Gridless Ion Mirror Field Segmentation for High Energy Acceptance
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Solution Overview
Problem
Existing gridless ion mirrors in time-of-flight mass spectrometers suffer from limited ion optical quality, particularly in terms of mass resolving power and energy acceptance, due to uniform electric fields that do not adequately compensate for high-order aberrations and spatial isochronicity, especially when used in multi-reflecting TOF and electrostatic traps.
Innovation Solution
The design of ion mirrors with segmented linear potential distributions and controlled non-uniformity achieved through resistive chains and thin electrodes on printed circuit boards, allowing for controlled field penetration and curvature at the ion turning point, enhancing ion optical quality by improving energy and spatial acceptance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform electric fields are used in gridless ion mirrors, then the structure is simple and easy to manufacture, but the ion optical quality is limited with poor mass resolving power and energy acceptance
Solution Approach 1:
The ion mirror is divided into multiple axial segments (first axial segment, second axial segment, etc.) with different field strengths. Each segment is defined by inter-segment electrodes that can be independently controlled, allowing the creation of non-uniform electric field distributions that compensate for high-order aberrations while maintaining reasonable structural complexity through modular design
Solution Approach 2:
Different axial segments are assigned different electric field strengths (E1, E2, E3) optimized for specific local functions. The first axial segment has field strength E1, the second has E2, and the third has E3, where each field strength is tailored to compensate for aberrations in that specific region, improving overall ion optical quality without requiring complete redesign of the entire mirror structure
2Device complexity
If uniform electric fields are used in ion mirrors, then the device complexity is low, but energy acceptance and spatial isochronicity are insufficient
Solution Approach 1:
The electric field distribution is made dynamic and adjustable through independent voltage control of inter-segment electrodes. The voltage supplies can be adjusted to optimize field penetration and curvature at the ion turning point for different ion energies, enabling the mirror to adapt to a wide energy spread (20%) while maintaining high resolving power
Solution Approach 2:
The electric field parameters (strength, penetration depth, curvature) are optimized by adjusting the voltage applied to inter-segment electrodes. The field strength ratios (E2/E1, E3/E2) and penetration depths (X2, X3) are tuned to achieve fifth-order energy isochronicity and full third-order spatial isochronicity, significantly improving energy acceptance without excessive device complexity
3Length of moving object
If multi-reflecting TOF is implemented to improve resolution, then the ion path length increases substantially, but ion losses and scattering increase at multiple grid passages
Solution Approach 1:
The grids are completely removed from the ion mirror structure, eliminating the source of ion losses and scattering. Instead of using grids to define the electric fields, the invention uses open electrode structures with resistive chains that generate the required field distributions without physical barriers in the ion path, enabling multi-reflecting TOF with L=20-50m while minimizing ion losses
4Strength
If thick electrodes are used to generate desired field distributions, then the field penetration is limited, but the manufacturing is more complex and ion optical quality is compromised
Solution Approach 1:
Thin electrodes are used instead of thick electrodes, allowing better field penetration into the drift space while maintaining the ability to generate desired field distributions. The thin electrodes are supported by resistive chains that provide the necessary voltage gradients, achieving a balance between field generation capability, field penetration, and structural simplicity
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 approach achieves unprecedented mass resolving powers above 100,000 for a wide energy spread of 20%, significantly improving the turn-around time of ion packets and resolving power in multi-reflecting TOF mass spectrometers and electrostatic traps.
Implementation Method 1
voltage supplies for applying different voltages to different electrodes of the ion mirror for generating electric fields for performing said reflecting of the ions
Implementation Method 2
resistive chains and thin electrodes on printed circuit boards, allowing for controlled field penetration and curvature at the ion turning point
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An ion mirror 41constructed of thin electrodes that are interconnected by resistive dividers45 with potentials U1-U5 applied to knot electrodes to form segments 41-43 of linear potential distribution between the "knot" electrodes, yet without separating those field regions by meshes. Weak and controlled penetration of electric fields provide for a fine control over the field non linearity and over the equipotential line curvature, thus allowing to reach unprecedented level of ion optical quality: more than twice larger energy acceptance compared to thick electrode mirrors, up to sixth order time per energy focusing, ion spatial focusing and wide spatial acceptance. Novel mirrors can be formed very slim to arrange them into stacks for ion transverse displacement between ion reflections or for multiplexed mirror stacks. Printed circuit boards (PCB) are best suited for making novel ion mirrors, while novel ion mirrors are designed to suit PCB requirements.