Proton radiation

Proton radiation - radiation, consisting of a stream of protons (see Atom). Proton radiation is the main part of cosmic rays (see). In terrestrial conditions in charged particle accelerators (see) receive protons different energies. Being positively charged particles, protons when passing through matter interact with negatively charged electrons of atoms and pull them up with electron shells. This causes ionization (see ionizing Radiation) atoms of substance. The density of ionization protons increases dramatically at the end of the run particles. Thanks to this property the protons is convenient to use in radiation therapy (see Proton therapy) for selective irradiation of deep-seated tumours (for example, the pituitary). The high-energy protons have a small angle scattering, which also contributes to the localization of the dose in a single place. The high-energy protons to overcome the Coulomb repulsion, get to the core and cause various nuclear reactions, which are formed of secondary radiation - neutron, gamma rays , and others In this regard when irradiated substances protons to high energies, the ionization of the environment is not only due to primary protons; but at the expense of the secondary radiation. This fact should be taken into account when calculating doses created proton radiation.

Proton radiation - flux of positively charged atomic particles - protons. First proton radiation discovered in 1886 in the form of so-called Kamalovich beams in vacuum tubes.
Sources of intense proton radiation are charged particle accelerators (see). Using accelerators obtained beams P. I. with energies in the tens of billions of electron volts. Even greater energy P. I. meet in space. P. I. is the main component of galactic and solar cosmic radiation. Intensive streams P. I. detected in the near-earth space, called the Earth radiation belts.
The ability P. I. to penetrate through the layers of matter depends on the energy of the proton beam (see) and the properties of substances. P. I. with energy 10 MeV able to pass a layer of air (at normal temperature and pressure) of about 1 m With increasing energy P. I. up to 1000 MeV layer thickness reaches almost 3 km
In heavy substances PP delayed more thin layers. So, in the lead P. I. with energy 10 MeV is about 1/3 mm and 1000 MeV - somewhat less than 60 see Proton radiation with energies above 100 MeV can penetrate the body to a depth of 10 cm and more. The biological effect of proton radiation with an energy of hundreds of million electron volts in acute irradiation in General similar to the action of x-ray and gamma-radiation.
However, the biological effect of protons of energies has some peculiarities in comparison with x-ray and gamma radiation (less distinct reaction from the blood-forming organs in the early stages, most severity of hemorrhagic syndrome and others). At relatively low energies biological effectiveness P. I. higher than that of x-ray and gamma-radiation. This is due to higher ionizing ability of such protons. Unlike x-and gamma-rays, protons, passing through biological tissue, is capable of producing nuclear reaction. As a result of nuclear reactions secondary particles are formed with high ionizing ability, which leads to the absorption in the small amount of tissue is relatively large amounts of energy and to the relevant local defeats tissue. This fact may be due to greater blastomogenic action P. I. compared with x-ray and gamma-radiation.
To protect against proton radiation is the use of substances, effectively inhibiting the protons to form relatively few of secondary particles in nuclear interactions (graphite, concrete, aluminum and others). Cm. Nuclear reactions.