Thermionic Emitter Shielding for Insulator Deposition Control
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Solution Overview
Problem
The reliability of emission current is impaired due to evaporated matter from the heater and electron source depositing on insulator surfaces, leading to deteriorated insulation and unintended current flow under high-temperature conditions.
Innovation Solution
An emitter design featuring a shielding member to prevent continuous conductive layer formation between conductive terminals and Wehnelt electrode, combined with an intermediate member of lower thermal conductivity to manage heat distribution and maintain insulation, ensuring the electron source is efficiently heated without material deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater and electron source are heated to high temperatures (1600-1900K) to generate emission current, then the electron emission performance is improved, but evaporated matter deposits on the insulator surface causing deterioration of insulation properties and unintended current flow
Solution Approach 1:
A shielding member made of insulating material is introduced as an intermediary component between the heater/electron source and the insulator surface. This shielding member intercepts evaporated matter before it reaches the insulator surface, preventing deposition and insulation deterioration while allowing the heater to operate at high temperatures for reliable electron emission
Solution Approach 2:
The insulator surface is segmented into different functional zones by the shielding member. The shielding member creates a protected zone on the insulator surface that is shielded from evaporated matter, while other areas can serve different functions. This segmentation allows the insulator to maintain its insulation properties in critical areas
2Reliability
If a shielding member is added to prevent evaporated matter deposition on the insulator, then insulation reliability is improved, but device complexity increases
Solution Approach 1:
The shielding member is designed to serve multiple functions simultaneously: it shields the insulator surface from evaporated matter, provides structural support for positioning the heater and electron source, and can be integrated with existing emitter components. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity
3Reliability
If an intermediate member with lower thermal conductivity is used between the electron source and heater, then material evaporation is suppressed, but heat transfer efficiency to the electron source decreases
Solution Approach 1:
The intermediate member is designed with specific thermal conductivity parameters that balance two opposing requirements: low enough to reduce heat transfer to the heater (suppressing evaporation) but high enough to efficiently heat the electron source. By optimizing this thermal conductivity parameter, the system achieves both reduced material evaporation and adequate electron source heating
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 emitter maintains reliable emission current for a prolonged period by suppressing material deposition and maintaining high insulation levels, thus enhancing the durability of electron-emitting devices.
Implementation Method 1
a heater disposed between tips of the pair of conductive terminals and generating heat when energized
Implementation Method 2
an electron source heated by the heater and made of a first material emitting electrons
Implementation Method 3
Under high-temperature conditions, the materials that make up the heater and/or electron source may evaporate, thereby producing evaporated matter
Implementation Method 4
When this evaporated matter cools and solidifies, for example, on the surface of an insulator
Data Source
AI summary
An emitter includes: an insulator; a pair of conductive terminals attached to the insulator and spaced apart from each other; a heater disposed between tips of the pair of conductive terminals and generating heat when energized; an electron source heated by the heater and made of a first material emitting electrons; a Wehnelt electrode having an inner surface forming an internal space along with a surface of the insulator, and applying a bias voltage across the Wehnelt electrode and the electron source; and a shielding member covering a part of the surface of the insulator in the internal space.