Ionization Gauge Cold Emitter Microchannel Plate
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Solution Overview
Problem
Bayard-Alpert ionization gauges face issues with hot cathode filament degradation due to chemical reactions with gaseous environments, leading to reduced operational lifetime, especially when exposed to high pressures or water vapor, necessitating a reliable cold electron emitter that does not alter the gas composition or degrade the gauge.
Innovation Solution
A cold electron emitter ionization gauge utilizing a microchannel plate with an electron generating portion for seed electron production and an electron multiplier portion to multiply electrons, which can be treated for spontaneous emission, eliminating the need for a hot cathode filament and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hot cathode filament is used to generate electrons, then electron emission is achieved, but the filament degrades due to chemical reactions with gaseous environments, reducing operational lifetime
Solution Approach 1:
The patent removes the hot cathode filament (the harmful component) from the ionization gauge system and replaces it with a cold cathode electron emission mechanism using spindt emitters. This extraction eliminates the chemical reactions between heated filament materials and gaseous substances that cause degradation, while maintaining electron generation capability through field emission from cold cathode tips.
Solution Approach 2:
The patent replaces the thermal-mechanical electron emission system (hot cathode filament requiring high temperature) with an electrostatic field emission system (cold cathode spindt emitters). This substitution eliminates the need for thermal energy input and the associated chemical reactions that occur at elevated temperatures, thereby improving reliability without mechanical degradation.
2Object-affected harmful factors
If a cold cathode with tipped micro-points is used for electron emission, then chemical reactions are avoided, but the micro-points erode from ion bombardment, degrading emissivity and causing gauge failure
Solution Approach 1:
The patent applies a protective coating or treatment to the spindt emitter micro-points before operation to cushion them against ion bombardment erosion. This pre-applied protection layer absorbs or redistributes the impact energy from ion strikes, preventing direct damage to the underlying emitter material and maintaining emissivity over extended operational periods.
Solution Approach 2:
The patent uses composite material structures for the cold cathode spindt emitters, combining multiple materials with complementary properties. The composite structure provides both high field emission capability and resistance to ion bombardment erosion, addressing both the need for electron emission and protection against mechanical degradation from ion impacts.
3Use of energy by moving object
If a hot cathode filament is used, then electron generation is achieved, but the oxide coating on the filament degrades, reducing electron emission properties
Solution Approach 1:
The patent replaces the thermal field emission mechanism (requiring heated oxide-coated filament) with a cold field emission mechanism using spindt emitters. This substitution eliminates the thermal degradation of oxide coatings while maintaining electron generation capability through quantum tunneling field emission from sharp cold cathode tips, thereby stabilizing emission characteristics over time.
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 provides a long-lasting, reliable pressure measurement system that functions without degrading the gauge or altering the gas composition, offering improved operational stability and resistance to environmental degradation.
Implementation Method 1
a microchannel plate with an electron generating portion for seed electron production and an electron multiplier portion to multiply electrons
Implementation Method 2
The microchannel plate can be treated to cause a spontaneous emission of seed electrons
Implementation Method 3
In their travel, the electrons impact molecules and atoms of gas, constituting the atmosphere whose pressure is to be measured, and create ions
Data Source
AI summary
An ionization gauge includes an electron generator array that includes a microchannel plate that includes an electron generating portion of the microchannel plate comprising a source for generating seed electrons and an electron multiplier portion of the microchannel plate, responsive to the seed electrons generated by the electron generating portion, that multiplies the electrons. The ionization gauge includes an ionization volume in which the electrons impact a gaseous species, and a collector electrode for collecting ions formed by the impact between the electrons and gas species. The collector electrode can be surrounded by the anode, or the ionization gauge can be formed with multiple collector electrodes. The source of electrons can provide for a spontaneous emission of electrons, where the electrons are multiplied in a cascade.