Speaker
Description
Compton backscatter imaging is a radiographic non-destructive testing technique that utilizes the Compton scattering effect to acquire internal structural information of objects. It has wide applications in fields such as medicine, pipeline inspection, corrosion detection, security, and aerospace. Compared to other non-destructive testing methods, such as ultrasonic testing and eddy current testing, Compton backscatter imaging can rapidly provide precise three-dimensional images. Unlike transmission X-ray imaging techniques such as Computed Tomography and Digital Radiography, both the X-ray source and the detector are located on the same side of the object in Compton backscatter imaging. This setup not only simplifies the imaging process but also broadens its applicability, especially in scenarios where access to the opposite side of the object is limited or impractical, such as during archaeological excavations. In archaeology, the ability to rapidly obtain millimeter-scale subsurface images has profound implications. It not only enhances the speed and accuracy of archaeological digs but also aids in the careful handling and conservation of unearthed relics by minimizing direct contact and potential damage. Recognizing these benefits, we have successfully designed and constructed a prototype of a high-precision Compton backscatter imaging system for archaeological excavation. The system primarily consists of an X-ray tube, a slit collimator, and a scintillator detector. The system acquires the directional information of the scattered photons through the slit collimator and obtains the electron density information at corresponding positions based on the counts in different detector pixels. An industrial X-ray tube was used to irradiate the object being inspected. X-rays from the X-ray tube have a continuous energy spectrum. X-rays are collimated to a pencil beam that is directed vertically onto the surface of the object. The tungsten collimated slit allows only the photons passing through the slit collimator to reach the detector. To analyze the energy of the scattered photons and improve the signal-to-noise ratio of the reconstructed images, we used a gadolinium aluminum gallium garnet scintillator detector array to record both the number and energy of the scattered photons. Experiments were conducted on phantoms composed of soil containing metal using this prototype system. The experimental results showed that multiple scattered photons have a lower average energy compared to single scattered photons. These multiple scattered photons reduce the signal-to-noise ratio of the images. Therefore, appropriately increasing the energy threshold, although it reduces the total number of photons, improves the image quality. The achieved depth resolution of the system exceeded 1 mm, with a maximum penetration depth of several centimeters, demonstrating its suitability for uncovering buried structures. Compton backscattering imaging holds application value in providing underground information for archaeologists. In the future, we will further investigate how energy information can improve the image quality of backscatter imaging to further refine the quality of backscatter images.
