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Title: Precision determination of absolute neutron flux

Journal Article · · Metrologia
 [1];  [2];  [1];  [1];  [3]; ORCiD logo [4];  [1];  [2]
  1. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  2. Indiana Univ., Bloomington, IN (United States)
  3. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
+ Show Author Affiliations

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 10B-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 10B 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 6Li 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.

Research Organization:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC). Nuclear Physics (NP) (SC-26); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); National Science Foundation (NSF); USDOE
Grant/Contract Number:
AC52-06NA25396; SC0005925; FG02- 03ER41258; PHY-1306942; 70NANB14H299; AC05-00OR22725
OSTI ID:
1441345
Alternate ID(s):
OSTI ID: 1481658
Report Number(s):
LA-UR-18-20415
Journal Information:
Metrologia, Vol. 55, Issue 4; ISSN 0026-1394
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 4 works
Citation information provided by
Web of Science

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Cited By (1)

The neutron lifetime anomaly and charge exchange collisions of trapped protons journal June 2019

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Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
alpha counting
absolute neutron counting
cold neutron
neutron beam
neutron wavelength