First a little history (you can skip this paragraph): The term spectrometry is composed of the parts spec- and -metry. The Greek word skopein means "to see" or "to look". This root has become "spec" in Latin. The suffix -metry (from ancient Greek μέτρον meaning "measure, measure standard") literally means that something is measured. Therefore, the term spectrometry can be interpreted as the measurement and visual representation of the result.
This leads to the following definition:
Spectrometry is the practical application where results are generated. In our case, the measurement of the intensity of gamma radiation with an appropriate measuring device.
Spectrum of a low-pressure mercury vapor lamp, recorded with a 256-pixel line sensor or with a camera (Ref.: https://en.wikipedia.org/wiki/Spectroscopy).
Good, but what do we do now with this definition in the case of gamma spectrometry?
Let's repeat what we already know:
If we can determine (i.e., measure) the energy of gamma radiation, then we can identify the radioactive isotope that emitted this gamma radiation during its radioactive decay.
And this is exactly the procedure carried out in gamma spectrometry:
- We measure the energy of the gamma radiation with an appropriate measuring system,
- visualize the measurement result,
- evaluate the measurement result, and
- identify the isotope that emitted the gamma radiation.
Note:
The list can be supplemented with the point quantification, meaning how much of an isotope is present. However, we will only address this point in the section Advanced.
With the four points of the list, we will address the next pages. We will investigate how we can measure the energies of gamma radiation and how we can process the measurement results so that we can ultimately identify the isotopes.
But let's take a small interlude at this point to clarify a sometimes occurring confusion of terms:
In the literature, the terms gamma spectrometry and gamma spectroscopy are often found. Here,
- gamma spectroscopy refers to a qualitative measurement used for the identification of existing radionuclides, and
- gamma spectrometry refers to the quantitative determination of the activity of a radionuclide (including the measurement).
Note:
In practice, these designations are often not used clearly. For example, gamma detectors are sometimes also referred to as gamma spectrometers, although the correct designation should be gamma spectroscope.
Now we need to discuss how gamma radiation is measured.
