HIGH-ENERGY X-RAY COMPUTED-TOMOGRAPHY FOR INDUSTRIAL APPLICATIONS

A high energy X-ray computed tomography (CT) system with an electron l inear accelerator was developed to image cross-sections of large scale and high density materials. An electron linear accelerator is used fo r the X-ray source. The maximum X-ray energy is 12 MeV and average ene rgy is around 4 MeV. The intensity of an X-ray fan beam passing throug h the test object is measured by a 15 channel detector array. CWO scin tillators (CdWO4) and photodiodes are used for the X-ray detectors. Th e crosstalk noise due to scattering of X-ray photons by adjacent detec tors is reduced to less than 1.6% by installing a tungsten shields bet ween the scintillators. Extra channels are used to compensate for base line shift of the circuits. These techniques allowed attainment of a dynamic range of more than 85 dB and a noise level comparable to the s ignal amplitude of X-rays transmitted in a 420-mm thick iron block. Sp atial resolution of 0.8 mm was confirmed with an iron test piece 200 m m in diameter.