Validation of the Monte Carlo model of the LOENIEv2 long counter for absolute efficiency calculation

• Published in: EPJ Web of conferences 2024, Vol.294, p.1009
• Main Authors: Leconte, Pierre, Geslot, Benoit, Kooyman, Timothée, Belverge, Dorian, Boffy, Romain
• Format: Article
• Language: English
• Subjects: Anisotropy; Californium isotopes; Computational efficiency; Efficiency; High density polyethylenes; Neutrons; Radioactive materials; Sensors; Tubes; Uncertainty
• ISSN: 2100-014X; 2101-6275; 2100-014X
• DOI: 10.1051/epjconf/202429401009

LOENIEv2 is a long counter detector used for delayed neutron (DN) measurements. It is composed of sixteen 3He tubes embedded in a cylindrical high-density polyethylene (HDPE) matrix. Thanks to a special arrangement of the 3 He tubes in three concentric rings, relative variations of the total efficiency as low as 2% can be reached over the [0.1 – 1 MeV] energy range. This paper addresses the development of a Monte-Carlo model of the detector and its validation thanks to calibrated neutron source measurements, performed at the NPL institute. These sources are in the form of small cylinders containing either a spontaneous fission material ( 252 Cf) or a radioactive material producing neutron through (Α,n) reactions (AmLi, AmB, AmF, AmBe). These sources are well characterized in emission rate, spectrum and anisotropy so that they can used as standards for efficiency calibration. Using the JEFF-3.3 nuclear data library, the calculation of the detector absolute efficiency is validated within experimental uncertainties. The averaging of [C/E-1] values between the different sources end up to an estimated bias of -0.3% with an uncertainty of ±0.6% (1σ) over the range [0.5 – 4.1 MeV].