【作者】 黄秋；

【导师】 方方；

【作者基本信息】 成都理工大学 ， 核技术及应用， 2010， 硕士

【摘要】 近年来,氡对人体健康的危害已经引起广泛关注,因此空气氡的测量成为环境监测的热门技术。本文瞄准国内外空气氡现有的测量方法和测量仪器,分析其中不足:目前常用的空气测氡方法多为总量测量,这种方法难以将氡及其子体区分开来;而现有的能谱测氡仪如美国产的RAD7型α能谱测氡仪由于其采用动态泵吸方式收集氡气,对测量环境氡气场扰动较大,因此测量结果有一定误差。为了克服现阶段大多数空气测氡仪的技术不足,针对空气氡浓度测量需要测量系统灵敏度高、区分氡及其子体等特点,设计了静电累积法α能谱空气测氡仪。本论文首先阐述了空气中氡的α能谱测量理论基础,再从理论上证实和提出了静电累积法α能谱测量:使α辐射体被吸附到探测器表面,在其表面发生α衰变,这个α衰变产生的α粒子的能量基本上不会损耗在空气射程中,这样就能保持α射线能量线性特性,使α能谱测量成为可能。然后基于这一方法,设计了一款使用金硅面垒型半导体探测器的空气测氡仪。该静电累积法α能谱空气测氡仪是以单片微处理系统为核心,进行空气中α能谱数据采集与处理的综合应用系统,该数据采集系统能够完成α能谱数据的获取和分析的整个过程。该仪器利用大探测灵敏面积探测器以及大容积带静电氡气收集腔来提高测量灵敏度;采用温湿度同步测量来对氡浓度测量值进行修正,提高测量数据的准确性;通过α能谱测量,能有效的区分氡及其子体的能谱特性,能够分别测出氡子体218Po和214Po的α计数,提高了氡子体尤其是218Po的测量精度,从而确定空气中的氡浓度。本论文主要做了以下工作:选择仪器的探测元件,确定所要应用的测量原理;设计并调试低噪声信号调理电路、多道脉冲幅度分析器、微处理器系统、低功耗电源管理模块以及相应的软件系统;集成环境空气温湿度测量模块、实时时钟模块和最新OLED自发光显示屏;制作氡气收集装置,并将氡气收集装置和α能谱测量分析系统进行一体化设计;对仪器系统进行性能测试,发现不足并进行修改。经过标准氡室标定,得到该仪器的能量刻度曲线、能量分辨率、转换系数和测量灵敏度等重要信息,特别是测量灵敏度已经超过RAD7。实验数据表明静电累积法理论可行,仪器性能基本满足国家相关标准规定的对空气氡检测的要求。本论文中的静电累积法α能谱空气测氡仪可直接从显示屏读出测点空气氡浓度,适用于民用建筑工程室内辐射环境氡水平监测及污染控制、标准氡室氡浓度监测、矿井坑道及地铁氡浓度监测等领域,具有测量灵敏度高、结构简单合理、功耗低、体积小、重量轻、使用方便等优点。更多还原

【Abstract】 In recent years, radon hazards to human health have attracted wide attention, so air radon measurements become a popular technology for environmental monitoring. In this paper, author aims at the existing domestic and international air radon measurement methods and measuring instruments, and analyzes their deficiencies: The commonly used method for air radon measurement is the total amount measurement of radioactive particles, which is not able to distinguish between radon and its daughters. The existing radon monitors inαEnergy Spectrum, such as the RAD7 radon monitor inαEnergy Spectrum produced by the United States, use dynamic pumping way to collect radon gas, and then destroy the radon gas field balance in the measurement environment, so the measurement error will exist.In order to overcome the technical deficiencies of most of the air radon monitor, we design a kind of air radon monitor inαenergy spectrum based on static electricity accumulation method aiming at air radon concentration measurement requirements of high measurement sensitivity, ability of distinguishing between radon and its daughters.In this paper, the air radonαspectrum measurement theory is elaborated in the first. And then,αenergy spectrum measurement based on static electricity accumulation method is theoretically confirmed and proposed: Whenαradiator, which be adsorbed to the detector surface, decays on the surface of the detector surface, energy ofαparticles produced from theαdecay basically will not lose in the air, so thatαspectrum measurement is feasible. Based on this method, a kind of air radon monitor using gold silicon surface barrier semiconductor detector is designed.The air radon monitor inαenergy spectrum based on static electricity accumulation method, using a single-chip micro-processing system as its core, is a integrated applications system for acquisition and processing of theαenergy spectrum data. The data acquisition system can accomplish the whole process of acquisition and analysis of theαenergy spectrum data. We improve the measurement sensitivity of the instrument using the detector with large sensitive detect area and large volume electrostatic chamber of radon gas collection. The simultaneous measurements of temperature and humidity are used to modify the radon concentration measurement, so improve the accuracy of measurement data. Theαspectrometry measurement can effectively distinguish between radon and its daughters and measure respectivelyαcounts of radon daughters 218Po and 214Po, so especially increase 218Po measurement accuracy, and then the concentration of radon in air can be determined.The work is done as follow: The instrument detection device is selected. The application of measurement principle is determined. We designed and debugged low-noise signal conditioning circuit, multi-channel analyzer, microprocessor systems, low-power power management module and the corresponding software system. Environmental air temperature and humidity measuring module, real-time clock module and the latest self-luminous OLED display are integrated in the instrument. Radon gas collection device produced and theαenergy spectrum analysis system are integrated together. System performance of the equipment is test and the deficiencies found will be changed.After calibration of standard radon chamber, we get energy calibration curve, the energy resolution, conversion factors and measurement sensitivity and other important information of the instrument. In particular, it is found that measurement sensitivity of the instrument over RAD7 radon monitor. Through the analysis of experimental data, we can conclude that static electricity accumulation method is feasible, and instrument performance basically complies with the relevant national standard of radon detection in air.The air radon concentration in some point can be read directly from the display of air radon monitor inαenergy spectrum based on static electricity accumulation method. It applies to lots of fields, such as environmental radiation surveillance of civil engineering indoor radon levels, pollution control, radon concentration surveillance in standard radon chamber, and radon concentration surveillance in mine tunnels and Subway. It has the characteristics of high measurement sensitivity, simple structure, low power consumption, small size, light weight, being easy to operate.更多还原