes across the magnet, resulting in a partially protection of the magnet quadrants. Moreover, that is D1 (MBXF.4r5) that is responsible of the largest orbit excursion. In addition to that, the most problematic element is also determined, and that is the MCBXFAH.3r5 corrector. After this analysis mainly based on the FailSim framework, it is clear that special attention must be given to the dipole D1 in terms of machine protection, and a future application is to study the beam losses of spurious quench heaters discharge.