Electron Gun Cathode Through Hole No-Emitting Layer
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Solution Overview
Problem
Existing electron guns face issues with electron emission from the inner surface of through holes in the cathode, leading to disturbed electron beam formation and the production of dark current due to secondary electrons and ions, which can cause damage and overheating.
Innovation Solution
The electron gun incorporates a no-emitting layer at the opening edge or inner surface of the through hole, either as a metal layer, a porous metal base body, or a ceramic-impregnated layer, or chamfers the edge to prevent electron emission, thereby eliminating dark current and maintaining electron beam integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through hole is formed in the cathode to prevent back bombardment damage, then the cathode is protected from overheating, but electron emission from the through hole causes disturbed electron beam formation and dark current production
Solution Approach 1:
The invention applies a no-emission coating specifically to the inner surface of the through hole, creating a localized region with different emission properties. This allows the through hole to maintain its protective function while preventing unwanted electron emission from its inner surface, thus resolving the contradiction between cathode protection and dark current prevention.
Solution Approach 2:
The no-emission coating acts as an intermediary layer between the through hole structure and the electron emission process. This coating material prevents direct electron emission from the through hole inner surface while allowing the through hole to continue providing back bombardment protection, thereby eliminating dark current without sacrificing reliability.
2Productivity
If emitter material is deposited on the cathode surface, then electron emission is enhanced, but material scattering and evaporation can attach in the through hole causing unwanted electron emission
Solution Approach 1:
The no-emission coating is applied to the through hole inner surface before or during the emitter material deposition process. This preliminary protective layer prevents emitter material from accumulating in the through hole, thereby eliminating the source of unwanted electron emission while allowing normal emitter deposition on the cathode emitting surface to proceed.
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 solution effectively suppresses electron emission from the through hole, preventing disturbance of electron beam formation and reducing the risk of damage to the cathode and anode, while maintaining efficient electron flow and beam focus.
Implementation Method 1
a heater (105) to heat a cathode (102)
Implementation Method 2
an electron gun (101) to emit thermions by using a heater (105) to heat a cathode (102) in which a thermionic emission substance is splayed onto, coated onto, or impregnated into a metal base body
Implementation Method 3
it is used by applying, to an anode (103) and a wehnelt (104), a positive electric potential relative to the cathode (102)
Implementation Method 4
a control can be performed in which the flow of electrons is cutoff with an electric field by applying, to the grid (106), a negative electric potential relative to the cathode (102)
Data Source
AI summary
An electron gun comprising a cathode having an electron emitting surface and whose planar shape is circular, a heater to increase the temperature of the cathode, and an anode to apply a positive electric potential relative to the cathode to extract electrons in a predetermined direction is provided. The cathode comprises a through hole at a central portion thereof along a central axis of the cathode, and either the cathode comprises a no-emitting layer at at least one of an opening edge on the electron emitting surface side of the through hole and an inner surface of the through hole, or the opening edge on the electron emitting surface side of the through hole is a chamfered C surface or a chamfered R surface.