The invention that is shaping Linac4

Accelerator experts are no strangers to innovative optimizations of existing techniques and to the development of novel solutions. Sometimes, they even come up with ideas that have the potential to revolutionize the field. This is the case with the Tolerance Aligned Cantilever Mounting (TACM) system, a completely new way of supporting the drift tubes, one of the core elements of linear accelerators. The new, patent-pending technique will be implemented at Linac4.


Drift tubes in a prototype for Linac4, assembled using the new TACM technology.
“Assemble and adjust” – that was the technique used to build drift-tube linacs before the arrival of the TACM. Now, the inventors’ motto has become ‘adjust and assemble’. The inversion of these two words represents a real revolution for people working in the field. “The drift tubes are a critical element of Linac4 and they have to satisfy several requirements: they have to be mechanically stable and very reliable. And they must need very little maintenance over the years as they are at the beginning of the injection chain for the larger accelerators”, says Maurizio Vretenar, Linac4 project leader. “We started from two different design solutions but very quickly realized that, in order to meet the requirements, we needed something new”.

After several brainstorming meetings with the experts from the CERN Design Office, Pierre Bourquin and Yves Cuvet, and subsequent prototyping, the TACM came to life. “With this new technique, we make all the adjustments to the drift tubes’ positioning and alignment before installing them in the vacuum tank. In this way, we achieve a very high accuracy – better than one tenth of a millimetre – while ensuring leak-tightness and good electric contacts”, explains Suitbert Ramberger, project engineer for the Linac4 drift tube linac. The alignment of the drift tubes (see illustration) is an extremely critical parameter for a linear accelerator as any imperfection in the assembly and positioning process can potentially lead to beam losses.

Some acceleration facilities under construction around the world, such as the ESS test facility in Bilbao (Spain) and the large European Spallation Source (ESS) in Lund (Sweden), are potential users of the TACM technology of Linac4 developed at CERN. “At the beginning we presented our new ideas and methodologies at the various conferences but we soon realized that this technology could also be of interest to companies that build accelerators used in fields other than fundamental research”, says Maurizio Vretenar.

To protect the original ideas and also have some control over who uses them, CERN has filed a patent application for the new technology. “Our policy is to allow free access to CERN’s collaborating partners, but having a patent will increase the commercial potential of the technology and give us better control of the dissemination. Our aim is to make this technology available to others”, confirms Henning Huuse, Patent Portfolio Manager.

If you are at CERN and are in the process of inventing a new technology or have found an innovative solution to a process, read the next article and do not hesitate to contact the KTT group. It’s easy, straightforward and rewarding!

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Please follow the link for more technical information and the drawings of the TACM technology


by CERN Bulletin