4. Sensors using ionizing radiation

4.1 Measurement principles

X-rays and γ-rays are predominantly used, but applications are also being implemented with α or β-rays and even neutrons. Accelerated electron beams are also widely used. These different types of radiation are emitted either by radioactive elements or electron tubes.

To emit γ, α or β rays, sources are composed of radioelements, and many isotopes can be used. The energy of the radiation used is chosen according to the chemical compound to be measured and its thickness.

The emitters used are mainly iridium 192 (for checking steel parts from a few millimeters to 100 mm thick) and cobalt 60 (steel thicknesses from 30 to 200 mm). The decay of cobalt 60 produces particularly penetrating 1.33 MeV γ rays, with a half-life...