Beam characterization for neutron imaging after installation of the external collimator at TRR-1/M1

Abstract

The neutron imaging facility at Thai Research Reactor-1/Modification 1 (TRR-1/M1), located at Thailand Institute of Nuclear Technology (Public Organization) has been improved for non-destructive characterization of internal structure of materials. The aims are to study the beam characteristic after an installation of the external collimator, and to optimize the exposure condition for a new setup. The neutron imaging setup was modified to increase the L/D ratio. As a consequence of the extended distance from the beam port to the sample position, an external collimator was installed to focus the neutron beam since 2018. Moreover, a new sample holder was installed to support sample rotation and translations with increased stability. The experiment was performed at the TRR-1/M1 reactor with 1 MW-reactor power. The neutron beam at the 8-inches south beam port of the TRR-1/M1 was evaluated in terms of beam homogeneity and the relationship between the grayscale value and image quality obtained from a CCD camera. The present performance of the neutron imaging system was tested with an ASTM standard sample, called sensitivity indicator. The results are shown in terms of image contrast and sharpness.