The LHC is the next step in a voyage of discovery which began a century ago. Back then, scientists had just discovered all kinds of mysterious rays, X-rays, cathode rays, alpha and beta rays. Where did they come from? Were they all made of the same thing, and if so what?
These questions have now been answered, giving us a much greater understanding of the Universe. Along the way, the answers have changed our daily lives, giving us televisions, transistors, medical imaging devices and computers.
On the threshold of the 21st century, we face new questions which the LHC is designed to address. Who can tell what new developments the answers may bring?
Where is it?
The LHC is being installed in a tunnel 27 km in circumference, buried 50-175 m below ground. Located between the Jura mountain range in France and Lake Geneva in Switzerland, the tunnel was built in the 1980s for the previous big accelerator, the Large Electron Positron collider (LEP). The tunnel slopes at a gradient of 1.4% towards Lake Geneva.
What will it do?
The LHC will produce head-on collisions between two beams of particles, either protons or lead ions. The beams will be created in CERN's existing chain of accelerators and then injected into the LHC. These beams will travel through a vacuum comparable to outer space. Superconducting magnets operating at extremely low temperatures will guide them around the ring. Each beam will consist of nearly 3000 bunches of particles and each bunch will contain as many as 100 billion particles. The particles are so tiny that the chance of any two colliding is very small. When the particle beams cross, there will be only about 20 collisions among 200 billion particles. However, the particle beams will cross about 40 million times per second, so the LHC will generate about 800 million collisions per second.
How powerful?
The LHC is a machine for concentrating energy into a very small space. Particle energies in the LHC are measured in tera electronvolts (TeV). 1 TeV is roughly the energy of a flying mosquito, but a proton is about a trillion times smaller than a mosquito. Each proton flying round the LHC will have an energy of 7 TeV, so when two protons collide the collision energy will be 14 TeV. Lead ions have many protons, so they can be accelerated to even greater energy: the lead ion beams will have a collision energy of 1150 TeV. At full power, each beam will be about as energetic as a car travelling at 2100 kph. The energy stored in the magnetic fields will be even greater, equivalent to a car at 10 700 kph. At near light-speed, a proton in a beam will make 11 245 turns per second. A beam might circulate for 10 hours, travelling more than 10 billion kilometres � far enough to get to the planet Neptune and back again.
With a budget of 9 billion US dollars (approx. €7.5bn or £6.19bn as of Jun 2010), the LHC is one of the most expensive scientific instruments ever built.Data produced by LHC as well as LHC-related simulation will produce a total data output of 15 petabytes per year i.e 4 gigabyte per second.
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