Application of very low energy neutron radiography with energy selection system using 4Qc(4m) supermirror

A high contrast neutron CT system is installed in the VCN/PF2 port of Institut Laue-Langevin and VCN port of Kyoto University Reactor (KUR). A converter+C-CCD system is used for the image detection. This system has an option of the energy selection system by neutron reflection on a 4Qc (4m) supermirror. The critical angle of the neutron reflection on this mirror is four times larger than that of natural nickel and the diameter is 20 cm. As the neutron reflection on a mirror removes faster neutrons, it can be used as a low pass filter of the neutron energy. The upper limit of the reflected neutron energy can be easily changed by the rotation of the mirror. As the application of this high contrast imaging system, the density nonuniformity of an aluminum welding sample can be shown by the refraction effect of very cold neutrons in VCN/PF2/ILL.