Electromagnetic Cascades At the energies involved in the process that take place in the upper atmosphere when a -ray plunges into the atmosphere the pair production is the dominant effect. This is the situation in EAS. The process of pair production takes place in the field of an atmospheric nuclei or electron in order to conserve momentum. A high energy photon, of at least an energy of 1.022 MeV, in matter converts into an electron and positron pair. If the energy is sufficient, the resulting electron pair does not quickly lose its energy by ionizating interactions. Instead, an electron in the field of a nucleus can produce a secondary gamma ray. This process is called bremsstrahlung. This gamma ray, if its energy is still higher than 1.022 MeV, can then produce another electron pair that can undergo further bremsstrahlung interactions. The result is a cascade of photons, electrons and positrons, which continues traveling in the original direction of the primary gamma ray and sharing its total energy.
Posted on: Mon, 08 Sep 2014 22:42:16 +0000
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