An asymmetric trapping field was generated from an asymmetric half-round rod electrode linear ion trap (A-HreLIT), and its performance of unidirectional ion ejection was studied. Two different asymmetric structures of A-HreLITs were constructed, one rotating y electrode pairs toward an x electrode with an angle θ, and the other stretching one x electrode with a distance α. The center of trapping field was displaced away from the geometrical center of the ion trap, defined to be the midpoint along the axis of y between x electrodes, which leads to unidirectional ion ejection through one x electrode. Computer simulations were used to investigate the relationship between asymmetric geometric parameter of θ (or α) and analytical performance. Both structures could result in similar asymmetric trapping fields, which mainly composed of dipole, quadrupole, and hexapole fields. The dipole and hexapole fields were approximately proportional to the asymmetric geometric parameter of rotation angle θ (or stretch distance α). In simulation, ion trajectories and ion kinetic energy were calculated. For ions with m/z 609 Th, the simulation results showed that mass resolution of over 2400 (FWHM) and ion unidirectional ejection efficiency of nearly 90% were achieved in an optimized A-HreLIT. Ion detection efficiency of A-HreLIT could be improved significantly with only one ion detector, while maintaining a considerable mass resolution. Furthermore, the A-HreLIT could be driven by a traditional balanced RF power supply. These advantages make A-HreLIT suitable for developing miniaturized mass spectrometer with high performance.

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从一个不对称的半圆形棒状电极线性离子阱（A-HreLIT）产生了一个不对称的俘获场，并研究了其单向离子喷射的性能。构造了两种不同的A-HreLITs不对称结构，一个旋转的y电极对朝着一个x电极以一个角度θ旋转，另一个旋转了一个x电极以一个距离α进行拉伸。俘获场的中心偏离离子阱的几何中心，其定义为x电极之间沿y轴的中点，从而导致通过一个x的单向离子喷射电极。使用计算机仿真来研究θ（或α）的不对称几何参数与分析性能之间的关系。两种结构都可能导致相似的不对称俘获场，其主要由偶极子场，四极子场和六极子场组成。偶极和六极场与旋转角θ（或拉伸距离α）的不对称几何参数大致成比例。在仿真中，计算了离子轨迹和离子动能。对于m / z的离子609 Th，模拟结果表明，在优化的A-HreLIT中，可以实现2400的质量分辨率（FWHM）和近90％的离子单向喷射效率。仅使用一个离子检测器，就可以显着提高A-HreLIT的离子检测效率，同时保持相当大的质量分辨率。此外，A-HreLIT可以由传统的平衡RF电源驱动。这些优点使A-HreLIT适用于开发高性能的小型质谱仪。

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