Abstract
The diagnostic methods for the profile of the radiation source were estab-lished at first based on the pinhole imaging principle. In this paper, the relationships among various parameters of the gamma-rays crammer such as the modulation transfer function (MTF), the noise power spectrum (NPS), the signal-noise ratio (SNR) and the detective quantum efficiency (DQE) are developed and studied experimentally on the cobalt radiation source. The image diagnostic system is consisting with rays-fluorescence convertor (YAG crystal), optical imaging system, MCP image intensifier, CCD camera and other devices. The spatial resolution of the modulation transfer function (MTF) at 10% intensity was measured as 1 lp/mm by knife-edge method. The quantum of the measurement system is about 150 under weak radiation condition due to the single particle detection efficiency of the system. The dynamic range was inferred preliminarily as about 437. The required radiation intensity was calculated using the experiment result for the (SNR) = 1, 5, 10, respectively. The theoretical investigation results show that the radiation image with (SNR) = 1 can be only obtained when the pinhole diameter is 0.7 mm, object distance and image distance are both 200 cm, and the radiation intensity is about 1.0 × 1012 Sr-1·cm-2.
Highlights
Introduction*1) Sponsered by: National Natural Science Foundation of China (Contract No 11005095, 11305155). 2) About the author: Hongwei Xie (1966), male, associate professor, master of science, mainly engaged in the study of image diagnostics of pulse radiation source
The theoretical investigation results show that the radiation image with signal-noise ratio (SNR) = 1 can be only obtained when the pinhole diameter is 0.7 mm, object distance and image distance are both 200 cm, and the radiation intensity is about 1.0 × 1012 Sr−1⋅cm−2
The spatial resolution of the thick pinhole imaging system could not be measured in certain conditions, which could be obtained mainly based on the theoretical design and related theoretical calculation
Summary
*1) Sponsered by: National Natural Science Foundation of China (Contract No 11005095, 11305155). 2) About the author: Hongwei Xie (1966), male, associate professor, master of science, mainly engaged in the study of image diagnostics of pulse radiation source. On the other hand, imaging based on radiation source combined with thick pinhole is an ideal method of nondestructive detection with high spatial resolution. Performance of the imaging diagnostic system is calibrated with three main technical specifications: the modulation transfer function (MTF) [4], the noise power spectrum (NPS) [5] [6], and the detective quantum efficiency (DQE) [7] [8]. In the case of the diagnostics of the high energy radiation sources, due to the relatively intense penetration effects of the γ-rays, the edge method becomes the major method to determine the MTF, which is represented by the Fourier Transform of the linear spread function (LSF). The effects of these parameters upon the image quality are evaluated and studied experimentally
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