Ion Mirror Fringe Field Correction for Higher ToF Resolution
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Solution Overview
Problem
Existing ion mirrors in time of flight mass spectrometry face challenges due to fringe field perturbations, which require a large number of electrodes with precise voltage control, leading to inaccuracies and drift over time, limiting the usable length and resolution of the ion mirror.
Innovation Solution
Incorporating a Fringe Field Correcting (FFC) assembly at the ends of the ion mirror, which suppresses fringe field perturbations using a simplified voltage distribution derived from existing mirror electrode voltages, reducing the need for additional resistor chains and allowing for increased usable length and resolution without increasing the overall size of the ion mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional fringe field correctors are used to minimize fringe field perturbation, then the electrostatic field planar symmetry is improved, but the device complexity increases due to requiring a large number of electrodes with precise voltage control via resistor chains
Solution Approach 1:
The patent extracts only the essential function of fringe field correction by using a simplified electrode structure that provides the necessary field symmetry without requiring complex resistor chains and multiple precisely-controlled electrodes. The invention takes out the problematic voltage division circuitry while retaining the core correction capability through a more straightforward electrode configuration.
Solution Approach 2:
The ion mirror electrodes themselves are configured to provide fringe field correction as an inherent property of their geometry and voltage distribution, rather than requiring separate dedicated correcting electrodes with independent voltage control. The mirror electrodes serve both their primary reflection function and the fringe field correction function simultaneously.
2Measurement precision
If the length of ion mirrors is increased to achieve higher resolution, then the maximum resolution is improved, but the usable region is reduced at the ends due to electrostatic field deviation from planar symmetry
Solution Approach 1:
The patent applies local quality by modifying the electrode geometry and voltage distribution specifically at the end regions of the ion mirror where fringe fields occur, while maintaining the standard configuration in the central usable region. This localized adjustment preserves planar symmetry at the ends without compromising the overall mirror performance or central region usability.
3Measurement precision
If resistor chains are used to provide precise voltages to correcting electrodes, then the fringe field correction precision is improved, but the reliability decreases due to tolerance accumulation and resistance drift over time
Solution Approach 1:
The patent removes the resistor chain voltage division circuitry entirely, replacing it with a configuration that derives correcting electrode voltages directly from the mirror electrode voltages through simple electrical connection. This extraction of the problematic intermediate voltage division stage eliminates tolerance accumulation and drift issues while maintaining sufficient correction precision.
Solution Approach 2:
The patent merges the voltage supply for correcting electrodes with the existing mirror electrode voltage sources, so that both sets of electrodes are controlled from the same voltage references. This combining eliminates the need for separate precision voltage division circuits and their associated reliability problems.
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
The FFC assembly enhances the planar symmetry of the electrostatic field, increasing the usable length of the ion mirror, allowing for more reflections and a greater maximum flight length, thereby improving the resolution of the time of flight mass spectrometer while reducing space, weight, and cost.
Implementation Method 1
Each electrode of the plurality of electrodes is configured to receive a respective FFC voltage. The FFC assembly is configured to suppress a fringe perturbation of the electrostatic field of the ion mirror when biased with the FFC voltages.
Data Source
AI summary
An ion mirror for a time of flight mass spectrometer (ToF) is provided. The ion mirror is elongated from a first end to a second end along a drift direction (z) and is configured to reflect ions in a reflection direction (y) orthogonal to the drift direction. The ion mirror comprises a plurality of elongate mirror electrodes and at least one Fringe Field Correcting (FFC) assembly. Each of the elongate mirror electrodes extends in the drift direction. Each of the plurality of elongate mirror electrodes is configured to receive a respective mirror electrode voltage in order to provide an electrostatic field of the ion mirror. The at least oneFFC assembly is provided at the first and/or second end of the ion mirror. The FFC assembly comprises a plurality of electrodes, the plurality of electrodes extending in a plane orthogonal to the drift direction, each electrode configured to receive a respective FFC voltage. The FFC assembly is configured to suppress a fringe perturbation of the electrostatic field of the ion mirror when biased with the FFC voltages.