Understanding Neutron Radiography Post Exam Reading VIII-Part 2a of 2A

PART 2. Ion Chambers and Proportional
Counters
Principles of Ionization
The mechanism most widely used in radiation survey applications is the
ionization principle: charged particles producing ion pairs by direct interaction.
These charged particles may (1) collide with electrons and remove them from
their atoms or (2) transfer energy to an electron by the interaction of their
electric fields (Fig. 1). If the energy transfer is not sufficient to completely
remove an electron, the atom is left in a disturbed or excited state.
Gamma and X-ray photons interact with matter mainly by:
■ photoelectric absorption,
■ compton scattering and
■ pair production,
each of which produces electrons and ions that may be collected and
measured.
Charlie Chong/ Fion Zhang