Development of high resolution focusing collimators intended for nondestructive testing by the Compton scattering tomography technique

An original method for building high resolution focusing collimators with a great number of channels is described. The method consists of filling a mould with tungsten powder and impregnating it with a fluid epoxy resin, by pumping through the powder. The fine strips, used as cores for the channels, are then pulled out. The collimator that was built had 49 fine slots, all converging in one little bar-shaped volume, to convey x-ray photons from this volume to the entrance window of a large scintillation crystal detector. The collimator exhibits a very good precision of the relative positions of slots, allowing the volume V to be very sharply shaped. Use of this collimator for nondestructive testing by the Compton scattering tomography (CST) technique allowed us to detect plane defects down to 0.1 mm, inside composite plates.