G

gain (of an amplifier)

ratio of output pulse height to input pulse height

Ga

atomic symbol for gallium

gamma decay

mode of nuclear decay in which a nucleus emits a gamma-ray, leaving its atomic number and mass number unchanged but making a transition to a lower energy state

gamma-emitter

gamma-emitting radionuclide

gamma-emitting

capable of undergoing gamma decay

gamma radiation

radiation consisting of gamma-rays

gamma-ray (γ-ray)

photon (typically high-energy) emitted from an atomic nucleus or from the annihilation of a particle and its antiparticle

gamma-ray spectrometry; gamma spectrometry

technique for identifying and quantifying radionuclides by measuring the spectrum of energies of their emitted gamma-rays (in conversation often called simply gamma spec)

gas amplification

process in which the ionization of gas caused by radiation in an ionization chamber is increased by the application of a sufficiently high voltage to the chamber electrodes

gas proportional counter (GPC)

radiation counter based on an ionization chamber where the voltage applied to the electrodes is in the proportional region — also called simply a proportional counter

gas flow proportional counter (GFPC)

gas proportional counter in which gas flows continuously through the ionization chamber

Gaussian

normally distributed, or shaped like the probability density function of a normal distribution

Gaussian distribution

normal distribution

Gd

atomic symbol for gadolinium

Ge

atomic symbol for germanium

Geiger-Müller counter

radiation counter based on an ionization chamber where the voltage applied to the electrodes is in the Geiger-Müller region

Geiger-Müller region

range of voltages that when applied to the electrodes of an ionization chamber are sufficient to maximize the gas amplification to the point where all ionizing events generate pulses of the same amplitude, regardless of the number of ion pairs initially produced

Ge(Li) detector; lithium-drifted germanium detector

gamma-ray detector whose principal component is a cryogenic crystal of lithium-drifted germanium

Note: A Ge(Li) detector must remain at an extremely low temperature even when not in use. Ge(Li) detectors have been almost com­pletely replaced now by high-purity germanium (HPGe) detectors.

geometry

1. spatial configuration of a radioactive source and radiation detector for a radia­tion measure­ment, which includes the size and shape of the source and its position and orienta­tion relative to the detector
2. configuration of a radioactive source and radia­tion detector for a radia­tion measure­ment, including the source’s size, shape, container, composition, density, and position and orienta­tion relative to the detector

geometry factor

mean value of the solid angle subtended by the sensitive portion of the radiation detector at all points of the radioactive source, divided by 4π

GM; G-M

Geiger-Müller

gravimetric

relating to measurement by weight or mass

gray (Gy)

special name for the SI derived unit of absorbed dose, equal to 1 J/kg

gross

1. before subtraction of background, tare, or other correction terms, as in gross count (cf. net)
2. lacking detail, as in gross alpha activity

gross alpha activity

mean rate of alpha decay in a quantity of material

gross beta activity

mean rate of beta decay in a quantity of material

gross count

total count recorded by a radiation counter during a measurement of a radioactive source (cf. net count)

gross count rate

gross count divided by the live time (cf. net count rate)

gross gamma activity

mean rate of gamma decay in a quantity of material

ground state

minimum-energy state of an atom, molecule, or atomic nucleus

GUM

Guide to the Expression of Uncertainty in Measurement