TJ Exclusive – Up to nine TBMs for new Collider

Up to nine TBMs could be needed by 2016 to bore a 50km long, 5.6m i.d. hard rock tunnel for a new Linear Electron/Positron Collider currently being studied at Switzerland’s CERN complex, Tunnelling Journal can reveal.

Presently there are two options for the Linear Collider, but only one will be chosen to help further research into particle physics being undertaken at Switzerland’s world famous CERN Large Hadron Collider.

The two options, now at the feasibility stage, are CLIC, or the Compact Linear Collider, which has a typical tunnel i.d. of 5.6m for its 50km tunnel, and the ILC, the International Linear Collider that features a 31km long tunnel in a first phase, possibly extended by another 20kms later.

“The construction schedule depends on physics results from the CERN Large Hadron Collider. It will take at least 2 years for physicists to analyse the data, then the community will decide whether to build ILC or CLIC,” John Osborne, CERN Civil Engineering Project Manager, told Tunnelling Journal, “Probably the earliest the international tenders for construction could go out is around 2015. After that there’s an approximate 7 year construction schedule.”

At present, and vitally, there is no definite location for the Collider that’s chosen for construction.

“Both of these projects could be built anywhere in the world.

At the moment we’re doing feasibility studies and will come up with a standard cost for the ideal tunnel conditions, then the individual countries will tender (to host the facility) if they are interested.”

Currently several sites in Japan have shown interest, America has put forward the Fermilab facility area near Chicago, and Europe’s official sites are at CERN and in Russia. But more countries are expected to put themselves forward as potential hosts as the project gains momentum. Each will then bid to house the facility chosen, with the winning bidder funding the project’s cost of US$6.7bn estimated for the first phase of the ILC. The ‘which Collider and where’ question won’t dramatically affect the tunnel design though, as Osborne pointed out, “For us it doesn’t really make much difference, they are both single tunnel solutions through similar rock. More or less the same TBM numbers will be used erecting a pre-cast segmental lining, whichever the choice.”

The project is likely to be let using a FIDIC type contract set up, as was used on CERN’s LHC.

“I imagine it will be something similar, a re-measurement type contract. The problem is the physicists are always changing their minds, not intentionally, it’s just technology changes and they realize it wasn’t quite what they wanted, so a re-measurement contract is better than a turnkey, lump sum partnering set-up, for its flexibility,” said Osborne.

The question is, why do we need a completely new, straight tunnel, rather than the circular one used for the LHC?

“Because the next machine after the LHC will collide different kinds of particles – very light electrons and their antiparticles,” explained Osborne, “They require a completely different technology to be accelerated, and the most efficient way to do this is in a linear collider.”

The linear collider will complement the CERN LHC. Scientists expect many exciting discoveries to come out of the LHC, and a linear collider will be able to study the new particles and phenomena in much more detail. That’s also why they will have to wait for the first new results from the LHC before knowing which linear collider to build, and where to build it. Once it’s running, the science community will hope it will tell the world more about the complexities of things like dark matter, dark energy and even the illusive Higgs boson.

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