CPB Ljubljana 2018 course book

Air Kerma-rate constant Γ δ

Let us consider a source of irradiation being a point in free space (vacuum) , an ideal point source , consisting of a specific radionuclide and having a activity A.

If is the air kerma rate due to photons of energy greater than a certain cut-off value  at a distance r from that point source, then the air kerma-rate constant Γ δ of that radionuclide is defined as:

If the unit gray (Gy) for the kerma and becquerel (Bq) for the activity are used, then the unit of the air kerma-rate constant is Gy.s -1 .Bq -1 .m² .