Present and future trends for neutron source calibrations at the National Institute of Standards and Technology

Abstract

The neutron source calibration facility operated by the United States National Institute of Standards and Technology (NIST) is a world-class calibration laboratory providing neutron source calibration services for radioisotopic sources with neutron emission rates ranging from 5 × 10 5 to 1 × 10 10 s −1. Calibrations are performed using the manganous sulfate bath technique with a relative expanded uncertainty of approximately 3.5% (2 σ). Recently, an improvement to the calibration procedure has been implemented whereby sources are regularly cross-calibrated against the national standard neutron source as well as one of three (international) standard sources formerly maintained by the Bureau International des Poids et Mesures. This feature helps ensure that the fidelity of NIST neutron source calibrations is maintained at the highest level. In addition to the Institute’s external customers, NIST’s neutron source calibration facility also provides important contributions to other neutron irradiation and calibration services provided by the Institute, as well as to NIST’s intramural research programs in neutron metrology, nuclear reactor pressure-vessel dosimetry, and fundamental neutron physics.