CIANFLONE 2501XBT, Инструкция по эксплуатации и безопасности

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4. PRINCIPLE OF OPERATION
4-1
Source
Collimator
X
-R
a
y Tu
b
e
Specimen
Crystal
Detector
Collimator
Detector
Radiation Path
Image 4-1
The x-ray tube directs a beam of primary radiation onto a sample of the material
under analysis. The primary radiation causes the sample to emit a secondary
fluorescence radiation that contains a characteristic wavelength of each element
present in the sample. The characteristic line of each element represents a
wavelength, which varies in a regular fashion from one element to another. The
characteristic wavelengths decrease as the atomic number of the element increases.
The characteristic radiation from all of the elements present in the sample is directed
through the source or divergent collimator onto a large, single crystal. The
collimator, for the most part, eliminates divergence of the radiation so that a parallel
beam of radiation arrives at the crystal and detector. The crystal acts as a diffraction
grating, which separates the various wavelengths emitted by the elements in the
sample. This reflected radiation passes through a receiving or detector collimator
located in front of a gas-filled, sealed proportional detector.
The detector converts x-ray
photons into electrical pulses,
which are then amplified, sent
to the scaler and digital
display. The emitted long
wavelength radiation, such as
that emitted from Ti, V and
Cr, are dispersed at high
goniometer angles and short
wavelength radiation, such as
that emitted from Mo, Nb and
Zr, are dispersed at lower
goniometer angles.
By scanning through the
entire angular range with the
detector, the presence of
each element in the sample
can be detected by
determining the presence of
radiation at their
corresponding angular position.
The intensity of each wavelength is, with suitable corrections, proportional to the
amount of the corresponding element in the sample. Therefore, the intensity of
radiation at each element setting, gives an indication of: 1.) Whether or not the
element appears in the sample; 2.) How much of the element is present in the
sample.