Generation of electrons, artificially or by radioactive decay.

See also Pair Production, Beta Radiation.

(INAA), see Neutron Activation Analysis.

An integral is a mathematical object that can be interpreted as an area or a generalization of an area. A number computed by a limiting process in which the domain of a function, often an interval or planar region, is divided into arbitrarily small units, the value of the function at a point in each unit is multiplied by the linear or areal measurement of that unit, and all such products are summed (summation in the limit). In CT, for example this mathematical function is used in the Fourier transformation.

An intensifying screen is used to intensify the x-ray effect during radiation exposure of the x-ray film. Approximately 5% of the x-ray photons will be absorbed by the film only. Intensifying screens consist of a sheet of inorganic salts that emits fluorescent light when stroked by x-rays. The fluorescent input and output screens of the image intensifier are very similar to intensifying screens.
Calcium tungstate and rare earths are two common salts (also called phosphors) used for intensifying screens. For example, a calcium tungstate (CaWo4) screen can absorb around 40% of the x-ray photons and convert the radiation into light photons. A basic feature of this screen types is related to the position of the k-edge on the energy axis. Tungsten (W) is a heavy element has a k-edge at 69.5 keV, while that for rare earth elements is in around 50 keV.
The fraction of x-rays absorbed by a screen is depending on the speed. Factors affecting the speed of a screen: Mammography cassettes contain usually one intensifying screen, but most others use two screens per film cassette. The intensifying screen as part of a film screen system has been an important component in radiology to reduce the radiation dose of the patient. Today, the conventional film cassette is being replaced by an imaging plate used in digital systems.

See also Actinides, Cinefluorography and Added Filtration.

In the internal conversion process the multipole electric field of the nucleus of an atom, in an electromagnetically excited state, react with an orbit electron. With enough energy the electron is ejected (internal conversion electron). The energy of the conversion electron depends on the energy transferred from the nucleus reduced by the shell specific binding energy. This process competes with gamma emission. The refilling for the vacancy left by the internal conversion electron occurs through the Auger effect, a higher orbit electron take place and x-ray or an Auger electron will be emitted.
The atomic number of the atom gets not changed by internal conversion.

See also Conversion Electron, Auger Effect and Auger Electron.