Positron elementary particle with the mass of the electron, which has a charge of +1. Positron exist until then while not losing speed. At a speed close to zero, he unites with the nearest electron; this of the two particles are formed two ' -quanta with energy of 0.51 MeV, flying in opposite directions (the effect of annihilation). The positron is formed at interaction with matter ' -quanta with energy more than 1.02 MeV: in the field of the atomic nucleus such ' -quantum can form two particles - positron and an electron (this phenomenon is called the effect of education couples - see Gamma rays). When interacting 7-rays high-energy secondary space radiation with atoms of air formed avalanche ' -quanta and pairs of particles due to the sequential process of annihilation and education pairs (see Cosmic radiation). Positrons emitted when positron decay artificially radioactive isotopes with an excess of protons in the nucleus. One of protons kernel turns into a neutron, a positron, and a neutrino. Electron and positron emission together constitute beta radiation (see), and electronic and positronic decay - beta-decay. Positron interacts with matter as an electron that is another form along the path of movement of a large number of ion pairs, the density of ionization increases inversely proportional to the speed and reaches its maximum near the end of the run P. (see ionizing Radiation).