Testing of the code of practice at different electron energies and phantom materials

The aim of this investigation is to compare results of absorbed dose determinations in electron beams using methods based on measurements with plane parallel ionization chambers (TRS-381) and on the Fricke dosimetry. In order to exclude uncertainties in the air-kerma calibration of the reference cylindrical ionization chamber and in the εG-value of the Fricke dosimeter, dosimetry comparisons were made also using these two dosimetry systems in a 60Co beam. Assuming that the air-kerma calibration was correct and applying the interaction coefficients from TRS-381 would have given an εG of 352.4x10-6 m2 kg-1 Gy-1 which is in excellent agreement with published values. This indicates that the measurement procedure is reliable. Comparing dose determinations using the so called ''electron method'' from TRS-381 measuring with a NACP-02 chamber and using the Fricke method gave a ratio Dw,NACP/Dw,Fricke = 0.998 ± 0.003 (1SD) in the electron energy range, EZ from 3 to 36 MeV, thus showing that the procedures used from the TRS-381 agree closely with more direct methods (i.e. Fricke). It was shown that the uncertainty would increase if ionization chamber measurements were made in plastics. (author)