Quantitative Measurement of Element Distributions using the Neutron-transmission Resonance-absorption Method

AbstractThe imaging method known as Neutron Resonance Absorption (NRA) is very suitable for nondestructive analysis of element distributions in a sample. The purposes of this study are to perform NRA test experiments using the Micro Pixel Chamber (μPIC), developed by Kyoto University and to confirm the quantitative quality of the measurements of the system. The experiment was performed at NOBORU in J-PARC. The detector was located at 14.5 m from the moderator in the experimental room. The samples, consisting of thin Cobalt, Tantalum and Molybdenum foils, were placed individually at the upstream from the detector. In the experiment, the transmission spectra with the samples and no sample were obtained. Background components were not so small in these measurements. From the neutron transport simulation, it was surmised that the origin of this background was due to scattering of neutrons in the experimental room. Therefore, the assumed background components were subtracted from the measurement data. Finally, it was found that the difference between the measurement data and the nuclear data was within about 20%. Issues remaining to be solved include how to obtain precise background data quantitatively in the case of a large absorption cross section