基于介电剖面法的极地冰芯电学性质测量机理与技术优化研究

The polar ice sheet keeps the significant information of history of global climatic revolution. It has a vital meaning for understanding global climatic variation by polar ice core drilling and analysis. At present, the Chinese polar deep ice core drilling project is in the initial stage. And the ice core measuring methods are immature. The available approaches have certain disadvantages. An ice core in situ measuring approach of non-destructive and high-resolution is urgently needed to obtain the inner substance composition and content of ice core rapidly and accurately. The mechanism and technical optimization of polar ice core property measuring based on dielectric profiling method have been researched in the project of application. The research content includes technical matters research, for example, mechanism of polar ice core conductivity and permittivity measuring using dielectric profiling method, frequency selection of alternating excitation electric field during measuring process, computation of potential distribution between two electrodes, and analysis of dielectric properties of dielectric medium. The research content also includes technical optimization research, for example, eliminating of external error source like stray capacitance and charge exchange between electrodes and ice core. The measuring of preparative ice samples of different properties will be carried out by using designed front-end equipment. And the corresponding relationship between electrical parametric variation and ice sample properties will be analyzed and interpreted. Through the research presented above, the rationality of principle of applying the method to measure the polar ice core and the dependability of equipment design could be proved. The research findings will establish the theoretical and technical foundation for subsequent development of our Chinese polar ice core dielectric profiling device.

极地冰盖记录着地球气候演变历史的重要信息，对其进行钻探取芯，进行冰芯研究对人类了解全球气候变化意义重大。目前我国极地深冰芯钻探工程刚刚起步，对冰芯的测试手段还不成熟，现有方法存在着一定弊端，我们急需一种现场原位、无损的、高分辨率的冰芯测试方法，以快速准确地获取冰芯内部物质组成及含量。该申请项目着重研究基于介电剖面法的极地冰芯性质测量机理与技术优化。研究内容包括应用介电剖面法测试极地冰芯电导率及电容率的测试机理，以及测试过程中交变激励电场频率的选择、电极间电位分布的计算、电介质介电特性的分析等技术问题研究，还包括前端设备消除寄生电容、消除电极与冰芯间局部电荷交换等外部误差源等的技术优化的研究，通过设计的前端设备对制备的不同性质冰样进行测试，分析解释电学参数变化与冰样性质的对应关系，验证该方法测试极地冰芯原理的合理性及设备设计的可靠性，为后续研制我国自己的冰芯介电剖面仪奠定理论与技术基础。

针对极地地区的研究对了解全球气候的变化有着至关重要的意义，分析极地冰芯可以获取地球古气候演变的重要信息。针对基于介电剖面法对极地冰芯电学性质进行测试机理的研究，为现场原位、无损地测量冰芯提供一种合理、高效、高精度的测量手段和理论研究基础，为极地冰芯分析提供技术依据。课题对介电剖面法测试极地冰芯电学特性的测试机理、冰芯介电剖面分析仪测试设备的设计与技术优化进行了研究，并且应用设计的冰芯介电剖面测试仪对空气电容、标准电阻电容以及模拟冰样进行测试试验。通过对冰芯电学性质的介电剖面法测试机理的深入研究，确定应用电容测试原理，将冰芯作为电介质，运用扫描电极测试冰芯电导率及电容率方法的可行性；通过设计保护电极及电极表面氧化镀膜处理等优化设计，有效地消除了误差对测试结果造成的影响；通过设计信号抗干扰保护装置，有效地屏蔽了外界干扰，实现了信号稳定、准确输出；通过对设备进行的包括空气电容测试、标准电阻、电容测试、模拟冰芯样品测试以及实际冰芯测试，测得空气电容值为62fF—65fF之间，符合63.4fF的计算空气电容值，电导率测量精度≤0.5%，电容率测量精度≤0.8%，极地冰芯电容实测值为为110fF至130fF之间，测试结果验证了设计的冰芯介电剖面测试仪具有很高的工作稳定性、测试精度以及灵敏度，符合设计要求。设计加工的冰芯介电剖面测试仪硬件系统具有结构简洁、运行稳定、易操作，功能齐备等特点；软件系统具有界面友好、信号采集精准、采样频率高、灵敏度高等特点。该项目所研究的内容以及研发的冰芯介电剖面测试仪为国内首创，填补了我国在该技术上的空白，研究成果将为后续在南极昆仑站深冰芯钻探现场测试冰芯提供了必要的技术保证。