Appendix B
Terms Used in Text
Absorption.A process by which the total energy of a radiation is removed
by an absorber through which it passes.
Accelerator.A machine to accelerate charged particles linearly or in circu-
lar paths by means of an electromagnetic field. The accelerated particles
such as a-particles, protons, deuterons, and heavy ions possess high ener-
gies and can cause nuclear reactions in target atoms by irradiation.
Accuracy.A term used to indicate how close a measurement of a quantity
is to its true value.
Annihilation radiation.g-Radiations of 511 keV energy emitted at 180°
after a b+-particle is annihilated by combining with an electron in matter.
Atomic mass unit (amu).By definition, one twelfth of the mass of^126 C, equal
to 1.66 × 10 −^24 g or 931 MeV.
Atomic number (Z).The number of protons in the nucleus of an atom.
Attenuation.A process by which the intensity of radiation is reduced by
absorption and/or scattering during its passage through matter.
Attenuation coefficient.The fraction of g-ray energy attenuated (absorbed
plus scattered) per unit length of an absorber (linear attenuation
coefficient,m) or per gram of an absorber (mass attenuation coefficient,
mm).
Auger electron.An electron ejected from an energy shell, instead of a char-
acteristic x-ray emission, carrying the energy equal to that of the x-ray
minus its binding energy.
Average life (t). SeeMean life.
Avogadro’s number.The number of molecules in 1 g · mole of any substance
or the number of atoms in 1 g · atom of any element. It is equal to 6.02 ×
1023.
Becquerel (Bq).A unit of radioactivity. One becquerel is equal to 1 disin-
tegration per second.
Binding energy.The energy to bind two entities together. In a nucleus, it is
the energy needed to separate a nucleon completely from other nucle-
ons in the nucleus. In a chemical bond, it is the energy necessary to sep-
arate two binding partners an infinite distance.
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