CHARACTERISTIC AND OPTIMIZATION OF AN IMAGING PLATE NEUTRON DETECTOR. Karasawa Y., Niimura N., Yamada T., Moriai A., Takahashi K(1)., Tazaki S(1)., Miyahara J(1) Japan Atomic Energy Research Institute, Tokai, Ibaraki, 319-11, Japan, (1)Fuji Photo Film Co., Ltd. Kanagawa, 258 Japan

The properties of imaging plate neutron detectors (IP-ND) were investigated by varying the molar ratio of neutron converter materials to a photostimulated luminescence materials (PSL) and IP-ND thickness in the wide range and systematically, and optimization of IP-ND was discussed by considering the basic processes occurring in the IP-ND. We have already developed and reported the IP-ND where the neutron converters, 6LI or Gd were mixed with PSL materials on a flexible plastic support. The dynamic range and spatial resolution of our IP-ND were obtained as 1:105 and less than 0.2 mm, respectively and the neutron detection efficiency of some IP-ND reached about 80 % at neutron wavelength 1$B!(B (Niimura, Karasawa, Tana ka, Miyahara, Thakahashi, Saito, Koizumi & Hidaka, Nucl. Instrum. & Methods A349(1994) 521). These distinctive features are more revolutionary and excellent than any other neutron detectors existing so far and must be applicable for many fields of neutron beam experiments. The properties of the IP-ND depend on the kind of the neutron converter, the molar ratio of neutron converter to PSL materials, thickness of the IP-ND and so on and the optimization was treated by considering three processes occurring in the IP-ND. Those are (1) neutrons are captured by neutron converters and they emit secondary charged particles.(2)which create color centers. (3)In read out procedure, both incident and PSL lights absorb themselves in the IP-ND.

The applications of the IP-ND to several experiments such as neutron crystallography in biology, radiography, powder diffractometer, small angle thermal neutron scattering and so on have been demonstrated and the excellent results have been given. The neutron diffractometer equipped with the optimized IP-ND dedicated for bio-macromolecules has been constructed in JRR-3M in Japan Atomic Energy Research Institute. Data acquisition speed of the diffractometer has increased more than 10 times than the one of the normal position sensitive gas filled detector.