Henri Becquerel demonstrated beta particles in 1900. Identical with electrons is there negative charge at -1. Their mass is 549 millionths of one AMU, 1/2000 of the mass of a proton or neutron. Beta particles consist of high energetic electrons emitted by radioactive nuclei or neutrons. By the process of beta decay, one of the neutrons in the nucleus is transformed into a proton and a new atom is formed which has one less neutron but one more proton in the core. Beta decay is accompanied by the emission of a positron (the antiparticle of the electron), a positive charged antineutrino. Beta particles have a greater range of penetration than alpha particles but less than gamma rays or x-rays. The name beta was coined by Rutherford in 1897. The traveling speed of beta particles depends on their energy. Because of their small mass and charge beta particles travel deep into tissues and cause cellular damage and possible cancer.

See also Radiation Shielding.

Charged particles (ions) range from lighter electrons and positrons to heavier alpha particle and other not neutral nuclei. The charge is measured in coulomb.

An ion is an atomic particle that is electrically charged, either negatively or positively by loss or addition of one or more electrons. The simplest ions are for example hydrogen ions (a proton, H+), or an alpha particle (helium ion, He2+).
Positively-charged ions have fewer electrons than protons. They are cations due to the attraction to cathodes.
Negatively charged ions have more electrons in the electron shells than they have protons in the core. Due to their attraction to anodes they are named anions.

Radiation can ionize matter caused by the high energy which displaces electrons during interactions with atoms. In the electromagnetic spectrum higher frequency ultraviolet radiation begins to have enough energy to ionize matter.
Examples of ionizing radiation include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions by direct or secondary processes in passage through tissues.
Damage of living tissue results from the transfer of energy to atoms and molecules in the cellular structure. Ionized cells have to repair themselves to remain alive. Generally, healthy cells have a higher capability to repair themselves than cancer cells.

Biological effects of ionizing radiation exposure:
Ionizing radiation are used in a wide range of facilities, including health care, research institutions, nuclear reactors and their support facilities, and other manufacturing settings. These radiation sources can pose a serious hazard to affected people and environment if not properly controlled.

See also Radiation Safety, Controlled Area, Radiotoxicity and As Low As Reasonably Achievable.

(NAA) Neutron activation analysis is a very sensitive analytical technique to determine even very low concentration of chemical elements, trace elements for example, in small biological samples.
NAA becomes commercial available in the USA in 1960.
In the activation process stable nuclides in the sample, which is placed in a neutron beam (neutron flux, 90-95% are thermal neutron with low energy levels under 0.5 eV), will change to radioactive nuclides through neutron capture (artificial radioactivity). These radioactive nuclides decay by emitting alpha-, beta-particles and gamma-rays with a unique half-life. Qualitative and quantitative analysis of the sample is done with a high-resolution gamma-ray spectrometer.
NAA is subdivided into the following techniques: