Gadolinium oblique evaporation approach to make large scale neutron absorption gratings for phase imaging

Neutron phase imaging is a developing technology following the earlier development of X-ray phase imaging using gratings. Making high aspect ratio structures for neutron gratings is crucial to ensure the sufficient function of neutron absorption gratings, for which the usage of Gd is effective. Oblique evaporation of Gd on a Si grating is an excellent approach for Gd grating fabrication, but non-uniformity is a remaining problem in fabricating gratings large enough for the required field of view of neutron phase imaging. In this study, we propose a fabrication process, in which a Si grating is moved during the oblique evaporation process to attain uniform deposition of Gd in a 64 mm × 64 mm area. X-ray microtomography was used to evaluate fabricated gratings by depicting deposited Gd density distribution in grating units cut out by a focused ion beam (FIB). (author)