CIPM MRA COMPARISON REPORTS

A new key comparison of the standards for absorbed dose to water of the National Physical Laboratory (NPL), United Kingdom, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the ⁶⁰Co radiation beam of the BIPM in September 2025. The comparison result, based on the calibration coefficients for two transfer chambers and evaluated as a ratio of the NPL and the BIPM standards for absorbed dose to water, is 0.9998 with a combined standard uncertainty of 6.7 parts in 10³. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database.

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).