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中文摘要：
多相流体特征参数的准确测量是国际上亟待发展的探索性研究课题，断层成像技术是多相流检测技术的一个重要研究方向。本系统利用射线透射原理，结合多相流复杂多变的流动特性，设计了基于γ射线的多相流在线检测系统。该系统由探测单元、数据采集及信号处理单元、计算机图像重建单元三部分组成，其中探测单元采用5个能量为59.5 keV的241Am源，5组CdZnTe半导体探测器阵列均匀分布于管道截面实现实时同步检测。为提高探测精度，设计了由低噪声电荷灵敏前置放大单元、具有零极点相消的低噪声主放大单元以及滤波单元组成的低噪声探测电路。测试结果表明，常温下系统对于59.5 keV的241Am源，其能量分辨率为4.38%。应用实验测试数据，利用滤波反投影算法对多相流的典型流型进行了图像重建，实验表明该系统的有效性。
英文摘要：
In the present paper, a gamma-ray based on-line detection system was designed for multi-phase flow measurement, where the complicated fluid property of multi-phase flow can be studied by using the principle of ray transmission. The system is made up of three parts, i. e. , the sensing unit, the signal conditioning ＆ processing unit and the computer imaging unit. The sensing unit consists of five ^241Am sources with principal energy of 59.5 keV and five sets of CAZnTe semiconductor detectors by using the Geant 4 simulating software toolkits. The sources and detectors are mounted equally at the cross section of pipeline to detect different phase medium simultaneously. This function of the system guarantees the real-time performance of the on--line detecting. In order to improve the accuracy of the probe, a low noise probe circuit was designed, including a low noise chargesensitive preamplifier, a low noise amplifier, filter circuit and an eliminated zero-poles circuit. Some of the emitted gamma-ray photons from the radiation sources are detected by the sensing element, where the photo energy is transferred into electrical energy by using CdZnTe semiconductor detectors. The output of the sensing element is sent to the signal conditioning ＆ proeessing unit, which is amplified and filtered to be a level-discriminated signal. Finally, the output of the signal conditioning ＆ processing unit is sent to the computer imaging unit, in which the 2D images are reconstructed by using a certain reeonstruetion algorithm. Under the normal temperature, the system performs the test of energy spectrum and then it has better energy resolution about 4. 38% for ^241 Am 59.5 keV. The result reveals that our system has higher probe accuracy. Using experimental data, the images are reeonstructed with Filter back projection （FBP） reconstruction algorithm. Images of high quality are achieved.
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