Electron Gun Electrode Configuration for Brightness and Vacuum
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Solution Overview
Problem
Existing electron beam devices require stringent ultra-high vacuum conditions for operation, which are costly and time-consuming to maintain, and suffer from low brightness due to high energy spread and chromatic aberration, limiting their performance in achieving high-resolution imaging.
Innovation Solution
An electron gun design featuring a thermionic source with a unique electrode configuration that adjusts voltages to prevent electron crossover, allowing operation at lower vacuum pressures (10^-5 to 10^-7 mbar) and enhancing electric field strength near the emission surface, reducing space charge and chromatic aberration, thereby increasing brightness and emission current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If field-emission sources are used to achieve high brightness, then electron beam brightness is improved, but vacuum conditions must be maintained at ultra-high levels (lower than 10^-9 mbar) which increases complexity and cost
Solution Approach 1:
The patent changes the operating parameters of the electron source by using a thermionic emission mechanism instead of field emission, allowing operation at lower vacuum levels (10^-5 to 10^-7 mbar) while maintaining acceptable brightness through thermal excitation of electrons from a heated cathode
2Ease of operation
If thermionic sources are used to simplify vacuum requirements, then ease of operation is improved, but brightness is reduced due to high energy spread and chromatic aberration
Solution Approach 1:
The patent introduces dynamic voltage control through a suppressor electrode that can be adjusted during operation to optimize the electric field distribution, dynamically compensating for chromatic aberration and energy spread effects to maintain high brightness while using a thermionic source
Solution Approach 2:
The patent modifies the energy distribution of emitted electrons by applying specific voltage potentials to the suppressor electrode, changing the effective energy spread parameter to reduce chromatic aberration and improve beam brightness
3Use of energy by moving object
If high voltage is applied to accelerate electrons, then electron beam energy is improved, but crossover of electrons occurs in the acceleration area which reduces brightness
Solution Approach 1:
The suppressor electrode acts as an intermediary element between the cathode and anode, creating an intermediate electric field zone that guides electron acceleration while preventing crossover, thereby maintaining both high energy and high brightness
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 brightness and reduced chromatic aberration, enabling high-resolution imaging with easier vacuum maintenance and increased emission current, facilitating efficient operation in scanning and transmission electron microscopes.
Implementation Method 1
a thermionic source which emits electrons when heated
Implementation Method 2
enhancing electric field strength near the emission surface
Implementation Method 3
a third electrode configured to accelerate electrons emitted from the electron source to a final energy
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The invention relates to an electron gun (101, 201) used in a particle beam device, for example in an electron microscope. The electron gun (101, 201) has a relatively good brightness and may be operated under vacuum conditions which can be easily achieved (i.e., for example, at a residual pressure of about 10 -6 or 10 -7 mbar). The electron gun (101, 201) comprises an electron source (300) having an electron emission surface (306). Furthermore, the electron gun (101, 201) comprises a first electrode (301) configured to control a path of electrons emitted from the electron emission surface (306), a second electrode (304) which is configured to suppress emissions of electrons from a side surface of the electron source (300) and a third electrode (305) configured to accelerate electrons emitted from the electron source (300) to a final energy. A first voltage, a second voltage and a third voltage are adjusted to avoid any crossover of electrons emitted from the electron emission surface (306).