Real Physics: The Large Hadron Collider
Real physics: the LHC:
BBC NEWS | Science/Nature | Energising the quest for 'big theory' : "We are at a point where experiments must guide us, we cannot make progress without them," explains Jim Virdee, a particle physicist at Imperial College London. "We must wait for the data to speak." Over a coffee in the lobby of building 40 at Cern, the sprawling experimental facility situated on the Swiss-French border, Professor Virdee says physics has reached a critical juncture. In the 1970s, the theory known as the Standard Model was considered a triumph of theoretical physics, incorporating all that was then known about the interactions of sub-atomic particles. Today it is regarded as incomplete, a mere stepping stone to something else.
The Standard Model cannot explain the best known of the so-called four fundamental forces: gravity; and it describes only ordinary matter, which makes up but a small part of the total Universe. The $2.3bn Large Hadron Collider (LHC) at Cern (The European Centre for Nuclear Research), which is paid for by contributions from Cern's European member countries (including the UK), should reinvigorate physics' biggest endeavour: a grand theory to describe all physical phenomena in nature. About 100m below us, in a tunnel that runs in a ring for 27km (17 miles), the LHC is being assembled from its constituent parts like a vast, impossibly complex Meccano set. When it is switched on for a pilot run in summer 2007, this vast physics experiment will collide two beams of particles head-on at super-fast speeds, recreating the conditions in the Universe moments after the Big Bang. The beam collisions should create showers of new particles, revealing new physics beyond the Standard Model. In order for that to happen, the LHC needs to reach much higher energies than previous colliders.
The particle beams, composed of either protons or lead ions, will be created in Cern's existing chain of particle accelerators and then injected into the LHC. Here they will receive an additional electrical impulse to boost them up to their final energy of seven trillion volts. Some 1,232 "dipole magnets" will carry these high energy beams through their interior and bend it around the LHC. Each one undergoes a rigorous quality test before it can be lowered into the tunnel. At the Cern site known as Point 18, Dr Mike Lamont, from Cern's beam operations group, shows us round the hangar-like facility where the magnets are put through their paces, 12 at a time. The tests are run at 1.9 Kelvin (-271C), the eventual operating temperature of the LHC.... The magnets are cooled to this ultra-low temperature by bathing them in liquid helium.