Electron Microscope NEG Placement on Extraction Electrode
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Solution Overview
Problem
Existing electron microscopes with ion pumps and non-evaporable getters (NEGs) require dedicated heaters to activate the NEG, leading to gas emission that can adversely affect the electron source and necessitate frequent maintenance and replacement.
Innovation Solution
An electron microscope design where a NEG is integrated on the extraction electrode, utilizing the inner heater of the electron gun to activate the NEG at a lower temperature, reducing gas emission and extending the emission current stability without a separate heater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated heater is provided to activate the NEG, then the NEG can be activated and pump residual gas molecules, but the device complexity increases and gas molecules are emitted that may adversely affect the electron source
Solution Approach 1:
The extraction electrode heater serves dual functions: heating the extraction electrode for electron emission and activating the NEG for residual gas pumping. This eliminates the need for a separate dedicated heater, reducing device complexity while maintaining effective NEG activation and pumping capability.
Solution Approach 2:
The NEG is integrated with the extraction electrode structure, combining the electron extraction function and the residual gas pumping function into a single component assembly. This merging reduces the number of separate components and simplifies the overall device structure.
2Reliability
If a dedicated heater is wound around the NEG, then the NEG can be activated, but the structure becomes more complex and requires additional space around the electron source
Solution Approach 1:
The extraction electrode heater performs both extraction electrode heating and NEG activation functions, eliminating the need for a separate coil around the NEG and simplifying the heater arrangement.
Solution Approach 2:
The need for a separate heater structure around the NEG is extracted/removed from the system by utilizing the existing extraction electrode heater, thereby simplifying the overall structure and reducing spatial requirements.
3Reliability
If the NEG is activated by heating to high temperature, then gas molecules are emitted and absorbed, but this may adversely affect the electron source performance
Solution Approach 1:
The NEG is positioned on the extraction electrode where it can effectively pump residual gas molecules in the critical region near the electron source without requiring high-temperature activation that would emit harmful gas. The local placement enables effective pumping at lower temperatures.
Solution Approach 2:
The extraction electrode acts as an intermediary structure that hosts the NEG in a strategic position, enabling the NEG to pump residual gas molecules before they reach the electron source, thereby protecting the electron source from contamination while activating the NEG.
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 allows for a stable emission current over a longer period, reducing maintenance and replacement needs, and maintaining a clean electron source surface, thereby enhancing observation image stability and extending the electron source's lifespan.
Implementation Method 1
The NEG is a porous metal rod and employs chemisorption on metal atoms of a surface as a pumping principle
Implementation Method 2
The activated NEG sorbs and pumps residual gas molecules such as hydrogen, nitrogen, carbon monoxide
Data Source
AI summary
The present invention is to provide an electron microscope capable of being activated to an appropriate temperature by disposing an NEG at an extraction electrode around an electron source. The present invention is an electron microscope provided with an electron gun, in which the electron gun includes an electron source, an extraction electrode, and an accelerating tube, the accelerating tube is connected to the extraction electrode at a connection portion, the extraction electrode includes a first heater and a first NEG, and the first heater and the first NEG are spaced apart in an axial direction of an electron beam emitted from the electron source.