Ion Trap RF Field Balancing via Asymmetric Electrode Geometry
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Solution Overview
Problem
Ion trap devices face performance issues due to unbalanced centerline potentials caused by ejection slots, leading to non-linear field characteristics, which affect ion injection efficiency and mass bias during analysis.
Innovation Solution
The ion trap is 'stretched' in the X-axis direction by increasing the X electrode separation distance, and RF signals with non-matching voltage levels are applied to the Y and X electrodes to compensate for the ejection slots, achieving a balanced potential at the centerline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the ion trap is stretched in the X-axis direction to compensate for ejection slots, then non-linear field components are minimized, but the centerline potential becomes unbalanced
Solution Approach 1:
The patent applies parameter changes by using non-matching RF signal voltage levels on X and Y electrodes. Specifically, the X electrodes receive an RF signal with a higher voltage amplitude than the Y electrodes, which compensates for the asymmetric geometry introduced by stretching the ion trap in the X-axis direction. This parameter adjustment restores the centerline potential balance while maintaining the linear field characteristics achieved through the stretched configuration.
2Adaptability or versatility
If ejection slots are added to scan ions out of the trap, then mass analysis capability is enabled, but non-linear field characteristics are introduced
Solution Approach 1:
The patent applies asymmetry in two ways: first, by introducing asymmetric ejection slots in the X electrodes to enable mass analysis capability; second, by compensating for the resulting asymmetric field distortion through asymmetric RF signal voltage levels (higher voltage on X electrodes than Y electrodes). This dual asymmetry approach allows the system to maintain functional versatility while correcting the non-linear field characteristics introduced by the ejection slots.
3Ease of operation
If non-matching RF signal voltage levels are applied to X and Y electrodes, then centerline potential is balanced, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by adjusting the RF signal voltage levels applied to the X and Y electrodes. The system uses a signal generator capable of outputting RF signals with different amplitude levels to the X and Y electrode pairs. This parameter adjustment simplifies the overall device operation by automatically balancing the centerline potential through controlled voltage differentiation, without requiring complex mechanical adjustments or additional balancing components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration minimizes non-linear field components, resulting in improved linear field characteristics and balanced centerline potentials, enhancing ion trap performance by maintaining efficient ion injection and reducing mass bias.
Implementation Method 1
a first radio-frequency (RF) signal is applied to the Y electrodes which effects trapping of injected ions within the ion trap. Similarly, a second RF signal is applied to the X electrodes which effects trapping of injected ions within the ion trap
Implementation Method 2
Ions from a test sample trapped within the ion trap may be ejected or 'scanned out' in a mass-selective manner through one or more ejection slots in the ion trap
Data Source
AI summary
A system and method are disclosed for effectively compensating for an unbalanced or non-zero centerline radio-frequency potential in a quadrupolar ion trap, the unbalanced centerline potential created by a compensation feature that minimizes non-linear field components created by one or more ejection slots in the ion trap. The ion trap includes a centerline that passes longitudinally through a trapping volume inside of the ion trap, a pair of Y electrodes with inner Y electrode surfaces that are approximately parallel to the centerline, and a pair of X electrodes with inner X electrode surfaces that are approximately parallel to the centerline. The X electrodes have ejection slots through which trapped ions are ejected from the ion trap. A Y signal with a Y signal amplitude is coupled to both of the Y electrodes. An X signal with an X signal amplitude is coupled to both of the X electrodes. The X signal amplitude is selected to be greater than the Y signal amplitude to thereby create a balanced centerline potential at the centerline of the ion trap device.