Understanding Neutron Radiography Post Exam Reading VIII-Part 2a of 2A
Understanding Neutron Radiography Post Exam Reading VIII-Part 2a of 2A
Understanding Neutron Radiography Post Exam Reading VIII-Part 2a of 2A
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Sources <strong>of</strong> Attenuation<br />
The attenuation that results due to the interaction between penetrating<br />
radiation and matter is not a simple process. A single interaction event<br />
between a primary x-ray photon and a particle <strong>of</strong> matter does not usually<br />
result in the photon changing to some other form <strong>of</strong> energy and effectively<br />
disappearing. Several interaction events are usually involved and the total<br />
attenuation is the sum <strong>of</strong> the attenuation due to different types <strong>of</strong> interactions.<br />
These interactions include the photoelectric effect, scattering, and pair<br />
production. The figure below shows an approximation <strong>of</strong> the total absorption<br />
coefficient, (µ), in red, for iron plotted as a function <strong>of</strong> radiation energy.<br />
The four radiation-matter interactions that contribute to the total absorption<br />
are shown in black. The four types <strong>of</strong> interactions are: photoelectric (PE),<br />
Compton scattering (C), pair production (PP), and Thomson or Rayleigh<br />
scattering (R). Since most industrial radiography is done in the 0.1 to 1.5 MeV<br />
range, it can be seen from the plot that photoelectric and Compton scattering<br />
account for the majority <strong>of</strong> attenuation encountered.<br />
Charlie Chong/ Fion Zhang<br />
https://www.nde-ed.org/EducationResources/CommunityCollege/<strong>Radiography</strong>/Physics/attenuation.htm
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