4. Radioactive signal detection

Detection must be adapted to the type of radiation emitted by the tracer:

• electromagnetic radiation (γ, X): iodine 125, cobalt 57 ;

• particulate radiation β ^– soft (tritium, carbon 14) and β ^– hard (phosphorus 32, sulfur 35).

To detect and quantify high-energy electromagnetic (γ, X) or particulate β ^– radiation, we use a probe consisting of a solid scintillator and a photosensitive cell, together forming the photomultiplier. In the case of very low-energy particle radiation (e.g. tritium, carbon 14), the scintillator is liquid, so that it is in contact with the radioactive source.