High-Luminosity LHC moves to the next phase

This week saw several meetings vital for the medium-term future of CERN. 

From Monday to Wednesday, the Resource Review Board, RRB, that oversees resource allocation in the LHC experiments, had a series of meetings. Thursday then saw the close-out meeting for the Hi-Lumi LHC design study, which was partially funded by the European Commission. These meetings focused on the High Luminosity upgrade for the LHC, which responds to the top priority of the European Strategy for Particle Physics adopted by the CERN Council in 2013. This upgrade will transform the LHC into a facility for precision studies, the logical next step for the high-energy frontier of particle physics.

It is a challenging upgrade, both for the LHC and the detectors. The LHC is already the highest luminosity hadron collider ever constructed, generating up to a billion collisions per second at the heart of the detectors. The High Luminosity upgrade will see that number rise by a factor of five from 2025.

For the detectors, significant upgrades are necessary to maintain detector performance at higher luminosity. In a challenging financial environment, detector upgrades must be subject to strict financial management in order to exploit the physics potential of high luminosity to the maximum while minimising the financial outlay.

At this week’s RRB, ATLAS and CMS presented their Technical Proposals, supplemented with scoping documents containing the impact on the physics reach as a function of three funding scenarios, together with a preliminary money matrix containing indicative planning figures from participating institutes. These documents will be subject to continuous scrutiny by the Upgrade Cost Group, UCG, whose evaluation of costs and schedules will complement the scientific analysis of the LHC Experiments Committee, LHCC. The full process will take us up to 2025, marking the conclusion of the LHC’s initial discovery phase.

In parallel, there is much to be done to prepare the LHC itself for high-luminosity running. The Hi-Lumi LHC design study was the R&D phase of this process. The close-out meeting on Thursday therefore signalled the end of a hugely complex and collaborative design phase, and the beginning of prototyping and industrialisation. Over the coming months and years, new magnets, many under development by partner labs, will be refined and installed, along with innovative structures known as crab cavities that will manipulate the beams to ensure maximum collision rates.

The High-Luminosity LHC upgrade will mark a transition from the LHC’s discovery phase to in-depth exploration of new physics. This is in many ways analogous to the move from the discovery of W and Z particles with the SPS collider in the 80s to in-depth exploration with LEP through the 90s. What makes the LHC different is that the High Luminosity upgrade will allow us to cover both phases with a single, remarkable, machine.

Rolf Heuer