Research in High-resolution Neutron Imaging at China Advanced Research Reactor

Abstract

Neutron imaging is a transmission imaging method, which has a wide range of applications in the fields of non-destructive testing of internal defects in materials, the distribution of light elements in samples, and the detection of radioactive samples due to the advantages of neutrons with deep penetration, ability to distinguish isotopes, and sensitivity to light elements. With the continuous development of various application fields, the requirements for the spatial resolution of neutron imaging are getting higher and higher, and improving the spatial resolution of neutron imaging and continuously approaching the micron level has become a key research direction in the field of neutron imaging. At present, the international advanced neutron imaging device has been able to complete the high-resolution neutron imaging test with spatial resolution at the micron level, and the domestic research in this field has also made some progress with the completion of the three major neutron sources, and is gradually approaching the international advanced level. The thermal neutron imaging device and the cold neutron imaging device of the China Advanced Research Reactor have been completed and put into use in recent years, and the maximum neutron flux density at the sample of the device can reach 4×109 cm−2·s−1, the optical path system has been greatly improved compared with the original neutron imaging device, and the spatial resolution of the detector has reached the sub-millimeter level, which has been widely used in aerospace, cultural relics and archaeology, hydrogen content characterization and other fields. The main factors affecting the spatial resolution of neutron imaging in neutron imaging devices are neutron sources, neutron optical path systems and neutron imaging detectors. In this study, based on the relevant test requirements in the fields of zirconium alloy hydrogen content and cultural relics production technology, the influencing factors of neutron imaging spatial resolution were studied, and a set of high-spatially resolved neutron imaging detectors based on the thermal neutron imaging device of China Advanced Research Reactor was built. At the same time, the spatial resolution of the detector was calculated theoretically, and the detector was debugged as a whole. Finally, the relevant band bundle commissioning of the detector system was completed on the thermal neutron imaging facility of China Advanced Research Reactor, and the syringe needle samples were tested. The test results show that the spatial resolution of the detector reaches 11.3 μm, and the actual available field of view size reaches 23.6 mm×28 mm, achieving a spatial resolution of 10 μm.

Keywords

• neutron imaging
• neutron detection technique
• spacial resolution