质子转移反应质谱仪聚焦型漂移管的设计及仿真研究

漂移管是质子转移反应质谱仪（PTR-MS）的核心部件之一，对漂移管进行技术创新是改善仪器性能的重要途径。近年来，聚焦型漂移管（focusing drift tube, FDT）因具有离子利用率高的优点逐渐被重视。本研究报道了一种结合射频四极杆及电阻玻璃管的聚焦型漂移管的设计与仿真，四极杆用于提供射频聚焦场，电阻管用于产生均匀分布的直流梯度电场。基于设计的3D结构，在SIMION 8.1中构建仿真模型，采用m/z 19、55和100等3种离子对四极杆的杆体直径、射频场频率及电压幅值等参数进行系统性探究。结果表明，射频场的引入对减小离子束半径非常有效，较大直径的杆体有利于提高装置的聚焦能力，特别是对于低质荷比离子。当频率约2 MHz时，聚焦效率最高，随着电压幅值的提高，离子束半径迅速减小，随后逐渐趋平。另外，超过85%的离子能够顺利透过直径为1.0 mm的采样孔，传输效率比传统漂移管提升了约28倍。该研究对射频四极杆聚焦型漂移管（RFQ-FDT）的结构设计、SIMION建模及离子透射率均做了详细阐述，可为装置的实际应用提供一定的理论支持。

Design and Simulation of Focusing Drift Tube for Proton Transfer Reaction Mass Spectrometer

Drift tube is one of the core components of proton transfer reaction mass spectrometer (PTR-MS). Technical innovation of the drift tube is one of the important ways to improve the performance of the instrument. In recent years, focusing drift tube (FDT) has been paid more and more attention because of its high ion utilization ratio. In this work, the design and simulation of a FDT combined with a radio frequency quadrupole and a resistor glass tube was reported. The quadrupole was used to provide an RF focusing field, and the resistor glass tube was used to generate a uniformly distributed DC gradient electric field. Based on the designed 3D structure, the simulation model was built in SIMION 8.1 and the parameters such as the diameter of the quadrupole, the frequency and the voltage amplitude of the RF field were simulated systematically with three kinds of ions (m/z 19, 55 and 100). The results showed that the introduction of the RF field was very effective in reducing the radius of the ion beam, and the rod with larger diameter was beneficial to improve the ion focusing efficiency, especially for the ions with low mass-charge ratio. When the frequency was about 2 MHz, the focusing efficiency was the highest. With the increase of the voltage amplitude, the radius of ion beam decreased rapidly and finally tended to smooth. In addition, more than 85% of the ions could successfully pass through the sampling orifice with a diameter of 1.0 mm, and the transport efficiency was about 28 times higher than that of the traditional drift tube. In this study, structural design, SIMION modeling and ion transmittance of RF quadrupole focusing drift tube (RFQ-FDT) were described in detail, hoping to provide some technical support for follow-up research.