Proton radiography has provided a potential development direction for advanced hydrotesting, and its image blur is a crucial point that needs to be deeply studied. In this article, numerical simulation by using the Monte Carlo code Geant4 has been implemented to investigate the entire physics mechanism of high energy proton beam travelling through the object and beamline and arriving at the image plane. This article will mainly discuss the various factors which cause the image blur, including the chromatic aberration of the imaging beamline, the insumcient modulation of an incident particle＇s transverse displacement and angle deviation, the longitudinal length of an object, the influence of containment vessel and otherwise.
Proton radiography is a new scatheless diagnostic tool providing a potential development direction for advanced hydrotesting. Recently a low energy proton radiography system has been developed at the Chinese Academy of Engineering Phyiscs （CAEP）. This system has been designed to use an 11 MeV proton beam to radiograph thin static objects. This system consists of a proton cyclotron coupled to an imaging beamline, which is the first domestic beamline dedicated to proton radiography experiments. Via some demonstration experiments, the radiography system is confirmed to provide clear pictures with spatial resolution -100 μm within 40 mm field-of-view.
The magnetic lens(Zumbro lens) is a critical part in proton radiography. Traditionally the matched beam for Zumbro lens in proton radiography is a virtual point source beam, which is not suitable for some cases, such as cylindrical samples. In these cases, a parallel beam is more appropriate. In this paper, a method, which uses quadrupole beamline, is proposed for designing a magnetic lens with parallel beam matched. Theoretical analysis is given. The results show that the matched beam for this lens is indeed parallel beam, while the major merits of Zumbro lens are inherited. Following this method, a theoretical design based on the 11-Me V cyclotron is presented.
Guo-Jun YangZhuo ZhangTao WeiYi-Ding LiXiao-Ding ZhangJin-Shui Shi
Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron.The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve ~100 μm.
