Zhang J, Enke C G
Department of Chemistry, University of New Mexico, Albuquerque 87131, USA.
J Am Soc Mass Spectrom. 2000 Sep;11(9):759-64. doi: 10.1016/S1044-0305(00)00145-8.
A new cylindrical ion mirror has been designed to create an electric field that is non-linear or curved along the flight path axis for general-purpose time-of-flight mass spectrometers. The inclusion of one or two grids is found to improve the radial field homogeneity especially around the aperture. Only three cylindrical electrodes are used in the design. Changing the electrode dimensions and voltages affects the electric field distribution. Once the electrode dimensions are fixed, there are only two adjustable parameters for achieving optimum nonlinear electric field shape. Resolving powers of 7,000 and 16,100 have been achieved with kinetic energy variations of 34 and 10.5%, respectively. Simulations show that the electric field homogeneity in the radial direction enables the use of ion beam diameters up to 15 mm with only modest loss of resolving power. Increasing the mirror diameter could further increase the practical ion beam diameter. This article details the electric field distribution within the cylindrical mirror in both axial and radial directions. The voltages of the middle and rear electrodes affect the resolving power and the kinetic energy range over which focus can be achieved. The predicted arrival time spread for a single m/z value is narrower than that caused by the turn-around time of ions in a gas-phase ion source. In this case, the broad energy range over which good focus is achieved enables the use of higher extraction fields for turn-around time reduction.
一种新型圆柱形离子镜已被设计出来，用于为通用飞行时间质谱仪创建一个沿飞行路径轴呈非线性或弯曲的电场。发现包含一个或两个栅格可改善径向场均匀性，尤其是在孔径周围。该设计中仅使用了三个圆柱形电极。改变电极尺寸和电压会影响电场分布。一旦电极尺寸固定，实现最佳非线性电场形状仅有两个可调参数。分别在动能变化34%和10.5%的情况下，实现了7000和16100的分辨率。模拟表明，径向的电场均匀性使得能够使用直径达15毫米的离子束，而分辨率仅有适度损失。增大镜直径可进一步增大实际离子束直径。本文详细介绍了圆柱形镜内轴向和径向的电场分布。中间和后部电极的电压会影响分辨率以及能够实现聚焦的动能范围。对于单个质荷比（m/z）值，预测的到达时间展宽比气相离子源中离子转向时间所导致的展宽更窄。在这种情况下，能够实现良好聚焦的宽能量范围使得可以使用更高的提取场来减少转向时间。
