 [G]- G See G-value.
- GAIN (MULTIPLIER TUBE) Ratio of output to input electrical power. NM.
- GAMMA CASCADE Two or more different gamma rays emitted successively, that is, in coincidence , as a single nucleus passes through one or more energy levels.
- GAMMA QUANTUM A photon , a single unit of electromagnetic radiation , usually nuclear in origin.
- GAMMA RADIATION Electromagnetic radiation emitted in the process of nuclear transformation or particle annihilation.
- GAMMA RADIATION, CAPTURE See capture gamma radiation.
- GAMMA-RAY SPECTROMETER A system for determining the energy spectrum of gamma rays.
- GAMMA-RAY SPECTROMETER, ANTI-COMPTON A gamma-ray spectrometer in which the effect of the Compton scattering is at least partly compensated by an anticoincidence requirement on the full energy peak.
- GAMMA-RAY SPECTRUM A spectrum of photon radiation.
- GAMOW BARRIER The potential barrier which retards the escape of alpha-particles from the nucleus. M.
- GAS JET A gas transport system using a stream of helium gas to thermalize and very rapidly transport recoil products from nuclear reactions to a collector and detection apparatus.
- GAS-FLOW COUNTER A proportional counter tube in which the gas between the cathode and anode is constantly, but slowly, replenished through flow.
- GAS-TRANSPORT SYSTEM See gas jet.
 GEIGER-M?LLER COUNTER TUBE See counter tube, Geiger-M¸ller.- GEIGER-M?LLER REGION The range of operating voltage of a counter tube in which each ionizing event gives rise to an output pulse having an amplitude independent of the number of ions initially produced in the sensitive volume by that ionizing event.
- GEIGER-M?LLER THRESHOLD The minimum voltage necessary for a counter tube to operate in the Geiger-M¸ller region.
- GENERATOR See radioisotope generator.
- GENETIC RELATION A reference to the connection between two nuclides which are members of the same decay chain.
- GEOMETRIC ATTENUATION The reduction of radiation due only to the effect of the distance between the point of interest and the source, excluding the effect of any matter present.
- GEOMETRY (, COUNTING) A term used colloquially to signify the arrangement in space of the various components in an experiment, particularly the source and the detector in radiation measurements.
- GEOMETRY FACTOR The average solid angle in steradians at the source subtended by the aperture or sensitive volume of the detector , divided by 4.
- GERMANIUM DETECTOR A diffused junction semiconductor detector in which germanium is the base solid state material.
- GERMANIUM DETECTOR, Ge(Li) A diffused junction semiconductor detector into which lithium has been diffused from the surface and which must be maintained at low (liquid nitrogen) temperatures. It is used in high resolution gamma ray spectrometry. NAC.
- GERMANIUM DETECTOR, HIGH PURITY A semiconductor detector of ultrahigh purity, usually referred to as intrinsic germanium. The detector is used for high resolution gamma ray spectroscopy and must be operated at low (liquid nitrogen) temperatures to reduce leakage noise but need not be otherwise maintained at low temperatures. NAC.
- GERMANIUM DETECTOR, INTRINSIC See germanium detector, high purity. GLOVE BOX An enclosure in which material may be manipulated in isolation from the operator's environment. This manipulation is effected by gauntlet gloves or flexible plastic devices fixed to ports in the walls of the box.
- GM COUNTER See counter tube, Geiger-M¸ller.
- GRAIN YIELD The average number of silver grains per electron strike on the recording layer of autoradiography film. J.
- GRANDDAUGHTER In a sequence of radioactive decays , the daughter of the daughter.
- GRAY SI unit of absorbed dose ; 1 gray = 1 joule/kilogram.
- GRENZ RAYS X-rays produced in the region of 5 to 20 kV. NM.
- GROUND STATE The state of lowest energy of a system.
- GROUP PRECONCENTRATION An operation (process) as a result of which several components are isolated in one step. This may be achieved in one of two ways: by transport either of the matrix or of the microcomponents into a second phase. C.
- GROUP SEPARATION See group preconcentration.
- GROWTH AND DECAY CURVE A graph showing the relative amount of radioactivity remaining after any time interval and in which the radioactivity also shows growth from a parent nuclide.
- GROWTH CURVE (OF ACTIVITY) Curve giving the activity of a radioactive nuclide as a function of time and showing the increase of the activity through the decay of the parent substance or as a result of activation.
- GUARD FOIL In an irradiation of a target, a foil that is used on one side of that target to exactly compensate for nuclear reaction products that recoil out of the opposite side and are otherwise lost.
- G-VALUE The number of specified chemical events produced in an irradiated substance per eV of energy absorbed from ionizing radiation.
- Gy Symbol for the absorbed dose unit gray. Not to be confused with an old notation for gigayear, also Gy, but now Ga Planck's constant, h , divided by 2p.
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