LHC Photo: CERN / press materials.
The Large Hadron Collider is the most complex machine constructed by man. How does it work? What happens in the tunnels CERN?
This type of microscope that allows explore the world of the very small scales. This leads him to crash two moving in opposite directions beams of particles – protons or lead nuclei.
gram of hydrogen starczyłby million years
To the LHC work, you need a whole accelerator complex, gradually rozpędzających nuclear particles to larger energy. Everything starts from hydrogen, whose atoms are composed of one proton and one electron.
These atoms every few hours are taken from a small bottle and ionized, or “stripped” of electrons. The thus obtained protons are directed to a linear accelerator, where it accelerates until about 30% the speed of light. Then they go to the PS Booster accelerator and here their kinetic energy increases almost 30-fold. With Booster protons are transferred to the Proton Synchrotron PS, and then to the Super Proton Synchrotron SPS at every stage of higher energy approx. 20 times. Then, finally they get into the tunnel Large Hadron Collider.
Every day, the LHC accelerates just a few nanograms (10-9 g) of hydrogen. This means that this element would suffice play roughly a million years of operation of the accelerator.
electromagnets powerful as lightning
In the LHC, the particles are formed in two counter-rotating beams . They run in two parallel pipe several centimeters in diameter. Pipes were laid approx. 100 meters underground in a circular tunnel with a circumference of 27 km. To particles do not distract too fast for the gases inside the tubes (the entire length of the tunnel) ultrahigh vacuum prevails.
Ultimately protons in the LHC will be dispersed to the speed of approx. 0.999999991 speed of light, and every second lap tunnel over eleven thousand times. To force the particles with such large energies to the movement in the circular tunnel, you have to bend their paths through the magnetic field produced by more than 1,200 powerful electromagnets. The current flowing through the windings of the magnets has an intensity of several thousand amperes – like a small lightning surge.
The magnets in the LHC tunnel built of superconductors, or materials that at very low temperatures do not place electrical resistance. All superconductors are cooled to a temperature of just 1.9 degrees above absolute zero (this means that inside the LHC is colder than in open space). In addition to the dipole magnets, lead particles along the vacuum tube, the LHC is equipped with teams focusing and correcting magnets that prevent rozbieganiu footprints and focusing them at the collision point inside the detectors.
CERN – the master control of energy
The protons inside the accelerator circulate in packs of approx. 100 billion. The energy of all the packages circulating in the accelerator may correspond to energy explosion even 80 kg of TNT. The accelerator tunnel, in siedmiometrowych intervals, at the same time can circulate more than 5,600 such parcels. In the final configuration, both the proton accelerator beam power train will have a weight of 800 t, speeding the speed of 150 km / h. Controlling such a large energy for so complex a device is unique in the world of scientific and technical challenge.
When accelerating beams to the proper energy, the particles can circulate in the tunnel for many hours. The intensity of the beams gradually decreases due to the controlled collisions of beams in the detectors, and by the scattering of particles on the remains of the gas into the vacuum tubes.
After a few hours beams are emitted from the tunnel and directed to the graphite blocks, which precipitated his energy. During the collision the kinetic energy of the primary beam of particles (protons or lead nuclei) into the new, most unstable particles. The task is to identify the detector resulting in collisions of particles, measure their position in space, the electric charge, velocity, mass and energy. Really hard particles have lifetimes shorter than a picosecond and can not be observed in any of the detection system. Their study is possible only by analyzing the energy and shoots registered their degradation products.
Strictly controlled collision
The particles of the two counter-rotating beams collide with each other only in selected locations. The points of intersection of the beams detectors built four major experiments, ATLAS, CMS, ALICE and LHCb. ATLAS is the largest detector of the LHC. It contains eight superconducting magnet coils each 25 meters long, arranged in the shape of a cylinder around the tube bundle arranged in the middle of the detector. The entire ATLAS is 46 meters long, 25 meters high and 25 meters wide, weighs 7,000 tonnes. A little smaller CMS is nearly twice heavier. The maximum number of proton-proton collisions at the LHC can reach billions per second – a million times more cases than the man knows how to save. Therefore, special electronics make-to-date selection, separating collision interesting (to save) from dull.
(ew / NCBJ)
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