Abstract A water calorimeter was developed for conducting the absolute measurement of the absorbed dose to water of the photon beams from accelerator, followed by obtaining the international mutual recognition and establishing the primary standard for absorbed dose to water of the photo beams from accelerator and improving the dissemination for radiotherapy in China. The temperature drift of water phantom of the calorimeter was maintained at 0.5μ℃/s by the bath and Peltier cooling system. The resistance of thermistors caused by radiation was measured by Wheatstone AC bridge. After calibrating thermistors and the bridge separately,the absorbed dose to water of photon beams from accelerator was reproduced with the uncertainty of 0.30%. The key comparison on the absorbed dose to water of the photon beams from accelerator was performed between NIM and BIPM. By considering the result of NIM as against the reference quantity of BIPM, the ratio for the 6MV and 10MV photon beams is 0.9917 and 0.9949 respectively, which is within the acceptance of uncertainty.
WANG Kun,ZHANG Jian,WANG Zhi-peng, et al. Absolute Measurement and International Comparison of Absorbed Dose to Water for Accelerator Photon Beams by Water Calorimeter[J]. Acta Metrologica Sinica, 2020, 41(12): 1552-1558.
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2020, Vol. 41 
