Ten amazing facts about the LHC

The LHC (large hadron collider) is the biggest machine ever built by humans. Check below these 10 amazing facts about the LHC that will blow your mind.



Fact 1 - When the 27-km long circular tunnel was excavated, between Lake Geneva and the Jura mountain range, the two ends met up to within 1 cm. The LHC re-uses the 27-km circumference tunnel that was built for the previous big accelerator, LEP. The tunnel was built at a mean depth of 100 m, due to geological considerations (translating into cost) and at a slight gradient of 1.4%. Its depth varies between 175 m (under the Jura) and 50 m (towards Lake Geneva).

Fact 2 - Each of the 6000-9000 superconducting filaments of niobium-titanium in the cable produced for the LHC is about 0.007 mm thick, about 10 times thinner than a normal human hair. If you added all the filaments together they would stretch to the Sun and back six times with enough left over for about 150 trips to the Moon. Superconductors are key for the construction of the 9600 magnets. Each type of magnet contributes to optimizing a particle’s trajectory, and offset the effect of the tides. Not everybody knows that the Earth’s crust rises by some 25 cm in the Geneva area under the effect of these ‘ground tides’. This movement causes a variation of 1 mm in the circumference of the LHC (for a total circumference of 27 km) and this produces changes in beam energy and trajectory.

Fact 3 - All protons accelerated at CERN are obtained from standard hydrogen. Although proton beams at the LHC are very intense, only 2 nanograms of hydrogen*) are accelerated each day. Therefore, it would take the LHC about 1 million years to accelerate 1 gram of hydrogen.

Fact 4 - The central part of the LHC is the world’s largest fridge. At a temperature colder than deep outer space, it contains iron, steel and the all important superconducting coils. 120 t of helium are required by the LHC machine to keep the magnets at their operating temperature of 1.9 K.

Fact 5 - At the same time, LHC can reach unbelievable hot temperatures, more than 100.000-times the temperature at the center of the Sun. This is achieved by accelerating and colliding together two beams of heavy ions, an epic scientific event that takes place every day, 40 million times per second.

Fact 6 - The pressure in the beam pipes of the LHC is about the atmosphere of the Moon. This is an ultrahigh vacuum. The beam vacuum pressure is 10–13 atm because we want to avoid collisions with gas molecules. The largest volume to be pumped in the LHC is the insulation vacuum for the cryomagnets (~ 9000 m3, like pumping down the central nave of a cathedral!)

Fact 7 - Protons at the design energy in the LHC travel at 0.999999991 times the speed of light. Each proton goes around the 27 km ring more than 11 000 times a second. A beam might circulate for more than 10 hours, traveling more than 10 billion kilometers, enough to get to the planet Neptune and back again. The particles are so tiny that the task of making them collide is like firing two needles 10 kilometers apart with such precision that they meet halfway.

Fact 8 - At full energy, each of the two proton beams in the LHC has a total energy equivalent to a 400 t train (like the French TGV) traveling at 150 km/h. This is enough energy to melt 500 kg of copper. In absolute terms, these energies, if compared to the energies we deal with every day, are not impressive. 1 TeV is about the energy of motion of a flying mosquito. What makes the LHC so extraordinary is that it squeezes energy into space about a million million times smaller than a mosquito.

Fact 9 - The CMS magnet system contains about 10000 t of iron, which is more iron than in the Eiffel Tower.

Fact 10 - The data recorded by the big experiments at the LHC are enough to fill around 50000 1 TB hard disks every year or corresponding to a stack of about 10 million standard DVDs, about 12 km tall each year.


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