CPB Ljubljana 2018 course book

Exposure X and Air Kerma K α

When the volume element dV in the radiation field is filled by air then we have the air kerma, K α .

Then the following relationship between exposure X and air kerma K α

exists

dm dQ

X 

= . .

e -

air

−

dE

tr

K



dm=ρ

.dV

α

dm

e is the elementary charge and W is the mean energy expended in air per ion pair formed, W/e = 33.97 J.C -1 . , the fraction of the energy of the electrons liberated by photons in air that lost to radiative processes (bremsstrahlung and fluorescence, g α < 0.3% for E  1MeV). Is the mean value of g α

g

a