Fluence and absorbed dose in high energy electron beams.

The depth dependence of fluence, vectorial and planar fluence, energy fluence, vectorial and planar energy fluence and absorbed dose has been calculated in 5 and 20 MeV electron beams in water. The shape of these distributions has been compared with analytic expressions for fluence and absorbed dose and the general mechanisms governing the shape of the depth dose curve have been explained. In particular it is demonstrated that the depth dependence of planar energy fluence and mean energy is very similar, and so is the case for fluence and absorbed dose and primary fluence and absorbed dose from primaries with inclusion of fast secondaries. The results are useful for dosimetry and dose planning in high energy electron beams.