CERN Accelerating science

From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules

The first concepts of the HL-LHC crab cavities started more than 10 years ago. They were the fruit of the discussions of a young physicist at BNL and a beam dynamics expert at CERN. The concept was not new but using it for the LHC implied a long journey of technological challenges.

The distance between the LHC beams required a new RF concept for particle deflection with a novel shapes and significantly smaller in size than conventional RF cavities. The challenge was taken with enthusiasm by the RF community resulting no less than 10 concurrent designs from RF experts across three continents. In 2013, three designs were considered to be the most adapted to the LHC and became ready for the development of a proof of principle. While this may sounds like a moment of fierce competition, in reality it showed the spirit of cooperation towards a common goal among the members of our community. The results of the RF tests of the Double Quarter Wave (DQW), the RF Dipole (RFD), and the four Rod (4R) were highly promising and analysed by an international panel in 2014 that recommended to focus the efforts on the first two designs to make a full validation of the cryomodule in the CERN’s SPS.

One of the crab cavities that will be used in the HL-LHC (Image Credit: CERN)

The entire community concentrated on the two designs and on the development of the concept of all the other required components of the cryomodule that should host the cavities. The effort that had already started in 2013 by CERN required the knowledge, experience and imagination of the collaboration.

In fact, 2015 became a decisive year that started with a collaborative design thinking of the most innovative components. Among them we can highlight the frequency tuning system, the helium tank and the RF lines, all of which required inspiration beyond the conventional wisdom to adhere to the strict needs of HL-LHC. There is a global consensus on the fond memories of the design phase in 2015, wild enthusiasm and collaboration. Effectively, during this extremely critical period every team contributed to the design before concentrating on the detail development of the different components. The result was as harmonic as the sound of a good symphonic orchestra. A robust design that was flexible to be used for the test of the cryomodule at the SPS, easily adaptable for the LHC and that could be transferred to the industry for the series production.

Today the first cryomodule is finished and under cold test without any delay on the manufacturing plan that was prepared more than two years ago. A plan that at that moment was considered almost impossible. Today, the infrastructure in the SPS is ready and just waiting for the cryomodule installation. The hard work of these last 5 years of engineers and physicists from US, UK and CERN will reap the benefits of their hard efforts.

In the meantime, the team is thinking about the future. In December the industrial contract for the series production of the cavities under CERN’s responsibility will be adjudicated. The global collaboration will be further enlarged with discussions with laboratories in Canada and in Japan willing to contribute to the construction of the cryomodule.

A global effort and we hope a global success!

Luis Antonio González (CERN)
A novel beam screen technology for FCC-hh
31 Mar 2020

A novel beam screen technology for FCC-hh

EuroCirCol project delivers an overall integrated design for the cryogenic beam vacuum system for the challenging environment of a future 100 TeV circular proton collider.

Stéphanie Vandergooten
Apply now to the Joint Universities Accelerator School
23 Sep 2019

Apply now to the Joint Universities Accelerator School

Interested to learn more about Particle Accelerators? Apply now to the 2020 JUAS School in Archamps to follow 5-week courses on particle accelerators.

Anaïs Schaeffer
Aligning the HL-LHC magnets with interferometry
4 Dec 2019

Aligning the HL-LHC magnets with interferometry

CERN surveyors have developed a procedure based on interferometry to determine the position of cold masses inside the cryostats of the future HL-LHC.

A bright future for HL-LHC

The 7th HL-LHC Annual meeting in Madrid took place in November. An intensive week to review the progress done during 2017 and the objectives for 2018. The HL-LHC project is moving to construction phase. The hardware models as well as the prototypes of the equipment in their final configuration are under construction or currently tested. 

In 2017, the HL-LHC project achieved a number of key milestones. The first crab cavity prototypes built in the US were successfully tested by LARP collaboration that is transforming into US-HL-LHC AUP (Accelerator Upgrade Programme) and the full cryomodule containing the crab cavities built at CERN was successfully tested at 2K; just in time to be integrated in the SPS during the winter where their performance will be studied next year by using a beam from the SPS.

The first low impedance collimators were tested and characterized in the LHC machine together with the crystal collimation concept (not in HL-LHC baseline). The test of the first long prototype of the MQXF quadrupole, manufactured by US-LARP-AUP for the new low-b HL-LHC insertions has just started in BNL. The first results are expected in February. Moreover, the construction of the first 11 T magnet and DS collimator and the test of the first long SC link, all manufactured at CERN, were among the highlights of the HL-LHC week.

In addition, the successful implementation of the ATS optics (devised for the LHC upgrade) and the tests of the full detuning operation mode of the LHC RF system during the LHC operations: are two key ingredients that increased the performance of the LHC in 2017 and pave the way for its high-luminosity upgrade.

This year we had an international review that validated technically the e-lenses and equipment that could be part of the HL-LHC baseline. Finally, we have concluded on the interface between the machine and the experiments. These above developments in all these different fields show how the HL-LHC project is making progress towards final implementation.

There are several other relevant milestones achieved by the HL-LHC collaborations. The short model of the D1 reached ultimate current in KEK. The first octupole and decapole prototypes also went beyond the ultimate current in INFN LASA. The D2 model construction in the industry is well advance, a collaboration led by INFN. Finally the short mechanical model of the nested orbit corrector and the first coil were also accomplished this year in CIEMAT

Procurement for HL-LHC

2017 was also the year for the preparation and adjudication of some of the bigger contracts of HL-LHC. The tender for civil engineering works for Point 1 and Point 5 (including large excavation and construction work) was announced in July and is presently under final evaluation. The contract adjudication will be done in March and the first civil works for HL-LHC are expected to start in summer 2018.

This year has also seen the first tender for the collimators that will be installed during the next Long shutdown 2 (LS2). The adjudication in December will ensure their delivery on time for their installation before mid-2020. In parallel to the construction of the crab cavities cryomodule to be tested in the SPS in 2019, the tendering of the Jacketed Crab Cavities DQW type has been placed. The contract will be adjudicated this December and will be complemented by the work done by AUP on the RFD type crab cavities. Also in the field of the 11T magnets, HL-LHC adjudicated the tender for the construction on CERN site of the coils for the 11T dipole. An industrial service contract where skilled employees will use the facilities built at CERN and that were used to build the first models and prototypes of the 11T dipole.

The next challenge for HL-LHC is to ensure a coherent integration lay-out that will meet the constraints imposed by the lay-out of the civil engineering and the preparation of a first version of the installation plan. Meanwhile, the optimization of the design and construction of the components is in progress. “As the window to keep various options in the planning narrows we need to work hard to make final choices for the implementation of an industrial construction roadmap” says Lucio Rossi HL-LHC Project Leader.  

The second HL-LHC Collaboration Board also took place during the HL-LHC week. HL-LHC steadily becomes a global project. 18 HL-LHC Collaboration Board members and 11 collaboration partners with R&D contributions work together with CERN to make possible HL-LHC. The gathering in Madrid showed the interest of the community on the development of the HL-LHC technologies with multiple proposals for in-kind contributions.

To learn more about the HL-LHC Project read the Technical Design Report (TDR) and or brand new website .


*AUP HL-LHC Accelerator Upgrade Project (BNL, FNAL, LBNL and SLAC)

A. Latina, G. D’Auria and R. Rochow (CERN)
Improving access to FEL facilities through the CompactLight project
12 Jul 2019

Improving access to FEL facilities through the CompactLight project

One of technologies used by CompactLight is the high-gradient normal conductive RF acceleration in the X-band, developed at CERN within the context of the CLIC study.

Marco Zanetti (INFN & Univ. Padua), Frank Zimmermann (CERN)
Workshop shines Light on Photon-Beam Interactions
7 Dec 2017

Workshop shines Light on Photon-Beam Interactions

The ARIES Photon Beams 2017 Workshop was held in Padua, Italy in late November 2017.

Panos Charitos, Frank Zimmermann
Unfolding the full potential of a future circular lepton collider
9 Dec 2019

Unfolding the full potential of a future circular lepton collider

A recently proposed acceleration scheme could further increase the performance of a technology-ready circular lepton collider and boost the exploratory potential of the FCC integrated programme.