Studies on neutron beam probes. Development of neutron beam control systems

The neutron is a very unique probe since it can penetrate into materials and also observe elements that are difficult to be seen by other radiations. Due to these characteristics neutrons are essential in various measurements such as residual force in nuclear plant parts, and structures and dynamics of biomaterials and polymer. However, it is important to increase the intensity. Development of neutron beam control systems is very important to get high-intensity well-collimated beam. Here, we report studies on neutron beam control devices of a magnetic lens, a multi capillary fiber and a mirror. The first observation of focusing effect by using a magnetic lens was achieved in this study. Intensity gain of about 40 times was attained at a focusing wavelength. It was revealed that the factor would be increased to 80 times by improvement of homogeneity of the magnetic field. Neutron transmission rate through a multi-capillary fiber was observed as a function of wavelength, also at different capillary radii and curvatures. The rate became constant above about 5A and higher in larger radius capillary than small one. The results indicate that there is optimal capillary radius depending on the neutron wavelength. So, it is necessary to take account this when making a realistic model. To use a single beam line more effectively, we make a neutron beam splitter using super mirrors to get two beam lines with different neutronic characteristics. It was demonstrated one beam line supplied about twice higher intensity at longer wavelength compared with usual one. It is well recognized that development of the neutron beam control system is so important because of necessity of neutrons as a probe. Progress of this study contributes to apply the neutrons to be field of nuclear engineering. (author)