an area of applied physics that studies the physical values that characterize the effect of ionizing radiation on natural objects (animate and inanimate)—in particular, radiation doses—and the methods and instruments for measuring these amounts.

The development of dosimetry was spurred initially by the need to protect man against ionizing radiation; biological effects that appeared after the irradiation of man were noted soon after the discovery of X rays. The need arose for a quantitative evaluation of the degree of radiation danger. The basic quantitative criterion was taken to be the exposure dose, measured in roentgens and determinable in terms of the amount of atmospheric ionization. The work of Soviet scientists P. N. Lukirskii, V. M. Dukel’skii, D. N. Nasledov, K. K. Aglintsev, and I. V. Poroikov was important in the development of roentgenometry.

With the discovery of radium it was learned that the beta and gamma radiations of radioactive substances bring about biological effects similar to those caused by X-radiation. A danger arose in the isolation, treatment, and use of radioactive compounds in that radioactive substances could get inside the body. Methods were developed for measuring the activity of radioactive sources (the number of decays per second). These methods are the basis of radiometry.

The development and construction of nuclear reactors and charged particle accelerators, the development of nuclear power, and the mass production of radioactive isotopes have led to a great diversity of types of ionizing radiation and to the development of diverse dosimetric instruments (dosimeters).

Research on the biological effects of ionizing radiation on the cellular and molecular levels has brought about the development of microdosimetry, which examines the transfer of radiation energy to the microstructures of matter.