Comparison of national air kerma standards for ISO 4037 narrow spectrum series in the range 30 kV to 300 kV

For the first time results are presented of an indirect comparison of ten national standards for air kerma for ten radiation qualities of the ISO 4037 narrow spectrum series in the range from 30 kV to 300 kV. Nine of the ten participants maintain primary air kerma standards, one is traceable to PTB. The comparison was conducted in the time period from February 2004 until October 2005. For each radiation quality, the results are analysed in terms of the degrees of equivalence of each national standard with respect to the comparison reference value. These data form the basis of the results in the BIPM key comparison database for comparison EUROMET.RI(I)-S3. In addition, results are presented of differences in the results due to different realizations of beam qualities at the participants' sites and of the influence of different transfer chamber sizes on the variance of the comparison results.