Virtual-Source Electron Gun for Narrow Energy Spread
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Solution Overview
Problem
Conventional electron guns face challenges in achieving high angular current density, narrow energy distribution, and stable electron emission characteristics, particularly in high-resolution imaging applications, due to large source size and wide energy distribution caused by crossover point formation, which limits their performance in ultra-high vacuum environments.
Innovation Solution
An electron gun using a virtual source method is developed, featuring a lanthanum hexaboride (LaB6) or cerium hexaboride (CeB6) emitter with a suppressor electrode and extraction electrode, where the suppressor electrode is positioned behind the emitter tip, and the extraction electrode is applied with a voltage to induce field emission, forming a virtual source inside the emitter, allowing for improved electron beam emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crossover point is formed by a Wehnelt electrode in front of a thermal electron source, then electron beam emission is achieved, but the source size becomes large (tens of micrometers) and energy distribution becomes wide, making high-resolution imaging difficult
Solution Approach 1:
A suppressor electrode is introduced as an intermediary component between the thermal electron source and the extraction electrode. This suppressor electrode creates a virtual source configuration that mediates the electron emission process, allowing the physical source to remain small while achieving stable beam extraction without forming a large crossover point
Solution Approach 2:
The patent changes the electrical parameters by applying specific voltages to the suppressor and extraction electrodes. By controlling the voltage distribution in the electron emission region, a virtual source is formed that has different effective parameters than the physical thermal source, achieving small effective source size with narrow energy distribution
2Reliability
If a crossover point is formed by a Wehnelt electrode, then electron beam emission is achieved, but energy distribution becomes wide due to electron interaction, increasing chromatic aberration in electromagnetic lens
Solution Approach 1:
The suppressor electrode acts as a mediator that controls electron trajectories before they interact. By positioning and voltage-controlling this intermediary electrode, electrons are guided in a manner that reduces mutual interactions, resulting in narrower energy distribution and reduced chromatic aberration
Solution Approach 2:
The suppressor electrode performs preliminary action on the electrons by establishing an electric field configuration before the electrons are fully extracted. This preliminary field control prevents excessive electron interaction and energy spreading, achieving narrow energy distribution from the outset
3Ease of operation
If a physical source size is large (1 eV) as in thermionic emission type electron gun, then operation in high vacuum is easy, but high-resolution imaging cannot be achieved
Solution Approach 1:
The suppressor electrode serves as a mediator that decouples the relationship between physical source size and effective source size. The physical thermal source can remain relatively large for ease of operation in high vacuum, while the suppressor electrode creates a virtual source configuration that presents a small effective source size for high-resolution imaging
Solution Approach 2:
The patent changes the effective parameters of the source by introducing controlled electric fields through the suppressor and extraction electrodes. This transforms the apparent source characteristics, making the effective source size and energy distribution suitable for high-resolution work while maintaining the operational advantages of thermal emission sources
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 electron gun achieves high angular current density, narrow energy distribution, and stable electron emission, enabling high-resolution imaging with improved signal-to-noise ratio and reduced maintenance costs, while operating in a low-vacuum environment and at lower tip heating temperatures.
Implementation Method 1
the emitter has a virtual source formed therein and emits the electron beam to the outside; The emitter may be formed of lanthanum hexaboride (LaB6) or cerium hexaboride (CeB6)
Implementation Method 2
the extraction electrode is applied with a voltage to induce field emission, forming a virtual source inside the emitter
Data Source
AI summary
Provided is an electron gun using a virtual source method that may have a high angular current density, a narrow energy distribution, and stable electron emission characteristics by forming a virtual source inside a thermal electron source (LaB6, CeB6)-based emitter emitting an electron beam.