Any source of radiation capable of producing vacancies in the shells of an atom can be used as an excitation source for X-ray fluorescence (XRF). Without it, we could not have a precise, accurate gold tester and other forms of elemental analysis. It is, however, necessary to use a mono-energetic source in order to reduce unwanted background due to scatter occurring over a broad range of wavelengths, obscuring the fluorescence of interest. The commonly used sources for obtaining X-ray photon sources are X-ray tubes.
Special devices are used to make the X-ray beam from the conventional X-ray tube more monochromatic. This can be done through the use of transmission anode X-ray tubes, secondary fluorescents target or filters.
1. Transmission anode X-ray tubes operate on the principle that any metal is a good transmission filter for its own X-rays. It is a great aid in the production of fluorescence.
2. The anode material chosen so that it produces characteristic radiation of the desired energy. The accelerating potential chosen is such that the characteristic to bremsstrahlung the X-radiation is quite intense.
3. In secondary fluorescence, an X-ray beam from a primary X-ray tube is used to excite secondary fluorescence from a target, whose material is such that it produces the most appropriate exciting radiation.
4. Filters make use of a metal foil to isolate an almost mono-energetic excitation beam.
The XRF sources lay out the basic benefits because the sample can be used again and again for the same purpose due to the source compatibility with the sample. Many such analyses are there where the source induces the sample to be unable to be used.