Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2016-10, Vol.833, p.61-67
• Main Authors: Ikeda, Yoshimasa, Taketani, Atsushi, Takamura, Masato, Sunaga, Hideyuki, Kumagai, Masayoshi, Oba, Yojiro, Otake, Yoshie, Suzuki, Hiroshi
• Format: Article
• Language: English
• Subjects: Compact accelerator-based neutron source; Moderation time; Neutron engineering diffraction; Resolution; Time-of-flight
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2016.06.127

A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by a large sampling volume with 10mm in cubic for an acceptable measurement time, i.e. 10min. The minimum resolution of the 110 reflection for RANS is approximately 2.5% at 8μs of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30μs, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time by decreasing a thickness of the moderator or by applying the decoupler system or application of the angular dispersive neutron diffraction technique are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenitic phase in the dual phase mock specimen was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS has been proved to be capable for neutron engineering diffraction aiming for the easy access measurement of the texture and the amount of retained austenite.