基于高场非对称离子迁移谱的糖类异构体分离研究

本工作研发了一款配套滤波算法及重叠峰分离算法、可独立使用的平板型高场非对称离子迁移谱(FAIMS)系统,能够在分离不同离子、有效滤噪的同时,从重叠峰中准确、快速提取分析物峰,由此实现物质的精准定性分析。通过评估该FAIMS装置对糖类异构体的分离效果,发现FAIMS能有效分离出蔗糖离子的2种结构,证明其对离子结构差异更加敏感。采用氮气、氦气的混合气体作为载气,可进一步提高FAIMS的分辨力。当氦气比例达到40%时,蔗糖峰和麦芽糖峰的重合度由纯氮气时的77%降低至50%。本研究表明,该FAIMS系统可为同分异构体的定性分析提供一种新方法。     

高场不对称波形离子迁移谱关键测控模块研究

研究了高场不对称波形离子迁移谱(high-field asymmetric waveform ion mobility spectrometer,FAIMS)两个关键测控模块:波形不对称高压产生模块和微弱电流检测模块的设计。通过采用反激升压原理,设计了一种电压幅度在线可调的波形不对称高压产生电路模块,其输出电压峰峰值达1 800 V,频率达1 MHz;微弱电流检测采用超高电阻反馈式I-V转换电路,并对失调电压进行补偿,同时结合PCB割板处理及包裹屏蔽等抗干扰措施,使得微弱电流模块的检测下限优于0.1 pA。最后,通过对比实验研究了不同波形不对称高压与分离效果关系,并以苯为样品对系统的检测下限进行了研究,结果表明采用上述测控模块的FAIMS检测下限达1×10-9。     

A laser spectrometer of field-asymmetric ion mobility

A method for analyzing a substance has been experimentally tested. The method combines the field-asymmetric ion mobility spectrometry and laser ionization of molecules under atmospheric pressure. Pulsed radiation of the fourth harmonic of an YAG: Nd³⁺ laser (λ = 266 nm) and a spectrometer with a cylindrical analysis camera were used. The results of detecting nitrocompounds—trinitrotoluene, cyclotrimethylenetrinitramine (hexogen, RDX), etc.—are presented. The experimental detection limits of the spectrometer are 5 × 10⁻¹⁵ g/cm³ (cyclotrimethylenetrinitramine) and ≤3 × 10⁻¹⁵ g/cm³ (trinitrotoluene).     

微处理器控制的离子迁移计样机的研制

介绍了离子迁移计的基本原理;概述了一种微处理器控制的离子迁移计样机的设计,包括总体结构、信号采集方法和主程序流程;给出了用本仪器测得的二氯二乙硫醚的负离子信号谱图.离子迁移计的灵敏度很高,可以应用于环境监测和化学侦察.     

离子迁移谱仪的温度与流量控制系统设计与实现

离子迁移谱检测仪通过分析不同物质的迁移率实现对被检物的鉴别,而物质的迁移率与温度、气压、电场条件密切相关,因此仪器在工作过程中需要对温度和气体流量等参数进行精确地实时控制。针对嵌入式离子迁移谱仪的应用要求,在ARM+嵌入式Linux系统架构下,利用ARM处理器的PWM功能,并对传统PID控制算法进行改进,设计了一种基于ARM的多路温度和流量控制系统,可以实现对温度及流量的快速而精确的实时控制,结构简单、可靠性高。     

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.     

基于脉冲电晕放电电离源的离子迁移谱仪设计与实现

针对传统直流电晕放电离子迁移谱仪(CD-IMS)稳定性差、功耗高的不足,设计制备了针-针结构脉冲电晕放电电离源,并使用该电离源搭建了脉冲CD-IMS装置。研制的高压脉冲发生电路输出幅值和脉冲重复周期可调,体积小、功耗低。研究了放电稳定性并进行了实际样品测试,在无离子门的情况下得到了正、负离子模式反应离子峰谱图。该装置在正负模式下的分辨率分别为25.17(甲基磷酸二甲酯(DMMP)二聚体)和15.88(水杨酸甲酯)。     

Noncontact measurement of electrostatic fields: verification of modeled potentials within ion mobility spectrometer drift tube designs

The heart of an ion mobility spectrometer is the drift region where ion separation occurs. While the electrostatic potentials within a drift tube design can be modeled, no method for independently validating the electrostatic field has previously been reported. Two basic drift tube designs were modeled using SIMION 7.0 to reveal the expected electrostatic fields: (1) A traditional alternating set of electrodes and insulators and (2) a truly linear drift tube. One version of the alternating electrode/insulator drift tube and two versions of linear drift tubes were then fabricated. The stacked alternating electrodes/insulators were connected through a resistor network to generate the electrostatic gradient in the drift tube. The two linear drift tube designs consisted of two types of resistive drift tubes with one tube consisting of a resistive coating within an insulating tube and the other tube composed of resistive ferrites. The electrostatic fields within each type of drift tube were then evaluated by a noncontact method using a Kelvin-Zisman type electrostatic voltmeter and probe (results for alternative measurement methods provided in supplementary material). The experimental results were then compared with the electrostatic fields predicted by SIMION. Both the modeling and experimental measurements reveal that the electrostatic fields within a stacked ion mobility spectrometer drift tube are only pseudo-linear, while the electrostatic fields within a resistive drift tube approach perfect linearity.     

Secondary ion quadrupole mass spectrometer for depth profiling--design and performance evaluation

A quadrupole-based secondary ion mass spectrometer designed for depth profiling is described which combines ultrahigh vacuum construction with high sputtering rate, detection sensitivity, depth resolution, mass spectral purity, and abundance sensitivity. Impurities such as B and Al implanted in Si can be profiled to levels below one part per million atomic (ppma), at a depth resolution equal to that obtained by commercial ion microprobes. The primary beam consists of 5-keV, mass-analyzed (40)Ar(+) ions, focused to about 70 microm in diameter. Its high current density (>25mA/cm(2)) permits adequate beam rastering and electronic signal-gating to optimize depth resolution. A secondary ion extraction lens and spherical energy filter are responsible for achieving abundance sensitivities of five to six orders of magnitude on the low mass side of a matrix peak. The ultrahigh vacuum environment of the sample dramatically reduces molecular peaks containing H, C, and O, allowing even hydrogen to be profiled to concentrations below 10 ppma. Because large amounts of data are generated by multi-element depth profiling, means for automated instrument control and data acquisition have been developed.     

Characterization of a single electrode focusing lens for ion beam deceleration

An ion beam deceleration system was studied for the high-current ion implanter at the Laboratório de Aceleradores e Tecnologias de Radiação at the Campus Tecnológico e Nuclear, of Instituto Superior Técnico. The installed system consists of a target plate and one electrostatic focusing lens with one electrode. This article describes the results of the evaluation of the new system. With this upgrade, the ion implanter provides enhanced versatility for decelerating to 5 keV a high current ion beam at the µA level. This implantation provides a wide area and allows for a continuous magnetic beam scanning, extending the energy range to lower values, opening up a wider set of applications.     

小型质谱仪离子源电路的设计

设计了一种适用于小型质谱仪离子源的控制电路,具有体积小、重量轻、效率高等优点,提供了三路可调的±250V离子透镜电压,通过检测电子发射电流来稳定灯丝电流的方式,满足了仪器高灵敏度、高稳定度的使用要求。