Improvement of Large Container Inspection System in Photon- Counting Mode Proved With Steel Penetration Ability

Abstract

Abstract We present the structure and characteristics of a photon-counting system for increased Steel Penetration (SP) ability in large container inspection area. Ideally, radiation images should count only unreacted photons. Conventional detectors utilize analog current integration and thus suffer from scattered signals and electronic noise which can deteriorate image quality. However, with the increasing demand for container inspection, higher requirements have been placed on image quality, scan speed as well as radiation dose. Therefore, we propose a new photon-counting mode large container inspection system that counts individual signals, in which scattered signals and electronic noise can be eliminated by setting an energy threshold. In this paper, we give a system overview and describe the key technologies in system design. Then the improvement of the presented system is analyzed theoretically from the aspect of physical interactions that take place in the system. Simulation of the Steel Penetration model is conducted in Geant4 software. Results show that the improvement of SP ability compared with the conventional current-integration system is about 3 to 4cm Fe even if we increase the scan speed or reduce the radiation intensity, and can be 1 to 2cm more by setting an appropriate energy threshold. Along with this property, the possibility of reducing radiation dose and increasing scan speed makes this system unique for future growth of container inspection missions.