Spherical Sector Extraction System for Mass Spectrometers
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Solution Overview
Problem
Existing secondary ion mass spectrometry (SIMS) systems face challenges in efficiently extracting charged secondary particles while minimizing the deleterious effects on the primary ion beam, leading to aberrations and reduced lateral resolution due to the extraction field, particularly when the primary and secondary ions are not of opposite polarity.
Innovation Solution
A charged particle beam deflecting system comprising inner and outer spherical sectors with a deflecting gap, an intermediate electrode, and side plates, where the spherical sectors are biased to deflect the charged particle beam by a given angle, and the intermediate electrode is biased between the exit wall potential and the spherical sector potentials to reduce energy and correct focusing effects, ensuring a parallel beam exit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an extraction field is applied to collect secondary ions, then secondary ion collection efficiency is improved, but primary ion beam aberrations increase and lateral resolution deteriorates
Solution Approach 1:
The extraction system is divided into multiple independent electrode regions (first extraction electrode, second extraction electrode, third extraction electrode) with distinct functional zones. Each electrode can be independently controlled to manage extraction fields separately, allowing optimization of secondary ion collection while minimizing interference with the primary ion beam path.
Solution Approach 2:
A guard electrode is introduced as an intermediary element between the extraction electrodes and the primary ion beam path. This guard electrode creates a potential barrier that prevents extraction fields from deflecting primary ions, thereby maintaining beam integrity while allowing secondary ion extraction to proceed efficiently.
2Manufacturing precision
If the primary and secondary ions are made coaxial to minimize aberrations, then lateral resolution is improved, but the system is limited to opposite polarity ions only
Solution Approach 1:
The system separates the extraction function from the beam axis by using electrodes positioned in regions that do not interfere with the primary ion path. The extraction fields are applied in dimensions perpendicular to or separated from the main beam axis, allowing non-opposite polarity ions to be extracted without compromising lateral resolution or requiring coaxial alignment.
3Productivity
If extraction fields are strengthened to enhance secondary ion collection, then collection efficiency is improved, but primary beam deflection increases
Solution Approach 1:
The harmful effect of beam deflection is extracted and isolated by positioning extraction electrodes away from the primary beam path. The extraction fields are confined to specific regions that do not overlap with the primary ion trajectory, allowing strong extraction fields to be applied without causing beam deflection.
Solution Approach 2:
The guard electrode serves as a mediator that shields the primary ion beam from extraction fields. By maintaining a potential barrier on the guard electrode, strong extraction fields can be applied to collect secondary ions while the guard electrode prevents these fields from deflecting the primary beam.
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 reduces aberrations and deflection of the primary beam, allowing for high lateral resolution analysis and efficient transport of secondary particles, maintaining beam quality and reducing the focusing effect, thus enhancing the extraction system's efficiency and compatibility with existing instrumentation.
Implementation Method 1
the spherical sectors being biased at deflecting potentials in order to deflect the charged particle beam entering the deflecting gap by a given angle
Implementation Method 2
the intermediate electrode is biased at an intermediate potential between the exit wall potential and the average potential of the spherical sectors
Data Source
AI summary
The invention is directed to mass spectrometer comprising an extraction system for secondary ions. The system comprises: an inner spherical deflecting sector; an outer spherical deflecting sector; a deflecting gap formed between the sectors; a housing in which the sectors are arranged. The deflecting sectors (42; 44) are biased at retarding gap (46). The system further comprises an exit disc electrode with an exit through hole centered about the exit axis, the intermediate electrode being biased at an intermediate voltage between the voltage of the housing and the average voltage of the sectors. The trajectories of the secondary ions become more parallel to the exit axis and become closer to the axis.