Key comparison BIPM.RI(I)-K4 of the absorbed dose to water standards in ⁶⁰Co gamma radiation beams of the NIST, USA and of the BIPM

Main text A new key comparison of the standards for absorbed dose to water of the National Institute of Standards and Technology (NIST), USA, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60 Co radiation beam of the BIPM in October 2023. The comparison result, based on the calibration coefficients for two transfer standards and evaluated as a ratio of the NIST and the BIPM standards for absorbed dose to water, is 1.0019 with a combined standard uncertainty of 5.7 parts in 10 3 . 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 https://www.bipm.org/kcdb/ . 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).