Development of a digital γ spectral logging probe
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摘要: 针对铀钍混合型矿床上无法精确测量地层中铀、钍含量的问题, 本文研制了一台基于溴化铈晶体的数字化γ能谱测井探管。该仪器采用直径38 mm×38 mm的溴化铈晶体, 提高了铀灵敏度和在低铀、低钍含量矿层的探测效率。采用C8051单片机作为核心处理器, 对溴化铈探测器原始信号进行了滤波成形处理, 通过能谱采集器得到γ能谱数据。通过对γ能谱数据进行逆矩阵解谱, 即可得到矿层中铀、钍的精确含量。通过RS-485总线将γ能谱数据传送至测井主机。测试结果表明:本仪器在标准铀钍混合模型上的测量准确度高, 其示值误差小于6%, 稳定性小于1.5%, 重复性小于1%, 钍系208Tl的2.62 MeV能量峰漂移不超过±0.3道, 检查测井异常相对误差小于4%, 可应用于铀矿勘查测井工作。Abstract: Given that it is difficult to accurately determine the uranium and thorium contents in the strata of uranium-thorium mixed deposits, this study developed a digital γ spectrum logging probe based on cerium tribromide (CeBr3) crystals.Using CeBr3 crystals with a diameter of 38 mm×38 mm, the logging probe improved the sensitivity to uranium and the detection efficiency of ore beds with low uranium and thorium contents.The logging probe operated as follows.First, the original signals from the CeBr3 detector were filtered and shaped using the C8051 single-chip microcomputer as the core processor.Then, the γ spectrum data were obtained using the energy spectrum collector.After the spectrum unfolding based on the inverse matrix is performed for the γ spectrum data, precise uranium and thorium contents in the ore beds were obtained.Finally, the γ spectrum data were transmitted to the host computer for logging through the RS-485 bus.The results show that the logging probe had high measurement accuracy in the standard uranium-thorium mixed model, with indication errors of less than 6%, stability of less than 1.5%, and repeatability of less than 1%.Moreover, the 2.62 MeV energy peak drift of thorium 208Tl did not exceed ±0.3 channels, and the relative errors of log anomalies were less than 4%.Therefore, the digital γ spectrum logging probe proposed in this study is applicable to the exploration and logging of uranium deposits.
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