J-PARC MLF ANNRIでのニオブの中性子全断面積の測定

Niobium(Nb)-$93$, which is mono isotope, is one of the material elements to strengthen stainless steel and is used for structural materials of nuclear reactors. Since Nb is also used as an element of superconductor alloys, it has been used in fields such as fusion reactor and accelerator development. Determination of neutron total cross section with high accuracy is therefore required in the field of nuclear technology. The cross sections of Nb were measured by T. Wang(2011), N. J. Drindak(2006) and so on. However, the resonance parameters determined by them have discrepancies up to about 10% each other. In order to determine the more precise values of resonance parameters, transmission measurements were performed to evaluate total cross section of $^{93}$Nb at the ANNRI of MLF in J-PARC in June of 2019. The ANNRI is one of beamlines in MLF, and Germanium gamma-ray detectors and the Liglass neutron detectors are installed to measure nuclear reactions. A target was natural Nb plate of $25$ mm $\times$ $25$ mm $\times$ $10$ mm$^\rm{t}$ whose size was determined from necessary statistic. Since the target size was big and the thermal-neutron capture cross-section is small (about 1.1 barns), the effect of neutron diffraction was observed in low neutron energy region. When discussing reactions to a single nucleus, the effect of diffraction resulting from crystal structure is unnecessary information. Thus, this effect must be estimated and removed to determine the total cross section as nuclear data for a single nucleus. In this poster, I will present preliminary results of the experiment and the estimated effects of neutron diffraction. This work has been supported in part by Grants-in-Aid for Scientific Research (JP17H01076).