Glossary

Definitions in this glossary are meant for facilitating the use of the ANGLE 4 User Guide, often simplified, and may vary from the exact meanings.

absolute method – quantification based on calculations only, implying physical parameters which characterize the detection process

absorbing layers – all absorbing materials between the source and the detector (including air)

amplifier – piece of electronics further amplifying the signal from a preamplifier

antimicrophonic shield – in some detectors, thin layer of low-Z material between the end-cap and the crystal, aimed at absorbing noise (mechanical vibrations) which disturbs the spectrum at low energies

attenuation – decrease in the intensity of a photon beam due to interaction with matter

calculation parameters – in Angle, this data is needed for an efficiency calculation to be performed, including those for: detector, radioactive source and its container, counting geometry, gamma-energies of interest, reference efficiency curve and calculation precision.

calibration source – source with certified (specific) activities of the radionuclides present

coating layer – thin protective layer coating/lining the detector end-cap or source container

container foot – on some source containers, a small separation between the container bottom and the ground

counting arrangement – ensemble of the detector, source, container, holder and absorbing layers

counting geometry – see geometry

detection efficiency – characteristic of the counting arrangement: probability that a photon emitted from the sample will be detected/recorded by the detector

detector – device for radiation detection

detector bulletization – rounding of the detector crystal edges in order to smooth out the electric field in the crystal, enabling better charge collection

detector calibration – experimental determination of the detection efficiency using calibration source(s)

detector contact – electric contacts (electrodes) placed at the detector crystal, creating electric field therein; one of the contacts is normally the detector dead layer itself, the other may be, for example, a thin metal layer

detector crystal – active part of the detector, placed under high voltage and giving out the initial pulse from the energy deposited by the incoming photon

detector dead layer – inactive part of the detector crystal, usually at its surface

detector efficiency – characteristic of detector: detection efficiency at 1332 keV (Co-60 point source at 25 cm distance) as compared to 3 × 3" NaI detector (thus expressed in %); also called relative efficiency

detector end-cap – outer (visible) cap around the detector crystal, vacuum sealed

detector housing – inner physical support for the detector crystal

effective solid angle – compound parameter, closely related to detection efficiency, combining geometrical solid angle, attenuation effects and detection effects

emission probability – probability that an atomic nucleus will emit radiation (e.g. gamma-ray) in unit time,

end-cap window – a portion at the top of the detector end-cap, which is made of lower Z material than the end-cap itself (e.g. beryllium or carbon fiber, while the end-cap is usually made of aluminium or magnesium)

full-energy peak – part of the spectrum around characteristic gamma-energy for the given radionuclide

gamma-rays – photons emitted from atomic nucleus; gamma-energies range (at the low end) partially overlaps with X-rays range (at the high end)

gamma-spectrometry – quantitative determination of radionuclides present in the sample

gamma-spectroscopy – qualitative determination of radionuclides present in the sample

gamma-spectrum – result of spectroscopic measurement, distribution of recorded counts vs gamma-energies

GammaVision/Maestro – ORTEC’s spectroscopy software

Gauss coefficient – number of integration segments in the Gauss-Legendre numerical integration method; higher coefficient yields better calculation precision, but slower calculations

Genie 2000 (Genie 2K) – Canberra’s spectroscopy software

geometry (counting geometry) – in Angle this denotes the position of the source vs. the detector, including source holder and absorbing layers

holder (source support) – something that keeps the source at certain position vs the detector during counting

absorbing layers – all absorbing materials between the source and the detector (including air)

intercepting layers – see absorbing layers

Marinelli container (beaker) – source container in a form which enables the source to be closely positioned around the detector, yielding high detection efficiency

multichannel analyzer – piece of electronics where signals are sorted according to their intensity, which is proportional to the photon energy deposited in the crystal

peak area – net number of counts in the peak (i.e. with spectrum background subtracted)

peak efficiency – detection efficiency, taking into account only full deposition of photon energy in the detector

photon – the quantum of electromagnetic radiation, having the properties of both the particles and waves (including gamma and X-rays)

preamplifier – piece of electronics which performs initial amplification of the signal/charge obtained from the photon

quantification – step from qualitative to quantitative results

quasi-relative method – a semi-empirical method in which counting arrangements for the sample and the source are not exactly the same (as is the case for the relative method), but the difference is not great

radioactivity – spontaneous, probability-related (stochastic), transformation of atomic nucleus, followed by the emission of radiation (e.g. in the form of alpha, beta or gamma-rays)

radionuclide – atomic nucleus which is radioactive

reference efficiency curve – result of detector calibration, detection efficiency vs energy for the given counting arrangement and calibration source(s), in Angle, serves as a reference parameter for calculated efficiencies

relative method – quantification based on standards (sources with a known activity)

sample – source of unknown activity (which is to be determined)

scintillation detector – device for photon detection, having a scintillator crystal (usually NaI) as an active body

self-attenuation – attenuation of photon beams within the source itself

self-standing source – solid source (e.g. in the form of a pill) which can stand on the holder on its own (i.e. without a container)

semiconductor detector – device for photon detection, having a semiconductor crystal as an active body, usually high-purity germanium (HPGe)

semi-empirical method – quantification based partly on standards, partly on calculations

source – radioactive material

specific activity – activity per mass unit

spectrometer – a device used to register and analyze gamma-rays emitted from the source in a specific range of energies; gamma-energies range (its low end) partially overlaps with X-rays range (its high end), roughly at 20 – 100 keV

spectrometry – see gamma-spectrometry

spectroscopy – see gamma-spectroscopy

standard – source with known/certified activity, usually from a specialized manufacturer

total efficiency – detection efficiency, taking into account any (full or partial) deposition of photon energy in the detector

true coincidence summing – for some radionuclides, the effect of removal or pile-up of counts in a full-energy peak in the spectrum, due to simultaneous/cascade emission of photons in the decay schemes

vacuum (detector vacuum) – vacuum space between the crystal and end-cap

X-rays – photons emitted from atomic electron shell; range of X-rays (its high end) partially overlaps with range of gamma-energies (its low end), roughly at 20 – 100 keV