Performance Evaluation of a Combined Neutron and X-ray Digital Imaging System

摘要

A neutron and X-ray combined computed tomography system (NXCT) has been developed1 at the Missouri University of Science & Technology. It is believed that it will provide a superior method for non-destructive testing and evaluation. The system is housed within the Missouri University of Science & Technology Reactor (MSTR) and is the first such imaging platform and synthesis method to be developed. The system utilizes neutrons obtained directly from the reactor core and X-rays an X-ray generator. Characterization of the newly developed digital imaging system is imperative to the performance evaluation, as well as for describing the associated parameters. The preliminary evaluation of the NXCT system was performed in terms of image uniformity, linearity and spatial resolution. Additionally, the correlation between the applied beam intensity, the resulting image quality, and the system sensitivity was investigated. The combined neutron/X-ray digital imaging system was evaluated in terms of performance parameters and results are detailed. The MTF of the X-ray imaging module was calculated using the Edge method. The spatial frequency at 10% of the MTF was found to be 8 lp/mm, which is in agreement with the value of 8.5 lp/mm determined from the square wave response method. The highest detective quantum efficiency of the X-ray imaging module was found to be 0.13. Furthermore, the NPS spectrum for the neutron imaging module was also evaluated in a similar way as the X-ray imaging module. In order to improve the image quality of the neutron imaging module, a pin-hole mask phantom was used to correct the geometrical non-linearity of the delay line anode readout. The non-linearity correction of the delay line anode readout has been shown through the corrected images of perforated cadmium strip and electroformed phantom.