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|  Radiological Assessor Training
DOE-HDBK-1141-2001
Student's Guide
IV. Analytical x-ray machines
A. Fluorescence analysis
Characteristic x-rays that result from ionization of
atoms can be used to identify atoms, since the
characteristic x-rays will have energies that are
unique to that element. This forms the basis for
x-ray fluorescence spectroscopy. A sample to
be analyzed is irradiated by a beam of high-
intensity x-rays. The x-rays ionize atoms in the
sample, which emit characteristic x-rays when
the electron shell vacancies created by
ionization are filled.
The characteristic x-rays can be analyzed by
determining their energy, or by determining their
wavelength. Either way, the result leads to
information about the elemental composition of
the sample.
These instruments are usually completely
enclosed. Access doors are provided for
changing samples, and the doors are equipped
with interlocks to prevent access to the x-ray
beam.
The hazard is primarily an external dose hazard
to scattered radiation from the components and
the sample, and is typically fairly low.
B. X-ray diffraction
When x-rays are scattered by a crystalline solid,
they are scattered from the different atoms, but
only in certain directions. This technique is used
for crystal structure research.
The primary beam and the diffracted beams are
very small and well collimated. In some types of
diffraction equipment, the sample cannot be
enclosed in a structure. The primary beam is
controlled by a shutter that opens and closes.
The major hazard associated with diffraction
units is intense, localized exposure from the
Module 12 - 5
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