Methodology for the dissemination of megavoltage photon-beam calibrations from the IAEA Dosimetry Laboratory to SSDLs and end users

The IAEA Dosimetry Laboratory maintains a linear accelerator with a selection of five photon beam qualities in the range from 6 MV (TPR_20,10 = 0.665) to 18 MV (TPR_20,10 = 0.780). To obtain traceability for these beams reference-class ionization chambers belonging to the IAEA are calibrated at the BIPM in terms of absorbed dose to water for three photon-beam qualities spanning a marginally tighter range, from 6 MV (TPR_20,10 = 0.686) to 18 MV (TPR_20,10 = 0.774). Evidently, the BIPM qualities are not matched to those at the IAEA, nor will the latter in general match those of SSDLs to whom the IAEA might provide calibrated instruments for the purpose of providing traceability or for use in dosimetry audits.