Exel Composites carbon fibre profiles deliver precision, performance and longevity at CERN


Carbon fibre components designed and manufactured by Exel Composites have successfully completed 9 years of service in a high precision application at CERN’s Large Hadron Collider (LHC) particle accelerator in Geneva. As a key part of the particle tracker support structures for the LHC’s Compact Muon Solenoid (CMS) detector, Exel’s pultruded profiles had to satisfy strict dimensional tolerances and sustain the highest level of performance in this extremely challenging environment, where any downtime or failure would impact major scientific experiments.

The LHC is the world’s largest and most powerful particle accelerator. It consists of a 27 km ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way. Inside the accelerator, two high-energy proton beams travel at close to the speed of light, in opposite directions, before they are made to collide at four locations around its ring. The CMS detector sits at one of the four collision points and records the paths taken by particles using a silicon tracker consisting of around 75 million individual electronic sensor channels arranged in 12 concentric layers. The tracker needs to record particle paths with very high precision yet be lightweight so as to disturb the particles as little as possible.

The Exel Composites components are part of the 688 high-precision structures supporting the silicon tracker modules. These are made up of two 1,2 m long Exel carbon fibre epoxy composite U-profiles of 0.7 mm wall thickness and L-shaped cross-bars to form a frame structure on which the particle detecting modules sit. In addition to delivering the lightweight and radiation transparency required for this application, it was critical that the Exel profiles met extremely tight tolerances in terms of dimensions and straightness and maintained all mechanical properties at the low temperatures encountered in the CMS. In order to provide the high levels of stiffness and thermal stability required Exel designed the profiles using high modulus unidirectional (UD) carbon fibre. A thin glass fibre surface tissue was also employed to facilitate processing. All of the components and fixtures were then assembled and bonded on jigs at the Helsinki Institute of Physics to create structures with a dimensional tolerance of ± 0.05 mm.

Exel’s proven capabilities in the production of high performance thin-walled pultruded profiles and the company’s extensive experience in designing with high modulus carbon fibres were key success factors in this project. Exel had also collaborated successfully with CERN before, supplying around 200 km of electrically insulating glass fibre profiles to frame the superconductive busbars of the LHC.

Exel delivered the tracker support profiles to CERN from 2001 to 2005, with the final operational use starting in 2008. The CMS detector has been performing excellently, culminating in 2012 at the discovery of a new elementary particle, the Higgs boson.

“We are very satisfied with the high level of technology and development support offered by Exel Composites,” comments Antti Onnela, CMS Tracker Project Engineer at CERN. “We had quite challenging requirements for these composite structures and earlier laminated versions did not meet them. Exel developed the needed thin-walled U-profiles that turned out to be technically superior, but also more economical thanks to the production process that minimised the wastage of expensive carbon-fibres. After 9 years in service in CMS the Exel parts continue performing as flawlessly as in the beginning.”

“We are very proud that Exel profiles have delivered the precision and performance essential for the operation of this extremely complex instrument,” says Kari Loukola, Senior Vice President, Sales & Marketing, Exel Composites. “This project is a further example of how our pultrusion technology enables the production of profiles of superior quality which will provide customers with reliable performance in the most demanding of environments for many years to come.”

Exel Composites

Exel Composites (www.exelcomposites.com) is a leading composites technology company that designs, manufactures and markets composite products and solutions for demanding applications. Exel Composites provides superior customer experience through continuous innovation, world-class operations and long-term partnerships.

The core of Exel’s operations is the company’s proprietary composite technology, product range and strong market position in selected segments with a strong quality and brand image. Profitable growth is pursued by a relentless search for new applications and development in co-operation with customers. The personnel’s expertise and high level of technology play a major role in Exel Composites’ operations. Exel Composites Plc shares are listed on Nasdaq Helsinki Ltd.


CERN (http://home.cern), the European Organization for Nuclear Research, is one of the world’s leading laboratories for particle physics. The Organization is located on the French-Swiss border, with its headquarters in Geneva. At CERN, physicists and engineers are probing the fundamental structure of the universe. They use the world’s largest and most complex scientific instruments to study the basic constituents of matter – the fundamental particles.