Technical Aspects of the NIST Proficiency Tests during the Accreditation Process
R.M. Minniti (NIST)
The Radiation Interactions and Dosimetry group at the National Institute of Standards and Technology (NIST) conducts proficiency tests for air-kerma calibrations for laboratories typically that are interested in seeking accreditation through several of the existing accreditation bodies within the US. Results of a proficiency test are used by accreditation bodies to evaluate the ability of the facility under test to transfer a measurement of air kerma and to provide NIST traceability. The NIST proficiency test protocol involves sending a NIST reference-class ionization chamber to the facility under test. The participant calibrates the ionization chamber using their appropriate NIST-equivalent beam quality(s), and the chamber is returned to NIST or to the next participating facility if the test involves multiple participants. The participant provides NIST with the calibration coefficient(s) for the NIST chamber determined at their facility in units of Gy/C for a given beam quality. The chamber is re-calibrated upon arrival at NIST, to ensure that no damage occurred while in transit. The comparative results are then included in a proficiency-test report issued upon the completion of the test. The results reveal the degree to which the participating calibration facility can demonstrate proficiency in transferring a NIST air-kerma calibration under the conditions of the facility at the time of the proficiency test.