Precision Cross Section Measurements of Prompt Gamma-Ray Production by 14.1 MeV Neutrons
A new method has been developed to measure the prompt γ-ray production cross section with the accuracy of 4.98% using Associated Particle Neutron Elemental Imaging (APNEI) technique. A completely operational experimental platform including an A-920 associated particle neutron generator, an array of 12 NaI(Tl) detectors, a high-speed data acquisition system and a 160-core distributed data processing cluster has been built for the precise and accurate measurement of 846.8 keV and 1238.3 keV prompt γ-ray production cross section from 56Fe(n,n’γ)56Fe interaction. The merit of performance for this system and method includes (1) A fine timing resolution σ < 1.6 ns to distinguish the prompt γ-ray signal from thermal neutron capture or other noise; (2) Mono-energetic 14.1-MeV neutrons from the D-T fusion reaction are used to reduce the systematic error due to neutron energy variations when using the neutron Time-of-Flight (n-TOF) method; (3) The associated α-particle is used to trigger the data acquisition system thus reducing the systematic error due to the neutron flux measurement found using the fission chamber method; (4) The gamma ray detector array’s geometric acceptance was ~8% covering a significantly larger scattering solid angle assuring better accuracy in the measurement of the integral cross section; (5) A independent offline parallel data processing algorithm was developed providing full control of the data flow. The APNEI technique may well be the best approach for precision cross section measurements using 14.1-MeV neutron induced prompt γ-rays within the energy region from 500keV to 5MeV.
Koltick, Purdue University.
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