LaB6 Field Emitter Assembly With Tantalum Adapter Welding
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Solution Overview
Problem
The material incompatibility between LaB6 and conventional emitter support materials leads to erosion and contamination issues in cold field emission electron sources, making it difficult to operate in ultra-high vacuum conditions.
Innovation Solution
An adapter made of tantalum is used to couple the LaB6 electrode to a tungsten filament, forming fusion zones through spot welding or laser welding without filler material, creating a mechanically stable emitter assembly compatible with ultra-high vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If LaB6 electrode is directly attached to conventional emitter support materials, then mechanical stability is improved, but erosion and contamination occur due to material incompatibility
Solution Approach 1:
A tantalum adapter is introduced as an intermediary component between the LaB6 electrode and the tungsten filament. The adapter forms fusion zones with both materials through welding, creating a stable mechanical connection while preventing direct contact between incompatible materials, thereby eliminating erosion and contamination issues.
2Reliability
If adapter is welded to electrode and filament, then mechanical stability and vacuum compatibility are improved, but manufacturing complexity increases
Solution Approach 1:
The adapter is designed to be welded to both the electrode and filament in a single assembly operation, merging multiple functions (mechanical support, electrical connection, vacuum compatibility) into one integrated component that simplifies the overall manufacturing process.
3Productivity
If high temperature heating is applied for thermal flashing, then cleaning effectiveness is improved, but material erosion and joint degradation worsen
Solution Approach 1:
The emitter assembly uses a composite structure with tantalum adapter material that has superior high-temperature stability compared to conventional materials. This allows the assembly to withstand repeated thermal flashing cycles at high temperatures without experiencing significant material erosion or joint degradation, enabling effective cleaning while maintaining structural integrity.
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 mechanically stable and vacuum-compatible emitter assembly that tolerates high temperatures, reducing erosion and contamination, ensuring long-term stable operation of LaB6 cold field emission sources.
Implementation Method 1
Respective fusion zones bond the adapter to the electrode and to the filament. Illustratively, a LaB6 electrode can be attached to a tungsten filament through a tantalum adapter, however other materials and combinations can be used. Fusion zones can be formed by spot welding or laser welding without filler material
Implementation Method 2
In other examples, welding can be used to form a fusion zone between adapter and electrode, and another technique can be used to assemble the adapter and filament. Illustratively, a tantalum adapter can be formed by deposition onto the filament.
Data Source
Figure 1A~2
Figure 3A~3B
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AI summary
Apparatus and methods are disclosed for a mechanically stable, long-life, cold field emitter assembly which is compatible with ultra-high vacuum and occasional high-temperature flashing. A metal adapter is welded between a hexaboride electrode and a metal filament. Some embodiments use a tungsten filament, a tantalum adapter, and a LaB6 microrod electrode with a nanorod emitter tip. Other material combinations are disclosed, as also usage in electron sources for electron microscopes. In variations, the adapter is deposited onto the filament and the electrode then welded to the adapter.