Layered Insulating Substrate for Electron Tube Dark Current Control
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Solution Overview
Problem
Insulating substrates in electron tubes experience electron incidence leading to light emission, which increases dark current, necessitating a technique to suppress both charging and light emission.
Innovation Solution
The electron tube incorporates a polycrystalline base layer with an amorphous intermediate layer and a carbon-containing surface layer to manage electron incidence and charging, with the intermediate layer being thicker than the surface layer to enhance suppression efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating substrate with high electrical insulation property is used, then charging is suppressed, but light emission occurs due to electron incidence
Solution Approach 1:
The insulating substrate is segmented into multiple functional layers: a base layer for mechanical strength, an intermediate layer for electron incidence suppression, and a surface layer for charging suppression. This segmentation allows each layer to specialize in one function, resolving the contradiction between insulation and light emission suppression.
Solution Approach 2:
Different layers are assigned different material properties tailored to their specific functions. The intermediate layer uses amorphous material with specific electron interaction properties, while the surface layer uses carbon-containing material with low electric resistance. This local differentiation of material qualities enables simultaneous achievement of electron suppression and charging prevention.
2Reliability
If a surface layer with low electric resistance is added to suppress charging, then charging is reduced, but the layer may increase light emission
Solution Approach 1:
The intermediate layer acts as an intermediary between the base layer and the surface layer. It prevents direct electron incidence to the base layer while allowing the surface layer to function for charging suppression. This intermediary structure resolves the potential conflict between low-resistance surface layer and light emission suppression.
Solution Approach 2:
The insulating substrate employs a composite structure combining different materials: polycrystalline base material, amorphous intermediate material, and carbon-containing surface material. This composite approach integrates the beneficial properties of each material to simultaneously achieve charging suppression and light emission reduction without mutual interference.
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 configuration effectively suppresses both charging and light emission of the insulating substrate, ensuring reliable operation by minimizing electron-induced light emission and surface charging.
Implementation Method 1
a photoelectric surface that converts incident light into photoelectrons
Implementation Method 2
a multiplier that multiplies the photoelectrons by secondary electron emission based on the incident photoelectrons
Data Source
AI summary
An electron tube includes: a photoelectric surface converting incident light into photoelectrons; a plurality of dynodes and an anode; an insulating substrate holding the dynodes and the anode in a state where the dynodes are electrically insulated from each other, and the dynode and the anode are electrically insulated from each other; and a housing accommodating the dynodes, the anode, and the insulating substrate, wherein the insulating substrate includes: a base layer made of a polycrystalline material and having an electrical insulation property; an intermediate layer made of an amorphous material and having an electrical insulation property; and a surface layer made of a material containing carbon and being smaller in electric resistance than the intermediate layer.