A comparison has been made of the air-kerma standards for low-energy x-rays at the National Institute of Standards and Technology (NIST) and the Physikalisch-Technische Bundesanstalt (PTB). The comparison involved a series of measurements at the PTB and the NIST using the air-kerma standards and two NIST reference-class transfer ionization chamber standards. Results are presented for the reference beam qualities in the range from 25 kV to 50 kV for the low energy x-rays, including the techniques used for mammography dose traceability. The tungsten generated reference radiation techniques between 25 kV to 50 kV used for this comparison are new to NIST; therefore this comparison will serve as the preliminary comparison for NIST and a verification of the primary standard correction factors. The mammography comparison will repeat two previously unpublished comparisons between PTB and NIST. The results show the standards to be in reasonable agreement within the standard uncertainty of the comparison of about 0.4 %.
Citation: Journal of Research (NIST JRES) -
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
air kerma, free-air ionizaton chamber, primary standards, reference radiation qualities, x-rays