Determination of the absorbed dose to water for high-energy photons and electrons by total absorption of electrons in ferrous sulphate solution

Abstract

An arrangement is described for determining the relation between the energy imparted to ferrous sulphate (Fricke) solution by total absorption of 5.6 MeV electrons and the yield of ferric ions produced in the solution. Since the energy imparted is derived from measurements of basic quantities, the method represents an absolute determination of the absorbed dose to water. By means of ampoules filled with calibrated Fricke solution the beam of a cobalt source was measured to serve as a PTB standard for the quantity absorbed dose to water under specified conditions. The total uncertainty of this method of determining the absorbed dose to water for electrons and photons in the energy range above 1 MeV appears to be smaller than that of the calorimetric method, which is also applied in the author's laboratory for photon radiation.