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Tuesday, 10 August 2010



The history of antimatter begins with a young physicist named Paul A.M.Dirac (1902-1984) and the strange implications of a mathematical equation. This British physicist formulated a theory for the motion of the electrons in electric and magnetic fields. Such theories had been formulated before, but what was unique about Dirac’s was that his included the effects of Einstein’s Special Theory of Relativity. This theory was formulated by him in 1928.Mean while he wrote down an equation, which combined quantum theory and special relativity, to describe the behavior of the electron. Dirac’s equation won him a Nobel prize in I 933,but also posed another problem; just at the equation x2 = 4 can have two solutions (x 2, x = -2). So Dirac’s equation would have two solutions, one for an electron with positive energy, and one for an electron with negative energy. This led theory led to a surprising prediction that the electron must have an “antiparticle” having the same mass but a positive electric charge.

1n 1932, Carl Anderson observed this new particle experimentally and it was named “positron”. This was the first known example of antimatter. In 1955, the anti proton was produced at the Berkeley Bevatron, and in 1995, scientists created the first anti hydrogen atom at the CERN research facility in Europe by combining the anti proton with a positron Dirac’s equation predicted that all of the fundamental particles in nature must have a corresponding “Antiparticle”. In each case, the masses of the particle and anti particle are identical and other properties are nearly identical. But in all cases, the mathematical signs of some property are reversed. Anti protons, for example have the same mass as a proton, but the opposite electric charge. Since Dirac’s time, scores of these particle-antiparticle pairings have been observed. Even particles that have no electrical charge such as the neutron have anti particle.


Anti protons do not exist in nature and currently are produced only by energetic particle collision conducted at large accelerator facilities (e.g. Fermi National Accelerator Laboratory, Fermi Lab, in US or CERN in Geneva, Switzerland). This process typically involves accelerating protons to relativistic velocities (very near to speed of light) and slamming them into a metal (e.g. Tungsten) target. The high-energy protons are slowed or stopped by collisions with nuclei of the target; the kinetic energy of the rapidly moving protons is converted into matter in the form of various subatomic particles, some of which are anti protons. Finally, the anti protons are electro magnetically separated from the other particles, then they are captured and cooled (slowed) by a Radio-Frequency Quadrapole (RFQ) linear accelerator (operated as a decelerator) and then stored in a storage cell called as a Penning Trap.

Note that anti protons annihilate spontaneously when brought into contact with normal matter, thus they must be stored and handled carefully. Currently the highest anti proton production level is in the order of nano-grams per year.


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