What is an element?

All matter (the tip of your nose, too) is formed of atoms. All atoms are formed of protons, neutrons and electrons. The number of protons in the atom defines the element. If matter consists of atoms similar to each other it is called an element (gold, oxygen or iron, for example). Notice that things usually contain many different elements.

What do we need for the analysis?

1. An object to be analysed, for example a ring

2. A source of radiation to excite the atoms.

3. As the excited atoms relax, so-called "characteristic radiation" is generated. We need the analyser to measure the energy of the quanta of the characteristic radiation and to count the number of quanta with different energies.

4. The elements and their percentages are defined by the computer according to the information of the analyser.

5. The printer and the monitor show the results.

6. People around the analyser are protected from radiation by lead glass and lead plates.

What is the exciting radiation like?

Protons and neutrons exist in the nucleus (centre) of an atom and electrons circulate the nucleus forming so called "electron shells". The shells are named with the letters: K, L, M, N, O,... starting from the middle. Matter that contains unstable atoms is called radioactive. When an atom decays, usually a part consisting of two protons and two neutrons (the nucleus of helium, alpha particle) separates from it and some gamma radiation is generated. The remaining part of the atom that is left has turned into another element (daughter). The gamma radiation excites the atoms hit by the gamma quanta. The movement of the alpha particle is stopped by air and it cannot excite the atoms of the object. In this analyser the exciters are the gamma quanta generated when the Americium atom (Am-241) decays. The daughter atom is Neptunium (Np-237).

Will the object still radiate after the measurement?

No, it won't.

How can the elements be seen in the printout?

The peaks of characteristic radiation of each element can be seen at their own places on the energy scale. However, the height or the area of the peaks are not directly proportional to the percentages of the elements.

Can the analyser make errors?

Yes, for example in the following cases:

1. The analyser does not show aluminium or lighter elements.

2. For example the needle of a silver brooch can be made of steel. The measurements are taken from a three centimetre circle in the middle of the chamber. If the needle is in that area, an error will occur because the analyser will measure the composition of the needle and not the brooch.

3. The object can be plated. It depends on the thickness of the plating whether the analyser can "see" under it. If it can, the results will always be false, because in this case even the element(s) of the plating won't be correct in the print-out.


This method is widely used in many industrial applications because it is very fast, it is non-destructive, and easy to use for on-line monitoring purposes in the field e.g. in metallurgy, in oil refineries, etc.



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