高分辨本领飞行时间质量分析器的设计

在飞行时间质谱仪中,被测离子的能量分散是影响仪器分辩本领的重要因素。离子反射器是减小这一因素影响、提高分辩本领的强有力工具。本文设计了两种二级场式离子反射器,放置于直线管和V形管的质量分析器内并使用计算机离子光学软件模拟了分析器体系在离子能量分散为100eV时,其分辩本领分别可达5700和16000.     

飞行时间质谱和高性能电子学控制技术

飞行时间质量分离器是飞行时间质谱仪的主要组成部分。飞行时间质谱（TOF MS）具有分析质量范围宽、分析速度快、仪器结构简单等优点,但离子初始动能和初始位置容易分散是影响其分辨率的核心因素。本综述根据本课题组多年的研制经验,着重介绍离子束垂直引入方式的反射式有栅网飞行时间质谱的离子光学以及相关电子学控制的核心技术原理。离子光学核心技术涉及到离子加速场和离子反射场的机械加工控制和精密装配控制等,电子学控制核心技术主要包括高压电源和高压脉冲电源的精密制作。     

激光致等离子体中离子引出的空间

对于原子法激光分离同位素(AVLIS),离子引出的特性研究具有十分重要的意义。采用YAG脉冲激光的四倍频输出与两平行平面极板间空气相互作用产生等离子体。极板间加几百伏电压,使离子从极板间的等离子体中引出。采用特殊设计的极板结构和实验装置,研究了电荷收集量在极板上的分布。通过对数据的分析,总结了离子引出过程中等离子体扩散效应,并发现离子引出的空间分布与极板间距有关,而与极板间电压基本无关。     

光离子化检测器的电离室结构设计与实验分析

文中设计了光离子化检测器,利用Simion8.1软件进行了不同极板电压、极板间距以及载气入气口直径下的静电场仿真,在尽可能小的气室体积内设计出了结构更加优异的电离室,同时通过仿真分析降低了大量试验时间与成本。通过仿真与分析,得到了极板电压与带电粒子收集效率的关系,确定了175 V的极板电压以及收集板与极板间距为6 mm,入气口直径为6 mm。在系统实验阶段,对通入气体的流速做了优化,测试中气体流速为200 mL/min;对0～273 ppm的异丁烯气体进行检测,系统响应与气体浓度间成良好的线性关系,拟合优度为0.986 61,在不同时间段检测系统具有良好的稳定性和可重复性。     

新型飞行时间质谱离子移除装置的研制

本文介绍了一种用于飞行时间质谱离子检测器选择性移除非目标检测离子的脉冲电场装置。通过调节脉冲电压时序、优化脉冲电压值,实现对非目标检测离子的有效移除,使离子选择性地进入离子检测器,减少离子检测器的消耗,延长其使用寿命。结果表明,除了由脉冲上升沿和下降沿引起的质谱信号振荡对相邻飞行时间区域内的离子产生一定的影响外,该装置和方法可以选择性地、有效地移除非目标检测离子,以减少MCP离子检测器的消耗,延长其使用寿命,为飞行时间质谱非目标离子的移除提供一种简单、可行的方法。     

一种射频微机械可变电容的设计与优化

提出了一种高Q值、宽调节范围的凹型结构微机械可变电容.它由4个(3对)极板构成,其中一对为电容极板,另外两对为控制极板.RF信号通过电容极板传输,而直流控制电压则施加在控制极板上.使用HFSS软件对该电容进行了结构仿真及优化,得到最大Q值为171(1.6GHz).结构优化后,调节范围为15.6,并设计了该电容的工艺流程,具有工艺简单、易与标准的IC电路集成等优点.     

高能量离子束诊断质谱仪的研制及性能表征

本研究开发了一台应用于高能量离子束诊断的直线式飞行时间质谱仪,实现了其与高能真空弧放电离子源的联用。该仪器加速电压30 kV,飞行腔有效飞行距离1.5 m,通过短脉冲离子门精确截取,ICCD高速相机优化聚焦,仪器分辨率优于90 FWHM,对放电过程中产生的等离子体可实现不同时间的离子成分分析。将该方法用于真空弧放电离子源放电过程中离子成分的检测,放电2 μs时,电离成分以气态离子C⁺、O⁺、C²⁺、O²⁺为主;放电6 μs后,除气体成分外,还可以检测到Fe⁺、Cu⁺及其同位素金属离子峰。该仪器能够给出离子源放电产生离子的种类、价态以及相对含量等信息,可实现整个放电过程产生离子成分信息的准确诊断。     

加速器质谱(AMS)测量中充气飞行时间探测方法研究

为了提高加速器质谱 (AMS)测量中同量异位素的分辨能力 ,设计了一种新型探测器即充气飞行时间探测器。主要探讨了充气飞行时间谱仪 (GF-TOF)的原理、结构和测试方法 ,给出了用α源调试的结果。通过增加离子的能量并合理选择气体和飞行距离提高 GF-TOF对同量异位素的分辨能力     

飞行时间质谱的离子峰形模拟分析方法和应用

飞行时间质谱的离子峰形中包含了离子产生时的速度分布和空间分布信息，了解速度和空间分布对离子峰形的影响，可以根据峰形推测离子的产生机理。运用概率密度理论建立了一套飞行时间质谱的峰形模拟的方法和程序，并通过模拟分析考察了不同的空间分布和速度分布对离子峰形的影响。在偏离空间聚焦条件下，离子峰形显示了空间分布的信息。     

用于双聚焦磁质谱仪的电子轰击离子源的设计与研究

本文设计了一种用于双聚焦磁质谱仪的电子轰击离子源,运用静电透镜软件simion的仿真模拟研究了它的离子光学系统,研究了离子光学系统电压参数和离子束的初始半散角对拉出离子效率和离子束宽度的影响.     

A photoelectron-photoion coincidence imaging apparatus for femtosecond time-resolved molecular dynamics with electron time-of-flight resolution of sigma=18 ps and energy resolution Delta E/E=3.5%

We report on the construction and performance of a novel photoelectron-photoion coincidence machine in our laboratory in Amsterdam to measure the full three-dimensional momentum distribution of correlated electrons and ions in femtosecond time-resolved molecular beam experiments. We implemented sets of open electron and ion lenses to time stretch and velocity map the charged particles. Time switched voltages are operated on the particle lenses to enable optimal electric field strengths for velocity map focusing conditions of electrons and ions separately. The position and time sensitive detectors employ microchannel plates (MCPs) in front of delay line detectors. A special effort was made to obtain the time-of-flight (TOF) of the electrons at high temporal resolution using small pore (5 microm) MCPs and implementing fast timing electronics. We measured the TOF distribution of the electrons under our typical coincidence field strengths with a temporal resolution down to sigma=18 ps. We observed that our electron coincidence detector has a timing resolution better than sigma=16 ps, which is mainly determined by the residual transit time spread of the MCPs. The typical electron energy resolution appears to be nearly laser bandwidth limited with a relative resolution of DeltaE(FWHM)/E=3.5% for electrons with kinetic energy near 2 eV. The mass resolution of the ion detector for ions measured in coincidence with electrons is about Deltam(FWHM)/m=14150. The velocity map focusing of our extended source volume of particles, due to the overlap of the molecular beam with the laser beams, results in a parent ion spot on our detector focused down to sigma=115 microm.     

小型飞行时间质谱装置的构建

飞行时间质谱仪（TOF MS）在准确度、分辨率、灵敏度、质量上限、分析速度等方面具有优势,在生命科学等领域发挥着重要作用。目前商用飞行时间质谱仪已经比较成熟,但仪器尺寸普遍较大,且价格昂贵,维护困难;而小型仪器则面临分辨率较低等问题。提高小型飞行时间质谱仪的分辨率,降低购置成本和维护成本,对于飞行时间质谱仪的大范围推广有着重要意义。本工作构建了一套分辨率较高的小型飞行时间质谱装置,包括真空系统、离子源、锥孔、引出加速及偏转模块、离子反射镜模块、探测器模块、电路系统等。该仪器主体尺寸较小（0.5 m×0.5 m×0.7 m）,飞行管长度仅0.25 m。由于采用了模块化设计思路,各个模块之间独立封装,仪器的维护、升级工作简单易行。该仪器的关键模块采用创新设计,使得在m/z 2 000处分辨率可达4 200。     

自动富集-单光子电离质谱在线测量氯酚的研究

氯酚类化合物是垃圾焚烧所产生的二噁英前生体之一,对二噁英的浓度有很好的指示作用。针对气相中氯酚类二噁英前生体的在线连续监测,自行研制了全自动富集进样-单光子电离-反射式飞行时间质谱仪。为实现低浓度氯酚的检测,设计了全自动的富集进样系统,利用3根阵列式Tenax TA吸附管,结合全自动控制的高温电磁阀,实现了气体样品连续自动的“富集 热解析-质谱进样”。研制的反射式单光子电离-飞行时间质谱仪采用10.6 eV真空紫外灯作为光电离源,对气体样品分子进行软电离,避免了碎片离子的产生,所获得的样品分子离子经反射式飞行时间质量分析器完成检测,仪器分辨率达到3 000（m/z 78）。以3种典型的二噁英前生体氯酚类化合物（邻氯苯酚、2,4-二氯苯酚、2,4,6-三氯苯酚）为检测对象,对该仪器性能进行考察。富集进样系统对3种氯酚类化合物的富集倍数分别达到60、249、503,检测限分别达到66、120、125 pg/L,动态线性范围分别为166 pg/L~16.6 ng/L、210 pg/L~21 ng/L、255 pg/L~25.5 ng/L。这些研究结果为今后开展垃圾焚烧烟气中二噁英的现场连续监测工作奠定了基础。     

Large area mass analyzer instrument for the chemical analysis of interstellar dust particles

A new instrument to analyze the chemical composition of dust particles in situ in space has been developed. The large target area ( approximately 0.2 m(2)) makes this instrument well suited for detecting a statistically significant number of interstellar dust grains or other dust particles with a low flux. The device is a reflectron-type time-of-flight mass spectrometer that uses only flat electrodes for the generation of the parabolic potential. The instrument analyzes the ions from the impact generated plasma due to hypervelocity dust impacts onto a solid target surface. The SIMION ion optics software package is used to investigate different potential field configurations and optimize the mass resolution and focusing of the ions. The cylindrically symmetric instrument operates with six ring electrodes and six annular electrodes biased to different potentials to create the potential distribution of the reflectron. The laboratory model of the instrument has been fabricated and tested. Hypervelocity dust impacts are simulated by laser ablation using a frequency doubled Nd:YAG laser with approximately 8 ns pulse length. The experimental data show typical mass resolution m/Deltam approximately 200.     

A compact gridless channel plate detector for time-of-flight measurements

A compact channel plate detector used as a start detector in heavy ion reaction studies is described. In order to avoid spurious structures in the energy spectra of the detected ions the usual electron accelerating grid is replaced by five electrodes which provide a uniform electric field. The start detector has an intrinsic resolution of 85 ps and efficiency of 90% for medium mass nuclei. The overall time resolution with a solid state detector as stop is 105 ps.     

Design and performance evaluation of a novel square ion trap with mass analysis in the radial a axial directions

A novel three-dimensional square ion trap is reported as a mass analyzer or an ion transfer device. The square ion trap was constructed with six square planar electrodes while the electric field was optimized by changing their relative positions to arrange the strength of higher-order fields. Ion trajectory simulations demonstrate the square ion trap efficiently operates with radial and axial excitation. Additionally, ions ejected from the radial direction contained lower kinetic energies and their energy distribution were more centralized. These properties may improve the ion transfer efficiency.     

丙酮-辅助光电离离子迁移谱检测TATP炸药的研究

三过氧化三丙酮(TATP)是一种新型过氧化物炸药,由于制备原料易得、制备方法简单,常被恐怖分子用于恐怖袭击等犯罪活动中。本工作以25mg/L丙酮作为掺杂剂,发展了一种基于丙酮-辅助光电离离子迁移谱检测TATP的方法。对电场强度和进样口温度等参数进行优化后,TATP的线性范围为5~100ng,检测限可达1.2ng。利用飞行时间质谱对反应试剂离子和产物离子进行分析,确定反应试剂离子主要是丙酮二聚体离子[(CH3)2CO]2H+,产物离子为TATP的碎片离子m/z91[(CH3)2C(O)OO]H+。实验结果表明,这种新型非放射性电离源离子迁移谱能够实现痕量TATP过氧化物爆炸物的高灵敏检测。     

Evaluation of major historical ICR cell designs using electric field simulations

In Fourier-transform ion cyclotron resonance mass spectrometry, ions are detected by measuring image current induced in the detecting electrodes by trapped ions rotating in a magnetic field at their cyclotron frequencies. The ion trap used for this purpose is called the Penning trap. It can have various configurations of electrodes that are used to create a trapping electric field, to excite cyclotron motion, and to detect the induced signal. The evolution of this type of mass spectrometry is mainly driven by progress in the technology of superconducting magnets and in the constantly improved design of the ion cyclotron resonance (ICR) measuring cell. In this review, we focus on ICR cell designs. We consider that the driving forces of this evolution are the desire to increase resolution, mass accuracy and dynamic range, as well as to adapt new methods for creating and trapping ions.