Implications of the LHCb Upgrade II on the LHC

Abstract

The Upgrade II of the LHCb (Large Hadron Collider beauty) experiment is proposed for Long Shutdown (LS) 4, aiming to operate at 1.5e34cm^(-2)s^(-1) and reaching an integrated luminosity slightly less than 400fb^(-1) by the end of the High Luminosity LHC (HL-LHC) era. This increase of luminosity is going to enlarge the data sample at LHCb providing an unprecedented opportunity for heavy flavour physics measurements. During LS2, a first upgrade of LHCb (Upgrade I) has already been realised allowing operations at 2e33cm^(-2)s^(-1), five times more than the value reached during Run2. The mentioned luminosity increase will have an impact not only on the experimental apparatus but also on the functional elements of the LHC, magnets, cryogenics and electronic equipment placed in the Insertion Region 8 (IR8). The LHCb experiment was conceived to operate at a lower luminosity than the two LHC general purpose experiments, ATLAS and CMS. This implied minor requirements for protection of the LHC elements from the collision debris and therefore a different layout around the LHCb Interaction Point (IP8). However, with the HL-LHC era and the LHCb upgrades, the predicted radiation levels will be comparable with those achieved by ATLAS and CMS during Run2, requiring a systematic study of the current layout and the conceivable enforcement of a variety of protection measures in IR8 from the collision debris. Monte Carlo simulations are a powerful tool to predict the interaction between particle showers and accelerator elements, especially in case of future scenarios. In this regard, a FLUKA model of the experimental area in the LHCb region and of the LHC tunnel has been set up and benchmarked with experimental data to evaluate radiation levels and particle fluences due to proton collisions. Firstly, annual radiation levels after the Upgrade II of LHCb will increase by a factor of 5 with respect to the values after the Upgrade I, implying the need to shield the electronics placed in the experimental areas, to mitigate the single event effect (SEE) risk which may imply recurring downtime of the LHC and to preserve the electronics performance. Furthermore, the impact of radiation on the LHC magnets (i.e. final focusing quadrupoles, separation and recombination dipole, dispersion suppressor elements) was studied in terms of transient effects and damage risk. In conclusion, the luminosity target proposed for Upgrade II can be sustained with protection systems for magnets and electronics, requiring to review the layout of IR8 to ensure safe operation of the LHC magnets.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robert Appleby (Supervisor) & Christopher Parkes (Supervisor)