Bragg-edge neutron transmission spectrum analysis using a high-speed-camera-type time-of-flight neutron imaging detector

摘要

Thus far, quantitative imaging of crystallographic information using a time-of-flight (TOF) neutron Bragg-edge transmission method has been performed using counting-type neutron TOF-imaging detectors. However, at intense pulsed neutron beam facilities, the limit of the maximum counting rate of the detectors restricts acceptable neutron intensity. A camera-type neutron imaging detector can accept considerably higher neutron intensity than counting-type detectors. For this reason, a camera-type detector applicable for the TOF measurement has been developed. However, the camera-type detector has not been applied to quantitative analysis of crystallographic information thus far. As the neutron spectrum data obtained by a camera-type detector may have different characteristics compared with those obtained by a counting-type detector, it is important to experimentally demonstrate the applicability of the camera-type detector for quantitative crystallographic analysis. Thus, in this study, we performed a demonstration experiment using a steel knife specimen at a beam-line connected to a coupled-type neutron moderator of the Hokkaido University Neutron Source (HUNS). We applied the Rietveld-type data analysis method to measured Bragg-edge neutron transmission spectra in order to obtain quantitative crystallographic information, and we then conducted the crystalline phase imaging. Finally, using the new detector system along with the spectral analysis, the results were obtained non-destructively; the results showed that the crystalline phase distribution of the steel knife composed of two phases was changed gradually, and the crystallographic texture and crystallite size distributions were almost uniform. In addition, the new detector system provided the best spatial resolution of 520 mu m at a field-of-view of 13 cm x 13 cm.