Development of Dual Energy Container Inspection System for Harbor Security in KAERI

The use of multiple energy X-rays can provide additional information as compared to a single energy X-ray for the security inspection of cargo such as containers. Using the 9/6 MeV dual energy X-ray and material discrimination algorithms, it is possible to distinguish between low-density (organic) and high-density (inorganic) materials through the intended color mapping. The material discrimination algorithm can obtain the material information of the image used for screening by exploiting the characteristic that the energy-dependent attenuation coefficient is different even though the same material is used. Based on these technologies, we have developed a security inspection system for container cargo that consists of a radiation source, a detector array, four-collimators, a moving stage, and an imaging system. The radiation source was developed based on a dual-energy radiofrequency (RF) electron linear-accelerator (LINAC) with a spot size of 0.9 mm, and a 5.5 MW S-band magnetron was used as a RF generator. The detector is composed of 43 modules in one array and 32 channels per module, and the moving stage is designed and manufactured to transport cargo of up to 70 tons in the horizontal direction of the radiation beam at an optimized speed of 300 mm per second. The imaging system controls the whole process of the security inspection system from the operation of equipment to the acquisition and discrimination of images. In this paper, we introduce the characteristics of the developed inspection system and explain the results obtained by ANSI N42.46, the international recommendation standard for a container scanner performance test.