Precision determination of absolute neutron flux. (8th June 2018)

• Record Type: Journal Article
• Authors: Yue, A T; Anderson, E S; Dewey, M S; Gilliam, D M; Greene, G L; Laptev, A B; Nico, J S; Snow, W M
• Is Part Of: Metrologia. Volume 55:Number 4(2018:Aug.)
• Page Start: 460
• Page End: 485
• Publication Date: 2018-06-08
• Subjects: alpha counting -- absolute neutron counting -- cold neutron -- neutron beam -- neutron metrology -- neutron wavelength; Weights and measures -- Periodicals; Weights and Measures -- Periodicals; 530.805
• DOI: 10.1088/1681-7575/aac283
• Languages: English
• ISSNs: 0026-1394

Abstract

Abstract: A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10 B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10 B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performed to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6 Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We also describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.