A comparison of ionization and ferrous sulphate dosimetry for megavoltage electrons

For 60Co gamma -radiation and electrons of incident energies from 3 to 35 MeV, dose measurements using ionization and FeSO4 methods are compared. If factors given by the HPA 'Practical guide to electron dosimetry' are used, results from the two methods do not differ by more than 4%. However, the ionization results based on the HPA values of CE give a mean G-value of 15.2 over this energy region. If it is assumed that photon beams producing primary electrons of a given mean energy have the same G-value as electrons of that energy, then electron G-values predicted from photon results using HPA Clambda values and the same FeSO4 equipment are about 8% higher than experimental values for 6 to 10 MeV electrons.