Medin J, Ross C K, Stucki G, Klassen N V, Seuntjens J P
Ionizing Radiation Standards, Institute for National Measurement Standards, National Research Council, Ottawa, ON K1A 0R6, Canada.
Phys Med Biol. 2004 Sep 7;49(17):4073-86. doi: 10.1088/0031-9155/49/17/017.
As part of a collaborative project between the National Research Council of Canada (NRC) and the Swiss Federal Office of Metrology and Accreditation (METAS), a sealed water calorimeter was built at NRC and transferred to METAS. The calorimeter is operated at 4 degrees C and uses two thermistor probes in a sealed glass vessel containing high-purity water to measure the radiation-induced temperature rise. The various correction factors have been evaluated and the estimated standard uncertainty on the absorbed dose to water is 0.41%. An extensive set of measurements using 60Co gamma-rays was carried out at NRC and two ionization chambers were calibrated against the absorbed dose determined calorimetrically. The chambers were also calibrated against the NRC standard for absorbed dose. After transferring the calorimeter to METAS, a similar set of measurements was carried out using their 60Co beam and the same two ionization chambers were calibrated against the absorbed dose to water established at METAS. The discrepancy between the three sets of calibration coefficients was smaller than the estimated standard uncertainty of 0.47% on the ratio of any pair of calibration coefficients.
作为加拿大国家研究委员会（NRC）与瑞士联邦计量与认证办公室（METAS）合作项目的一部分，一台密封水热计在NRC制造并转移至METAS。该热计在4摄氏度下运行，在一个装有高纯水的密封玻璃容器中使用两个热敏电阻探头来测量辐射引起的温度升高。已评估了各种校正因子，水吸收剂量的估计标准不确定度为0.41%。在NRC使用60Co伽马射线进行了一系列广泛的测量，并根据量热法确定的吸收剂量对两个电离室进行了校准。这些电离室还根据NRC的吸收剂量标准进行了校准。将热计转移到METAS后，使用他们的60Co束进行了类似的一组测量，并根据METAS确定的水吸收剂量对相同的两个电离室进行了校准。三组校准系数之间的差异小于任何一对校准系数比值的估计标准不确定度0.47%。
