High energy X-ray computed tomography for industrial applications

A high-energy X-ray computed tomography system with an electron linear accelerator was developed to image cross-sections of large-scale and high-density materials. An electron linear accelerator is used for the X-ray source. The maximum X-ray energy is 12 MeV and the average energy is around 4 MeV. The intensity of an X-ray fan beam passing through the test object is measured by a 15-channel detector array. CWO (CdWO/sub 4/) scintillators and photodiodes are employed for the X-ray detectors. The crosstalk noise due to scattering at X-ray photons by adjacent detectors is reduced to less than 1.6% by installing a tungsten shield between the scintillators. Extra channels are used to compensate for the baseline shift of the circuits. These techniques allowed attainment of a dynamic range of more than 85 dB and a noise level comparable to the signal amplitude of X-ray transmitted in a 420 mm-thick iron block. A spatial resolution of 0.8 mm was confirmed with an iron test piece 200 mm in diameter.<>