An accelerator uses electrostatic or electromagnetic fields to increase the kinetic energy of charged particles (see alpha particle, beta particle) in order to produce ionization or a nuclear reaction in a target.
Accelerators (see cyclotron, linear accelerator) are used for the production of radionuclides (see Fluorine-18, Molybdenum, Technetium-99m) or directly for radiation therapy. Accelerator-produced radioactive material (ARM) is any radioactive substance that is produced by a particle accelerator. The accelerators used for radiation therapy generate gamma rays (also called Bremsstrahlung) with continuous energy by collision of high energy electrons on materials with high density (also referred as 'high z' - chemical elements with a high atomic number (Z)).
Electron accelerators with energies above 10 MeV can also produce neutrons induced by photons in the accelerator head material (mainly caused by photo nuclear reaction).

Decay chain or decay series is a series of decays that certain radioisotopes go through before reaching a stable form. For example, the production of technetium-99m (daughter nuclide with a half-life of 6 hours) from molybdenum-99 (parent nuclide with a half-life of 66 hours) in a generator is part of a decay chain.

See also Decay and Generator.

A generator is used in nuclear medicine to provide a radioisotope used for a scintigraphic procedure. A generator contains a radionuclide (e.g. molybdenum) that decays to another radionuclide (decay product, e.g. technetium) that can be extracted and used. The original radionuclide is firmly bound in the generator and remains behind.

See also Eluate