The light at the end of the tunnel gets brighter

With the LHC restart just a few months away, the future of the accelerator is as hot a topic as ever. In June, in the framework of the Medium-Term Plan, the CERN Council endorsed the construction of the LHC's successor, the High-Luminosity LHC (HL-LHC), which is set to take over from 2025 onwards.

 

Group photo at the HiLumi LHC/LARP Annual Meeting, 2013.

“This marks an important stage in the approval process of the HL-LHC,” says project coordinator Lucio Rossi. “It all started back in 2010 when the project was launched. In 2011, we obtained a European Commission grant for the conceptual design study under the Seventh Framework Programme (FP7) and, in 2013, the CERN Council identified the project as a priority at its special session dedicated to the European Strategy for Particle Physics. Finally, the Council this year confirmed the priority status of the HL-LHC project in the CERN scientific and financial programme by approving the Medium-Term Plan for the years 2014 to 2019. In so doing, it also took note of the total cost of the project up to 2025, which was provided for information in the MTP. That’s all very positive and enables CERN and its partners to prepare a long-term plan for developing the technologies and implementing the project.”

The HL-LHC project is being conducted by an international collaboration comprising CERN and many European, American and Japanese laboratories. Its aim is to increase the LHC's nominal luminosity – in other words, its ability to produce useful collisions – by a factor of 5 to 10 (peak luminosity by 5 and integrated luminosity by 10). This would allow an increase in the statistics produced for the Higgs boson* and other new particles, which would facilitate their analysis. Of course, the LHC accelerator chain will have to be upgraded (LIU project) in parallel as well as the detectors of the ATLAS, CMS, ALICE and LHCb experiments, on the same time scale as the accelerator’s upgrade.

Only 1.2 km of the existing accelerator will need to be replaced (mainly at Points 1 and 5) in order to turn the LHC into the HL-LHC. The new hardware (see box), which is based on innovative technologies that are mostly still under development, will be installed in the tunnel during the third long shutdown (LS3), starting in 2022. Thus rejuvenated, the LHC will have seen its useful lifetime extended by another ten years or so, until around 2035.

State-of-the-art technology

Short magnets of the new Inner Triplet Quadrupole (SQXF) made with advanced superconductor Nb3Sn. These magnets are currently under construction at CERN by the TE-MSC group.

Four components that are crucial to the future HL-LHC are currently being developed by CERN and its partners:

  • new niobium-tin (Nb3Sn) superconducting magnets: these quadrupoles (inner triplets), developed by a collaboration comprising CERN and US-LARP (US LHC Accelerator Research Program), will be able to reach more than 12 tesla (compared with 8 tesla for today’s LHC). The collaboration is also developing 11-tesla dipoles (the LHC magnets are limited to 8.3) to house the LHC's new arc collimation system;
  • new radiofrequency cavities: “crab cavities”, based on a technology never used before in a proton accelerator, are currently under development at CERN, in partnership with US-LARP and a UK collaboration comprising the University of Lancaster, the Science & Technology Facilities Council (STFC) and the Cockcroft Institute;
  • a new generation of collimators developed by CERN together with numerous European partners including the University of Manchester, London’s Royal Holloway University, the University of Huddersfield (UK) and the Spanish National Research Council (CSIC) in Valencia;
  • new magnesium-diboride–based (MgB2) superconducting cables capable of transporting electrical currents of 20 to 150 kA. These cables will make it possible to move the power converters currently located in the LHC tunnel to the surface, thereby greatly facilitating technical operations. They are being developed by CERN, the University of Southampton, INFN and a Genoa-based company, Columbus.

 

All these components, based on new superconducting technologies, will play a decisive role in the future of experimental particle physics as they will also be used in accelerators beyond the HL-LHC.

 

* More information on the research prospects of the ATLAS and CMS experiments at the HL-LHC is available in the proceedings of the 37th International Conference on High-Energy Physics (ICHEP): here for ATLAS, and here for CMS.

by Anaïs Schaeffer