FISCHER FISCHERSCOPE X-RAY 5000 Series, Operator'S Manual

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FISCHERSCOPE
®
X-RAY 35
The Spectrum Window User Interface of the WinFTM Software
The higher the X-ray fluorescence energy of an element, the further to the right the corre-
sponding line will be in the spectrum.
According to Moseley’s Law, the energy increases as the atomic number of the respective
element increases, i.e., the lines of the “heavier” elements (those with a higher atomic
number) are further to the right in the spectrum.
The energy is measured in keV = kilo electron volts. 1 eV is the energy that an electron
gains as it moves through a field with a potential difference of 1 V.
5.8.4 Intensity
The intensity of a radiation is the amount of radiation that strikes a certain unit of area in
a specified time period.
In X-ray spectroscopy, the intensity of the radiation is measured as the count rate in
counts per second (cps).
Each peak in the spectrum corresponds to a relative maximum referenced to its
surrounding. This maximum correlates to the amount of radiating atoms of the corre-
sponding element.
The higher the peak, the more atoms of the respective element are present in the sample,
i.e., the higher the concentration of the respective element in the sample.
Thus, the intensity of the spectral line is a measure for the quantitative composition of the
sample.
Intensity: Dependency on the Coating Thickness
With coated samples, one generally sees the spectra of all coatings involved, their
elements as well as the spectrum of the substrate material where the coatings are depos-
ited. The intensity of the spectral lines of the coating material increases with an increase
in the coating thickness, because the number of the atoms in the coating increases, and
thus the intensity of the radiation of all atoms. At the same time, the radiation of the atoms
of coatings located under the top coating (buried coatings) and of the substrate material
decreases, because their spectral lines are absorbed to a greater degree, and thus weak-
ened, by the thicker top coating.
Intensity: Dependency on the Measurement Distance
The total intensity of the X-ray fluorescence radiation emitted by the specimen decreases
with the distance D of the detector from the sample with
1/D
2
, because the solid angle of
radiation collected by the detector decreases with an increase in the distance as well,
while the area of the radiation entry window of the detector remains the same.
For the coating thickness of a sample to be computed correctly, the distance D is auto-
matically taken into account by the evaluation software.