Varying the aspect ratio of toroidal ion traps: Implications for design, performance, and miniaturization
Varying the aspect ratio of toroidal ion traps: Implications for design, performance, and miniaturization
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DOI：
10.1016/j.ijms.2021.116703
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发表时间：
2021-09-11
影响因子：
1.8
通讯作者：
Austin, Daniel E.
中科院分区：
文献类型：
--
作者：
Hettikankanange, Praneeth M.;Austin, Daniel E.
在小型化离子阱质谱仪中，大的纵横比（AR）导致更高的离子容量。离子阱的AR表示扩展捕获尺寸与特征捕获尺寸之间的比率。与线性和直线阱相反，改变环形离子阱（TorIT）的AR导致捕获电势的曲率和形状的程度的改变，并且因此导致作为质量分析器的性能的改变。SIMION模拟表明，捕获势中的高阶项对于小的和中等的AR值（低于类似于10）变化很大，对于较大的AR值，效果渐近平坦。由于电极几何形状的不对称性，陷阱中心与陷阱的几何中心不重合，并且该位移也随AR而变化。例如，在非对称TorIT中，俘获势中的鞍点和几何陷阱中心根据AR而在+0.6至-0.4mm之间变化。离子的长期频率也随着AR的变化而变化。而简化的TorIT中的离子对于任何AR值都具有稳定的轨迹，非对称TorIT中的离子在大的AR值处变得不稳定。高阶项、俘获中心和长期频率随AR的变化是环形陷波器的独特特征，并且当AR改变时，需要陷波器设计和操作的显著改变。(C)2021爱思唯尔有限公司版权所有。
A large aspect ratio (AR) leads to higher ion capacity in miniaturized ion trap mass spectrometers. The AR of an ion trap represents the ratio between an extended trapping dimension and the characteristic trapping dimension. In contrast to linear and rectilinear traps, changing the AR of a toroidal ion trap (TorIT) results in changes to the degree of curvature and shape of the trapping potential, and hence, on performance as a mass analyzer. SIMION simulations show that higher-order terms in the trapping potential vary strongly for small and moderate AR values (below similar to 10), with the effects asymptotically flattening for larger AR values. Because of the asymmetry in electrode geometry, the trapping center does not coincide with the geometric center of the trap, and this displacement also varies with AR. For instance, in the asymmetric TorIT, the saddle point in the trapping potential and the geometric trap center differ from +0.6 to -0.4 mm depending on AR. Ion secular frequencies also change with the AR. Whereas ions in the simplified TorIT have stable trajectories for any value of AR, ions in the asymmetric TorIT become unstable at large AR values. Variations in high-order terms, the trapping center, and secular frequencies with AR are a unique feature of toroidal traps, and require significant changes in trap design and operation as the AR is changed. (C) 2021 Elsevier B.V. All rights reserved.