AN EXPERIMENTAL-METHOD FOR DETERMINING THE HEAT DEFECT OF WATER USING TOTAL ABSORPTION OF HIGH-ENERGY ELECTRONS

The experimental procedure described here in detail enables the heat defect of water caused by electron radiation in the energy range from 1 MeV to 5 MeV to be determined with an overall uncertainty of less than 0,5 % for the correction factor. The principle of measurement is based on a comparison of the temperature increase caused by the radiation energy of electrons totally absorbed in water with that caused by an ohmic heating of the water. In measuring the radiant energy of the electrons, corrections are needed for backscatter of the electrons entering the water and for bremsstrahlung energy loss during electron slowing down. Precise knowledge of the heat defect is a prerequisite for the establishment of the water absorbed-dose calorimeter as a primary standard of absorbed dose to water.