Cecilia Kessler

Re-evaluation of the BIPM international standard for air kerma in 60Co gamma radiation

A re-evaluation of the BIPM standard for air kerma in 60Co radiation has been made. The changes to the air-kerma rate determination arise from four sources: (i) the results of Monte Carlo calculations of correction factors for the standard; (ii) a re-evaluation of the correction factor for saturation; (iii) a new evaluation of the air volume of the standard using an experimental chamber of variable volume; (iv) the adoption of a new reference beam at the BIPM. The combined effect of these changes is an increase in the BIPM determination of air-kerma rate by the factor 1.0054 and a reduction of the relative standard uncertainty of this determination to 1.5 parts in 103. A full uncertainty budget is presented. The new standard is effective from 1 November 2007.

Re-evaluation of the BIPM international standards for air kerma in x-rays

A re-evaluation of the BIPM standards for air kerma in low- and medium-energy x-rays has been made. The changes to the air-kerma rate determination arise from three sources: (i) the results of Monte Carlo calculations of diaphragm correction factors for the standards, (ii) a measurement of the effect of scatter from the diaphragm support and (iii) a re-evaluation of the electron-loss corrections for the medium-energy standard. Scatter from the diaphragm support explains a long-standing trend observed in the results of international comparisons for medium-energy x-rays. The new standards were implemented on 1 September 2009.

Re-evaluation of the BIPM standard for air kerma in 137Cs gamma radiation

Following the change to the BIPM standard for air kerma in 60Co adopted in November 2007, a re-evaluation of the BIPM standard for air kerma in 137Cs radiation has been made. The changes to the air-kerma rate determination arise from three sources: (i) the results of Monte Carlo calculations of correction factors for the standard; (ii) a re-evaluation of the correction factor for saturation; (iii) a new evaluation of the air volume of the standard using an experimental chamber of variable volume. The combined effect of these changes is an increase in the BIPM determination of the air-kerma rate by the factor 1.0030 and a reduction in the relative standard uncertainty of this determination to 1.9 parts in 103. A full uncertainty budget is presented.

Comparison of the standards for absorbed dose to water of the NPL, United Kingdom and the BIPM for60Co γ rays

A 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) has been made in 60Co gamma radiation under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result, based on the calibration coefficients for two transfer standards and expressed as a ratio of the NPL and the BIPM standards for absorbed dose to water, is 0.9980 (0.0064). The degrees of equivalence for the NPL and the other participants in this comparison have been calculated and the results are given in the form of a table for the eleven national metrology institutes (NMIs) that have taken part in the ongoing comparison for absorbed dose to water. A graphical presentation is also given. 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 Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the ENEA, Italy and the BIPM in medium-energy x-rays

A key comparison has been made between the air-kerma standards of the ENEA, Italy and the BIPM in the medium-energy x-ray range. The results show the standards to be in general agreement at the level of the expanded uncertainty (k = 2) of the comparison of 6.2 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. 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).

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the ENEA-INMRI, Italy and the BIPM in mammography x-rays

A first key comparison has been made between the air-kerma standards of the ENEA-INMRI, Italy and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the standard uncertainty for the comparison of 4.8 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.