Abstract
The spatial resolution of the gamma-rays camera was measured on a60Co gamma-rays source with edge method. The gamma-rays camera is consisting with rays-fluorescence convertor, optical imaging system, MCP image intensifier, CCD camera, electronic control system and other devices, and is mainly used in the image diagnostics of the intense pulse radiation sources [1]. Due to the relatively big quantum detective efficiency (DQE) and quantum gain of the gamma-rays, etc., the experimental data were processed by averaging multiple images and fitting curves. According to the experimental results, the spatial resolution MTF (modulation transfer function) at the 10% intensity was about 2lp/mm. Meanwhile, because of the relatively big dispersion effects of the fluorescence transmissions in the scintillator and the optical imaging system, the maximal single-noise ratio (SNR) of the camera was found to be about 5:1. In addition, the spatial resolution of the camera was measured with pulse X-rays with 0.3MeV in average energy and exclusion of the effects of secondary electrons from consideration. Accordingly, the spatial resolution MTF at the 10% intensity was about 5lp/mm. This could be an additional evidence to verify the effects of secondary electrons induced by the 1.25MeV gamma-rays in the scintillator upon the spatial resolution. Based on our analysis, the dispersion sizes of the secondary electrons in the scintillator are about 0.4mm-0.6mm. Comparatively, as indicated by the detailed analysis of the spatial resolutions of the MCP image intensifier and CCD devices, both of them have little effect on the spatial resolution of the gamma-rays camera that could be well neglected.
Highlights
A γ-rays camera was developed for the image diagnostics of the intense pulsed γ-rays radiation sources, which was consisting with rays-fluorescence convertor, optical imaging system, micro-channel plate (MCP) + CCD, electronic control system and other devices
Evaluation of Major Factors Affecting Spatial Resolution of Gamma-Rays Camera scintillator and/or high energy, such a data processing might be technically difficult in various aspects as follows [4]: 1) the big DQE fluctuations induced by the interactions between the high energy γ-rays and scintillator; 2) the relatively big quantum gain of the γ-raysfluorescence convertor; 3) the relatively more measurement steps of the system
The modulation transfer function (MTF) and point spread function (PSF) could be well available after a certain process
Summary
A γ-rays camera was developed for the image diagnostics of the intense pulsed γ-rays radiation sources, which was consisting with rays-fluorescence convertor, optical imaging system, MCP + CCD, electronic control system and other devices. Evaluation of Major Factors Affecting Spatial Resolution of Gamma-Rays Camera scintillator and/or high energy, such a data processing might be technically difficult in various aspects as follows [4]: 1) the big DQE fluctuations induced by the interactions between the high energy γ-rays and scintillator; 2) the relatively big quantum gain of the γ-raysfluorescence convertor; 3) the relatively more measurement steps of the system. Another important factor to affect the spatial resolution is the measurement condition. The spatial resolutions of the camera components were studied respectively for the scintillator, MCP image intensifier and CCD camera, etc., to provide some valuable reference for the further improvement of the spatial resolution of the γ-rays camera
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