Performance of the Bragg-edge Transmission Imaging at a Compact Accelerator-driven Pulsed Neutron Source

Abstract

Performances of the Bragg-edge transmission imaging at a compact accelerator-driven pulsed neutron source (pulsed CANS) are presented and evaluated. This technique is expected to be a new material analysis tool that can quantitatively visualize crystalline microstructural information inside a bulk material over large area with reasonable spatial resolution non-destructively. Therefore, it is expected that such new useful instrument should be installed at not only world-leading pulsed spallation neutron sources but also popular-priced CANS. For this reason, we evaluated and discussed the performances of the Bragg-edge transmission imaging at CANS for potential users. A coupled moderator is usually used to gain higher neutron flux at CANS. In such situation, quantitative imaging of crystal lattice strain and crystalline phase is not easy due to the low wavelength resolution. However, according to Monte-Carlo simulation calculation studies, it was found that an experimental setup using a decoupled moderator connected to a supermirror guide tube can solve this problem. On the other hand, in the situation using the coupled moderator, quantitative imaging of crystallographic texture and crystallite size can be carried out, but the Rietveld-type data analysis software, RITS, is necessary to evaluate reasonably low statistics data measured at CANS. Furthermore, it was found that reasonable results can be obtained by the Bragg-edge transmission imaging with the RITS code at CANS, which are consistent with results of a high-performance neutron diffraction experiment with the Rietveld analysis at a world-leading pulsed spallation neutron source. This means the Bragg-edge transmission imaging is expected to be one of the most efficient crystallographic/metallographic analysis tools for CANS.