Fast neutron radiography (FNR) with track etch technique

Neutron radiography of extended hydrogen containing objects is feasible only with fast neutrons, which guarantee sufficient radiation transmission. The imaging neutrons can be detected most reliably using plastic foils, by developing the tracts of locally corresponding recoil nuclei with an appropriate etching technique. This detection method is insensitive to photons, electrons, and thermal neutrons. There are defined correlations between etch pit and optical density, which allow optical recordings of foil images by the help of parallel light. The dependence of optical density on fast neutrons dose as well as on various etching conditions is reported. The relatively low image contrasts of single foils can be enhanced considerably by a multifoil stack detector. By this, the image quality is improved, and the neutron exposure can be lowered by at least one order of magnitude. Radiographic examples show advantages and possible applications of FNR with respect to technical materials as well as biological specimens and in vivo radiography. (orig.)