A bilateral comparison of standards for absorbed dose to water and air kerma of the Bundesamt für Eich- und Vermessungswesen (BEV), Austria, and of the Vinca Institute of Nuclear Sciences (VINS), Serbia, has been carried out. It was performed for air kerma and for absorbed dose to water in 60Co radiation beams and for air kerma in 137Cs radiation beams.
Transfer standards for air kerma and absorbed dose to water were exchanged by the participants. The participants determined the calibration coefficients of the transfer standards through comparison with their national standards in their respective 60Co and 137Cs beams.
The ratios of the calibration coefficients for the BEV and VINS transfer standards were calculated. The results were 0.9990 for absorbed dose to water in a 60Co beam at therapy level, 1.0004 for air kerma in a 60Co beam at therapy level, and 0.9926 for air kerma in a 137Cs beam at radiation protection level.
A connection to the key comparison data base (KCDB) is given as the results are linked to the key comparisons between the BEV and the Bureau International des Poids et Mesures (BIPM) in 2009. Detailed uncertainty budgets and graphical presentations are also included.
The project has been registered in the BIPM key Comparison Data Base (KCDB) as three different comparisons:
– EURAMET.RI(I)-K1.2: Air Kerma measured in 60Co radiation beams
– EURAMET.RI(I)-K4.2: Absorbed Dose to Water measured in 60Co radiation beams
– EURAMET.RI(I)-K5.1: Air Kerma measured in 137Cs radiation beams
KEY WORDS FOR SEARCH
Dosimetry, comparison, air kerma, absorbed dose to water, Austria, Serbia, EURAMET, ionizing radiation, CIPM MRA, BIPM KCDB
Main text
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
The graphite calorimeter of the Federal Office of Metrology and Surveying (BEV-Bundesamt für Eich- und Vermessungswesen) was established in the 1980s as the primary standard for the absorbed dose to water for (60)Co gamma ray beams. To maintain the primary standard at an international level the graphite calorimeter and its corresponding components had to undergo a refurbishment and modernisation process. The correction factors of the graphite calorimeter were re-evaluated with Monte Carlo and experimental methods to obtain improved values. These are the correction for the effect of the gaps (1.0061), the scaling correction (0.9998), the correction for the difference in air attenuation (0.9971) and the corrections for the effective measurement depths in the graphite phantom for the graphite calorimeter (0.9886) and the CC01-105 ionisation chamber (0.9913). Consequently, it was necessary to change the reference value for the absorbed dose rate to water of the (60)Co teletherapy unit used for the calibration of secondary standard dosemeters.
A comparison of the standards for air kerma of the National Institute of Metrology of China and of the Bureau International des Poids et Mesures was carried out in 60 Co gamma radiation at the BIPM in December 2001. The ratio of the NIM and the BIPM standards for air kerma is 0.9992, with a combined standard uncertainty of 0.0018.The degrees of equivalence between the NIM and the other participants in the ongoing key comparison BIPM.RI(I)-K1 have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given.
Main text
A new key comparison of the standards for air kerma of the Bundesamt f¨r Eich- und Vermessungswesen (BEV), Austria and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in July 2020. The comparison result, evaluated as a ratio of the BEV and the BIPM standards for air kerma, is 1.0030 with a combined standard uncertainty of 2.5 parts in 103. The result agrees within the uncertainties with the direct comparison carried out in 2009. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database.
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.
The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
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