Why build the Large Hadron Collider? - page 2
Keywords: Physics Report Large Hadron Collider Basic Introduction Grand Unified Theory Cosmic Rays Anti Matter Extra Dimensions String Theory Dark Matter Higgs Boson
By Jenny on 02/07/2009
Level: A Level (Year 13)
Page Number: 2 of 16 pages: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
as a result of these collisions. He used a lead Collimeter to fire a fine stream of alpha particles at what were then high energies (a few MeV, produced in the radioactive decays of heavy elements) at atoms (an extremely thin gold foil) and then used a sheet of ZnSe to detect them (ZnSe fluoresces on contact with alpha particles). He found that the overwhelming no. of alpha particles went straight through the foil with no deviation at all, a very small no. were deflected through small angles and even fewer were deflected through large angles. These observations lead him to formulate a new model of the atom (the nuclear model) with the overwhelming amount of the ‘volume’ of an atom being empty space and most of the mass concentrated in a tiny positively charged nucleus.[4]
Modern particle accelerators still use much the same principle just with higher energies (about 100,000 times more than that available in radioactive decays per beam particle) colliding particles together to see what will happen.
These higher energies are achieved by using electrical forces to accelerate the beam particles, so the beam particles must be charged. In practice this means using either electrons or protons, or their anti-particles, positrons or antiprotons.[1]
The LHC, which when completed will be the worlds most powerful particle accelerator, will use protons initially with experiments using heavy ions later, accelerating two beams in opposite directions to expected energies of 7 TeV per beam for proton-proton collisions (about a million times larger than the energies from radioactive decay).
When the beams cross the goal is to have protons from one beam collide with protons from the other (hence the name ‘Collider’) giving total collision energies of 14 TeV.[1]
For most of the ring the beams will travel in two separate vacuum pipes, but at four points they will collide, deep inside the four main LHC experiments (ATLAS, CMS, ALICE and LHCb), which will carefully monitor the collisions and their products searching for signs of among other things, supersymmetry, dark matter and the origins of mass. [1][6]
The detectors could see up to 600 million collision events per second, as the beams are made up of bunches containing billions of protons and travel at just below the speed of light. The beams will be injected, accelerated, and kept circulating for hours inside a continuous vacuum, guided by thousands of powerful superconducting magnets, which will be cooled
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