【作者】 陈方强；

【导师】 葛良全；

【作者基本信息】 成都理工大学 ， 核资源与核勘查工程， 2011， 硕士

【摘要】 国内外有关专家学者对γ谱数据处理的算法和应用开展了大量卓有成效的研究,但是,将全谱解析方法应用到能谱系统标定中的研究却鲜有见闻。能不能用更少的标准模型或者标准样品,以更简洁的方式,对航空γ谱仪测量系统进行可靠而精确的散射标定,并达到一定的精度,值得研究;新型国产航空γ谱仪研制后,其具体性能指标是人们所关心的,各项指标通过哪些切实可行、有效精确的方法进行测定,值得探讨;系统在有关试验中的响应情况如何,自然界中,陆域、水域和海域不同高度不同能量γ射线随高度的变化规律如何,值得分析。本课题来源于于国家863计划资源与环境技术领域重大项目航空地球物理勘查技术系统的第七课题──航空伽玛能谱勘查系统研发。本文主要针对航空γ能谱仪主要性能测试、不同环境上空不同能量γ射线随高度的变化规律、系统的标定方法展开研究。论文首先介绍了航空γ能谱测量中主要的辐射源及其特征,并利用圆锥体模型对地表上空的γ照射量率的计算方法进行了分析和讨论;接着,对航空能谱测量常见天然原始谱、谱信号的形成过程及实测仪器谱的复杂化进行了深入分析;然后对论文的主要研究内容和成果进行了详细论述。主要研究内容和成果有:(1)分析谱仪的主要性能指标及其含义,研究重要指标的测试方法。在裸晶体和低本底两种条件下分别测定能量分辨率,对Cs源661KeV能量峰而言,两种条件下的单条探测器分辨率均小于8%,室内系统分辨率小于8.4%;利用U源、Th源的多特征峰及能量线性的公式求取能量起始阈小于23KeV、各条探测器和系统能量线性拟合度均大于0.9999,积分非线性小于0.2%,微分非线性小于1.0%,系统上限计数率达200K/sec;利用双源净计数法测定系统的死时间小于5μs;任意抽取稳定的室内环境24小时稳定性测试中的4小时数据进行分析,各窗计数率与均值相对误差均小于±10%,其中总道的相对误差为±6.29%;在温湿度随时间变化的室外环境进行48小时稳定性测试,结果表明计数率随地面湿度增大而减小;1024道模式下调偏16道,系统在90s后达到较好的稳谱效果。(2)利用水、陆动态标定带数据,对谱仪系统在陆地、湖面上空300m范围内各能窗计数率随高度的变化规律进行分析,得到陆地和水域上低空范围不同能量γ射线随高度的变化规律;利用海上高高度标定数据,对各能窗计数率在海域上空1800m至3000m范围内随高度的变化规律进行分析,得到海域上空较高高度不同能量γ射线随高度的变化规律。(3)在充分调研和分析的基础上,选择SINP和傅里叶变换相结合的方法对仪器谱进行精确本底扣除,然后利用直接解调方法进行全谱解析,并将该方法应用到系统标定上来。采用剥离系数法和航空标定模型对车载、Y-5飞机机载、Y-12飞机机载系统进行系统标定,其中谱漂严重的车载试验的标定结果明显错误,表明谱漂较严重时散射剥离将失去意义。将利用剥离系数和全谱解析法得到的换算系数,对混合模型含量进行反算、对比,两者与含量推荐值的相对误差相当,证明了全谱解析标定方法在航空伽γ能谱系统标定中的可行性和精确性。(4)分别采用少量单点谱数据、所有数据参与全谱解析标定计算,结果表明采用更多谱数据参与计算,可有效抑制统计涨落影响;利用K、U、Th模型计算得到一组换算系数,利用混合模型计算得到另一组换算系数,比较两者的相对误差,结果表明两者相对误差不超过2.2%,所以可以利用一个标准饱和模型(或大面积饱和样品)得到换算系数,从而有效减少标定的工作量。更多还原

【Abstract】 Fruitful research on gamma-ray data processing algorithm and application has done by experts and scholars in the domestic and foreign, however, will be the full spectrum of analytical method applied to the energy spectrum of research system calibration are rarely informed. Can or not use less of the standard model or standard sample for reliable and accurate scattering calibration of gamma-ray measuring system, with more concise way and a certain precision, is worth studying. When new aero-gamma spectrometer in domestic is developed, with the specific performance index is concerned, each index all need through the feasible and effective methods for precision measuring, this is worth discussing. In different testing, system how to respond, in different height range, the rule of different energy gamma rays with height change on waters, ground-launched and sea, all of this is worth researching.This article comes from the national 863 Program, the seventh issue of major projects of resources and environment technoloygy "airborne geophysical exploration technique system"—"Department of airborne gamma spectrometry survey ECR&D" (No. 2006A06A207). This article launched research mainly on main performance testing of airborne gamma spectrometer, the rule of different energy gamma rays with height change in different environment, the calibration approach of system. It firstly introduces main radiation source and its characteristics of airborne gamma ray spectroscopy surve, and the calculation method of eminence above the earth’s surface are analyzed and discussed by conical model. Then,deeply analyzes the common natural original spectrum of airline spectrum measurement, the forming process of the spectrum signal, and the complication of the measured instrument spectrum. Finally the paper’s main research content and the results are discussed in detailThe main research contents and achievements are as follows: (1) Analyze the main performance indexes and its meaning of spectral instrument. Research the test methods of key indicators In bare crystal and low background, measure the energy resolution under two conditions. In terms of 661KeV energy peaks of Cs source, all the resolutions of single detector in two conditions are less than 8%. Resolution of system is less than 8.4% in the indoor environment. Using many peaks of U and Th, and linear equation of energy, obtained the starting energy threshold which is less than 23KeV. Both the each detector and system’s degree of linear fitting of energy are more than 0.9999. The integral nonlinearity is less than 0.2%, and the differential nonlinearity is less than 1.0%. The maximum count rate of system reached 200K/sec. The dead time determination of system is less than 5μs by dual-source net count. Through arbitrary 4 hours data of 24 hours indoor stability testing, relative errors between count-rate of each window and the average count-rate are less than±10%. Among them, the count-rate of TC is less than±6.29%. For 48 hours stability testing, placed the system into outdoor environment where temperature and humidity changes with time, observations show that the count-rate decreases with the ground moisture. In 1024 mode, attune slants 16 channels, and the system will return to good spectrum-stabilizing effect in 90 seconds.(2) Using the data over the water and the land dynamic calibration belt below 300 metres, analyze the count-rate of different energy windows, thereby getting the rule of gamma-ray distribution by enery in low altitude above land and water. Using the data over the sea between 1800 and 3000 meters, analyze the count-rate of different energy windows, thereby getting the rule of gamma-ray distribution by enery in higher altitude above sea.(3) In full on the basis of investigation and analysis, select the method of combining SINP and Fourier transform into deducting the bottom of the spectrum instrument accurately. Then, use direct demodulation method for analyzing the full spectrum. This method is applied to system calibration. By stripping coefficient method and aviation calibration model, demarcate the system of on-board, on plane of Y-5, and on plane of Y-12. Among them spectrum drift seriously in the on-board test, there is a obvious mistake, when spectra drift show more serious, scattering detachment is meaningless. Comparing inverse calculation content of the hybrid model by the two methods, both the relative errors are similar with the recommended value. Demonstrate the full spectrum of analytical calibration gammaγenergy spectrum in the aviation system in the feasibility and accuracy of calibration. Proof the full spectrum analytical calibration method’s accuracy and feasibility in the calibration of aiborne gamma-ray spectrometer system(4) Using the method of full spectrum analytical calibration with a single point spectrum and all the data respectively, the calculation results show that using more datas will benefit the inhibiting of statistical fluctuation. By the model of K, U, Th, get a group of conversion coefficient, and another group by the model of M, both a relative error less than 2.2%. So can use a saturated standard model or sample to get conversion coefficients, thus the full spectrum analytical calibration method can reduce the workload of calibration effectively.更多还原