I mean, why IS, instead of was. Can't edit!

It was built in the tunnel originally dug for an earlier Collider, which saved the cost of a new tunnel. It is the latest in a series of particle research tools built at Cern. Cern was set up on the French/Swiss border as a good place for a pan-European co-operative venture: it is paid for by a large number of countries, most of them in Europe.

The greater the radius, the easier it is to keep the beam curvature without losses (synchrotron radiation losses). "In the circular accelerator, particles move in a circle until they reach sufficient energy. The particle track is typically bent into a circle using electromagnets. The advantage of circular accelerators over linear accelerators (linacs) is that the ring topology allows continuous acceleration, as the particle can transit indefinitely. Another advantage is that a circular accelerator is relatively smaller than a linear accelerator of comparable power (i.e. a linac would have to be extremely long to have the equivalent power of a circular accelerator)." "At present the highest energy accelerators are all circular colliders, but it is likely that limits have been reached in respect of compensating for synchrotron radiation losses for electron accelerators, and the next generation will probably be linear accelerators 10 times the current length. An example of such a next generation electron accelerator is the 40 km long International Linear Collider, due to be constructed between 2015-2020." Source and further information: http://en.wikipedia.org/wiki/Particle_accelerator Further information: http://en.wikipedia.org/wiki/Large_Hadron_Collider