Comparison of absorbed dose determinations between water and polystyrene-water calorimeters

The absorbed dose in water determined by a water calorimeter was compared with that determined by a polystyrene-water calorimeter. An ionisation chamber was also used in the absorbed dose determinations. The beams that were used were cobalt-60 gamma rays, and 10 and 25 MV X-ray photons. A nominal 18 MeV electron beam was also included in the study. Results indicate that the absorbed dose measured by the water calorimeter using once-deionised water is 1.4 to 3.6% higher than that by the polystyrene-water calorimeter, indicating an average of 2.5% exothermicity of water. This finding is similar to that in the literature.