【作者】 王宇天；

【导师】 李春生；

【作者基本信息】 吉林大学 ， 仪器科学与技术， 2024， 硕士

【摘要】 高分辨率二次离子质谱仪(High Resolution Secondary Ion Mass Spectrometry,HR-SIMS)是一种重要的表面分析仪器,具有高空间分辨率、高质量分辨率和高分析精度的微区原位同位素、元素分析能力,广泛应用于材料科学、海洋科学、能源科学和核科学等关乎国家经济和国防安全的领域,成为发展潜力较大的表面分析仪器之一。磁场分析器是HR-SIMS的重要部件,磁场稳定度要求严格,直接影响整台仪器的分析精度,准确测量实时磁场值并及时进行反馈控制对于整台仪器至关重要。本论文依托国家重点研发计划重点专项项目“高分辨率二次离子质谱仪研制”,项目计划研制一套HR-SIMS科学仪器,用于深海探测、深空探测、矿产勘探与晶格常数研究等领域。本论文旨在设计一套高稳定度磁场控制系统,使磁场分析器实现优于±20ppm的高磁场稳定度,保证二次离子流经过双聚焦质量分析器后进入接收器狭缝,高磁场稳定度将有利于整台仪器分析性能的提升。本文主要研究内容如下:1、双聚焦离子光学原理与磁场控制方法研究。理论研究双聚焦质量分析器能量发散和质量发散的影响条件,建立SIMION二次离子光学系统仿真模型,模拟不同磁场稳定度对离子运动轨迹的影响,验证磁场稳定度优于±20ppm的项目技术指标可行性。讨论常见磁场控制系统中控制结构、测量单元和控制算法的技术现状,综合考虑磁场稳定度技术指标和已有部件单元参数等因素,确定以磁场值反馈式控制结构、Hall探头与NMR探头相结合的测量单元和模糊PID算法为主体开发磁场控制系统。2、磁场控制系统硬件研制。研制测量单元,以四路规格相同的Tesla Tamer探头实时测量磁场值并向磁场控制器传输0～2.5V磁场值信号,以Metrolab PT2026探头定期校准Tesla Tamer探头。研制磁场控制器,包括配备24位模数转换器ADS1256的采集模块,配备XILIINX XC3S1500型FPGA芯片的控制模块,配备20位数模转换器AD5791的磁铁电源驱动模块,以及传输信号与电源的底板。实现从四路Tesla Tamer探头分别采集0～2.5V磁场值信号、运行模糊PID控制器、建立磁场控制器与主控PC端之间通信以及输出0～5V磁铁电源控制信号的硬件功能,驱动磁铁电源输出对应电流值,使磁场分析器产生对应磁场值。3、磁场控制系统软件开发。基于磁场控制器控制模块的FPGA芯片开发模糊PID控制器,建立输入隶属函数、控制规则和输出隶属函数等单元结构,引入适用于非线性被控对象的智能控制算法提升系统控制性能。开发基于LABVIEW平台的上位机软件系统,实现人机交互功能,包括管理隶属函数和控制规则等模糊控制参数的控制部分,以及实时显示四路Tesla Tamer探头磁场测量值和磁场波动程度的显示部分。4、磁场控制系统测试。集成硬件研制与软件开发内容,以Metrolab PT2026探头为基准校准Tesla Tamer探头,解决Tesla Tamer探头存在的时间漂移、温度漂移等问题。针对项目技术指标进行单独的磁场稳定度测试,进而开展HR-SIMS谱图测试,结果表明本系统磁场稳定度达到±6ppm,满足项目技术指标要求,所得质谱谱图形状良好,平顶峰较稳定,可以充分提供样品分析所需同位素信息。更多还原

【Abstract】 High Resolution Secondary Ion Mass Spectrometry(HR-SIMS)is an important surface analytical instrument with high spatial resolution,high mass resolution and high analytical accuracy for micro-area in-situ isotope and elemental analyses,which is widely used in the fields of material science,marine science,energy science and nuclear science,which are related to the national economy and national defence security.It is widely used in material science,marine science,energy science,nuclear science and other fields related to national economy and national defence security,and has become one of the surface analytical instruments with greater development potential.The magnetic field analyser is an important part of HR-SIMS,and the stability of magnetic field is required to be strict,which directly affects the analysis accuracy of the whole instrument,and accurate measurement of real-time magnetic field value and timely feedback control are crucial for the whole instrument.This thesis relies on the key special project " Development of High Resolution Secondary Ion Mass Spectrometry" of the National Key Research and Development Programme,which is planned to develop a set of HR-SIMS scientific instruments for deep ocean exploration,deep space exploration,mineral exploration and lattice constant research.The aim of this paper is to design a set of high stability magnetic field control system,so that the magnetic field analyser can achieve a high magnetic field stability better than ±20ppm,to ensure that the secondary ion flow through the double focusing mass analyser into the receiver slit,and the high magnetic field stability will be conducive to the enhancement of the analytical performance of the whole instrument.The main research content of this paper is as follows:1.Research on the principle of double-focus ion optics and magnetic field control method.Theoretically study the influence conditions of energy dispersion and mass dispersion of double-focusing mass analyser,establish simulation model of SIMION secondary ion optical system,simulate the influence of different magnetic field stability on ion trajectory,and verify the feasibility of the technical index of magnetic field stability better than ±20ppm in the project.Discuss the current status of control structure,measurement unit and control algorithm in common magnetic field control systems,and consider the magnetic field stability technical index and existing component unit parameters,etc.,and determine to develop the magnetic field control system with the magnetic field value feedback control structure,the measurement unit combining Hall probe and NMR probe,and the fuzzy PID algorithm as the main body.2.Development of magnetic field control system hardware.The development of the measurement unit,four-way Tesla Tamer probe with the same specifications of realtime measurement of the magnetic field value and the magnetic field controller to transmit the 0 ～ 2.5V magnetic field value signal to the Metrolab PT2026 probe regular calibration of the Tesla Tamer probe.Development of the magnetic field controller,including an acquisition module equipped with a 24-bit analogue-to-digital converter ADS1256,a control module equipped with a XILIINX XC3S1500-type FPGA chip,a magnet power supply driver module equipped with a 20-bit digital-to-analogue converter AD5791,and a backplane for transmitting the signals and power supply.The hardware functions of collecting 0～2.5V magnetic field value signals from the four Tesla Tamer probes,running the fuzzy PID controller,establishing communication between the magnetic field controller and the master PC,and outputting 0～5V magnet power supply control signals are implemented to drive the magnet power supply to output the corresponding current value,so as to enable the magnetic field analyser to generate the corresponding magnetic field value.3.Development of magnetic field control system software.Develop fuzzy PID controller based on the FPGA chip of the magnetic field controller control module,establish the unit structure of input affiliation function,control rules and output affiliation function,and introduce intelligent control algorithms applicable to nonlinear controlled objects to improve the system control performance.The upper computer software system based on the LABVIEW platform is developed to realise the humancomputer interaction function,including the control part that manages the fuzzy control parameters such as the affiliation function and the control rules,and the display part that displays in real time the magnetic field measurements and the magnetic field fluctuation degree of the four Tesla Tamer probes.4.Magnetic field control system testing.Integrating hardware development and software development,the Tesla Tamer probe was calibrated using the Metrolab PT2026 probe as a reference to solve the problems of time drift and temperature drift of the Tesla Tamer probe.A separate magnetic field stability test was carried out for the project specifications,and then the HR-SIMS spectrum test was carried out,which showed that the magnetic field stability of the system reached ±6ppm,meeting the requirements of the project specifications,and the resulting mass spectrum had a good shape with a stable flat-top peak,which could fully provide the isotope information required for the analysis of the samples.更多还原