Application of the Reduced-Fitting Method to determine neutron scattering

Abstract

As the number of techniques using neutron radiation has grown, the number of neutrons detectors has increased along with need for their calibration. In Brazil this substantial demand for neutron detector calibration falls on a single laboratory located in Rio de Janeiro. One of the major problems in the calibration of neutron detectors is neutron scattering, which varies depending on the size and configuration of the laboratory. This is due to the neutrons that interact with the experimental setup and the surrounding, walls, floor and ceiling. This scatter influences the reading of the instrument to be calibrated and causes systematic errors in the calibration of neutron detectors. ISO 8529-2 recommends the following methods to correct these effects: The Semi-Empirical Method (SEM), the Reduced-Fitting Method (RFM), the Shadow-Cone Method (SCM) and the Generalized Fit Method (GFM). In this study, the neutron scattering characterization was performed in the Neutron Calibration Laboratory (LCN) of IPEN/CNEN, using the RFM method. The neutron source used was 241AmBe, which was positioned in the center of the calibration room. Neutron spectra were obtained using a scintillation detector based on 6Lil(Eu) in combination with a Bonner sphere spectrometer (BSS) at source-detector distances from 30 cm to 258 cm.