Engineering Science students invited to design for CERN’s Large Hadron Collider

In April, eleven Engineering Science students in their third year were invited to the CERN laboratory in Geneva to present their ideas for new vacuum chamber designs for the experiments of the Large Hadron Collider (LHC). Their design objectives were to propose alternatives to beryllium – the material used for some of the existing experimental vacuum chambers. Beryllium (chemical element with the symbol Be and atomic number 4) is toxic, expensive, difficult to machine and join, and can have associated health problems if personnel were exposed to the element in a particle form caused by damage to a chamber.

CERN Group 2012
Left photo: 3rd year students pictured here with their supervisors Professor Paul Buckley and Dr. John Huber. Right photo: The group with Ray Veness, Mark Gallilee, and Paul Cruikshank of the Vacuum Group at CERN.

The hadron beam at CERN's Large Hadron Collider is held in vacuum, and a structural vacuum chamber is needed around the entire 27 kilometre ring. It is paramount that, at the beam collision points, the chambers to be designed are transparent to particles created during a collision, so that the products can be detected, unimpeded, by the LHC experiments. Eleven Oxford students have worked in three teams and designed alternative systems to using beryllium. By exploiting advanced carbon composites they have developed alternatives with similar transparency but using safer materials. They also presented solutions for quick changeover of components, which could help minimise exposure of technicians to hazardous environments.

Ferrari F430 Challenge Brake
Example of carbon-carbon: the brake disc of this Ferrari race car’s braking system is made from carbon-carbon. (Image credit: The359, Wikipedia)
All three teams of students developed theoretical designs from intensive research based on their special knowledge acquired on their course coupled with other resources. Their research resulted in learning about carbon fibre-reinforced carbon (aka carbon–carbon), which has been used for the leading edges of the (now retired) Space Shuttle orbiter, and more recently in the braking systems of Formula One racing cars. It is a composite material consisting of carbon fibre reinforcement in a matrix of graphite.

Constance Mantle (Exeter College) said: "My team recommended carbon-carbon because it has comparable transparency to beryllium with an atomic number of 4, is able to maintain the ultra-high vacuum and has good thermal properties. Furthermore, it is safer and should be significantly cheaper to manufacture".

Constance added: "We have all found it exciting to do a live research project – many 3rd Year students don’t have an opportunity to visit a prominent research facility like CERN".

Antonella Gorenflos (Exeter College) said: "My team’s main considerations were to design a structure that would overcome the conflicting requirement for a material to be highly leak tight to air and transparent to scattered particles from within the chamber. The unprecedented nature of CERN’s task gave us ample opportunity to brainstorm for unconventional solutions, which can’t be sourced in papers or on the internet -the obstacles were unforeseeable! Our final design is a sandwich structure. The outer Carbon-Carbon layers provide stiffness whilst the aluminium foam in the middle improves the radiation length to a quality similar to that of beryllium. In order to calculate the optimum thickness of each layer and aluminium foam density we considered additional failure mechanisms of buckling and wrinkling in between layers".

Alexandra Roy (Oriel College) said: "My task within my team was to design the end seals that link the vacuum chambers.  These seals are located near the detectors (where particle collisions happen), and must be undone and resealed in the minimum of time, to limit technicians’ exposure to radiation. We recommended carbon-carbon as an alternative material to beryllium with a copper gasket and quick-release clamp design for the end seal".

CERN StudentsDr John Huber, who has been teaching this 3rd Year group, accompanied the students to CERN. He said: "This visit gave the students a rare opportunity to present their design ideas to the world’s experts. Students toured the vacuum laboratories, learnt how vacuum chambers were made and gained an insight into novel concepts being explored for future vacuum chambers".

Dr Huber added: "Students discovered that although CERN is outsourcing work with carbon-carbon composites, the capability to make a full vacuum chamber in-house in carbon-carbon would be a new direction.  Students provided the CERN team with food for thought e.g. to have an in-house furnace chamber (approx. 7 metres long) to make carbon-carbon".

Mark Gallilee (CERN Vacuum Group) said: "The CERN Vacuum Group is extremely happy to have continued our close collaboration with Oxford University Engineering Science department on this latest project. The students generated some interesting and novel ideas. These ideas will now be investigated, in line with our long-term goal to develop new technologies for the experimental vacuum chambers. This collaboration has been of great benefit to both the students and CERN".

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