High Resolution Computed Tomography for Industrial Applications based on Coherent Fiber Optics Ribbons

An innovative system for high resolution computed tomography for typical energies used in industrial inspection applications has been recently developed at the Department of Physics of the University of Bologna. Nowadays, it is difficult to obtain high resolution (<100 microns) of industrial parts made of metal such as castings, turbine blades and similar components that have dimensions of several tens of centimeters. This is due to both the high number of sampling points and views needed to achieve a good reconstruction and the high energy of X-ray radiation required to penetrate the material, combined with a number of physics-related problems and limitations. A detector designed and optimized for this task should be fast and should have a good efficiency and a high dynamic range. The linear detector developed at the Department of Physics allows to obtain an image definition with a pixel size of 25 microns over a 500 mm × 5 mm wide field of view using a 3 mega pixel CCD camera and potentially around 16 microns with a 9 mega pixel CCD camera. It consists of a coherent fiber optics light guide whose output is acquired by a high sensitive and low noise cooled CCD camera. This set-up allows collecting a good signal, being fast, having an optimized dynamic range and keeping the resolution high. Other advantages are the exchangeable scintillator and the flexibility of the fibers that allow putting the camera off-beam. The system has been tested for the first time with a 450 kV typical industrial X-ray tube at Empa (Swiss Federal Laboratories for Materials Testing and Research) in Duebendorf, close to Zurich, (Switzerland) in March 2006. Measurements will be described in detail and results reported in this paper.