An experimental micro-CT system for X-ray NDT

摘要

This work describes the set-up of an experimental system for micro-tomography developed in the framework of a collaboration between the Physics Department of the University of Bologna (Italy) and the Geosphaera Research Center of Moscow (Russia). The main goal of this inspection system is to carry out high-resolution analysis in vitro of biomedical samples as well as nondestructive testing (NDT) of industrial components. The detection system consists of a 30x15 mm~2 rectangular fiber-optic taper (ratio 2:1) optically coupled to a cooled 12-bits CCD camera (1024x512 pixels). On the entrance window of the taper is deposited a thin layer of Gd_2O_2S:Tb phosphor which provides the X-light conversion. The image readout is carried out by means of a commercial frame grabber installed on a personal computer and specific software is used for data acquisition and control of the tomographic process. The object under investigation is arranged on a 3-degrees micro-positioning system (x-y translation and rotation) and irradiated by an X-ray microfocus beam (up to 200 kVp). The sample can be positioned easily along the source-detector axis in order to obtain a large magnification of details of interest. The X-ray detector has been intensively tested in order to determine its performance in terms of MTF, NPS, and DQE. Moreover, preliminary tests have been carried out on several samples in order to evaluate the performance of the micro-CT system.