EU supports the LHC high-luminosity study

The design collision energy and luminosity of the LHC are already at record numbers, making the machine one of the most complex scientific instruments ever built. However, to extend its discovery potential even further, a major upgrade of the LHC will be required around 2020. This will increase its average luminosity by a factor of 5 to 10 beyond its design value. Fifteen worldwide institutions and the European Union are supporting the initial design phase of the project through the HiLumi LHC programme, whose kick-off meeting will take place on 16-18 November.


The CERN team that has successfully built and tested the Short Magnet Coil – a small 40 cm long magnet capable of producing a 12.5 T magnetic field.

The upgrade of the LHC will require about 10 years of design, construction and implementation. The new machine configuration will be called “High Luminosity LHC” (HL-LHC). The similarly named “HiLumi LHC” is the EU programme that supports part of the design phase of HL-LHC. “Formally, HL-LHC is a new run of the LHC,” says Lucio Rossi, Deputy Head of the Technology (TE) Department and HL-LHC project Co-ordinator. “The upgrade will include some key new elements that will increase the LHC's integrated luminosity by up to a factor of 10, enabling us to reach the goal of 3000 fb-1  (per collision point) set by ATLAS and CMS. This initial major upgrade could also prepare the machine for further technical improvements that could allow it to reach a higher energy.”

Within the FP7 HiLumi LHC programme, the Japanese Laboratory KEK and the LARP network of US laboratories are partners in the design study alongside 14 European institutions. “We have set up a collaboration in which all partners are involved at the same level,” says Rossi. “While we were building the LHC, LARP and KEK were developing new technologies for the next generation magnets. Their research and development activities will be key to the success of HL-LHC.”

The 1 m long quadrupole developed by the US-LARP collaboration. During recent tests, the quadrupole successfully reached 13 T of magnetic field.

HL-LHC will rely on a number of key innovative technologies (see box), which represent exceptional challenges. They include: cutting-edge 13 tesla superconducting magnets, very compact and ultra-precise superconducting cavities for beam rotation, and 300-metre-long high-power superconducting links with nearly zero energy dissipation. “All these new technologies require further study but the project’s partners have the necessary know-how to successfully develop them,” explains Rossi. “At the kick-off meeting we will synchronize our work to increase synergies among the various laboratories involved in the project. We will touch base on what has been done so far, identify the state of the art in the different fields, and define future milestones.”

The HiLumi LHC project received a perfect score of 15/15 from the European Commission and was granted the whole amount of the requested funding. “The involvement of the non-European LARP and KEK laboratories will facilitate the implementation of the construction phase as a global project,” concludes Rossi. “The proposed governance model has been tailored accordingly and will pave the way for the organisation of other global research infrastructures.”

The new technologies involved in the HL-LHC

HL-LHC focuses on the following elements: new quadrupole magnets for the inner triplets (the magnets that are installed just before the collision points), new “crab” cavities (two per beam) to be installed on either side of CMS and ATLAS (point 5 and point 1 of the accelerator ring) to increase luminosity, an improved collimation system, and a cold powering system.

The LHC superconducting magnets that are currently in operation can produce a magnetic field of 8 tesla. The HL-LHC magnets will reach 13 tesla. The HiLumi LHC programme will review and assess the properties of two superconductors: Nb3Sn (niobium-tin) and Nb-Ti (niobium-titanium). The first offers better performance (higher critical temperature and field) but is more expensive and presents greater technical challenges.

The power converters are particularly delicate items of equipment that need to be protected from the radiation damage caused by the intense beams of HL-LHC. For this reason, the HL-LHC project includes moving them to the surface and installing 300-metre-long superconducting cables that will bring the power from the surface to the underground installations. The HiLumi LHC programme includes the study of the thermal and electrical performances of a long electrical transfer line cooled by supercritical helium. Different types of advanced conductors - MgB2, BSCCO 2223 and YBCO - are being analysed, as well as different cooling temperatures ranging from 10 K to 50 K.

In order to fully exploit the inner triplet upgrade, crab cavities are needed. These are the instruments of choice for optimum integrated luminosity and are probably the best means of levelling luminosity (to avoid extreme pile-ups that degrade data quality in the experiment). At present, there are a number of proposals for possible designs of Compact Crab Cavities – their detailed study will be part of HiLumi LHC work package number 4.


Public Session of the HL-LHC Project:

On Friday 18th November, a HiLumi LHC Public Session will take place in the main auditorium of CERN, please come along.


by CERN Bulletin