LaB6 Emitter Adapter Assembly for Ultra-High Vacuum Stability
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Solution Overview
Problem
Existing cold field emission electron sources using lanthanum hexaboride (LaB6) face material incompatibility issues with emitter support materials, leading to erosion and vacuum contamination, which hinder stable operation in ultra-high vacuum conditions.
Innovation Solution
An adapter, typically made of tantalum, is used to couple the LaB6 electrode with a tungsten filament through fusion zones formed by spot welding or laser welding, eliminating the need for filler materials and ensuring mechanical stability and compatibility with ultra-high vacuum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite paste is used to bond LaB6 to support, then material incompatibility is overcome, but trapped gas reservoir forms making ultra-high vacuum operation difficult
Solution Approach 1:
The invention extracts and eliminates the graphite paste bonding layer from the emitter assembly. By directly bonding LaB6 to the tungsten filament without intermediary graphite paste, the source of trapped gas reservoirs and vacuum contamination is removed, enabling stable ultra-high vacuum operation
Solution Approach 2:
The invention introduces a specialized bonding interface that directly couples LaB6 to tungsten filament through compatible material layers or surface treatments. This intermediary bonding mechanism eliminates the need for graphite paste while maintaining material compatibility and preventing erosion
2Reliability
If graphite paste is used to bond LaB6 to support, then material incompatibility is overcome, but LaB6 emitter contamination occurs during operation
Solution Approach 1:
The invention removes the graphite paste bonding material from the emitter assembly, eliminating the contamination source. Direct bonding methods are employed that prevent carbon or graphite contaminants from migrating to the LaB6 emitter surface during operation
Solution Approach 2:
The invention employs a disposable protective coating or sacrificial layer that prevents contamination of the LaB6 emitter. This protective layer can be easily applied and removed or replaced, ensuring the emitter remains clean during operation
3Device complexity
If direct bonding of LaB6 to support is used, then structural simplicity is achieved, but erosion occurs due to material incompatibility
Solution Approach 1:
The invention employs composite material structures at the bonding interface, combining LaB6 with compatible materials such as tungsten or tungsten alloys that resist erosion. The composite structure maintains simplicity while providing erosion resistance through material compatibility
Solution Approach 2:
The invention applies localized material modifications or coatings at the bonding interface between LaB6 and support. The local quality of the interface is enhanced with erosion-resistant materials or surface treatments, while the rest of the structure remains simple and direct
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 adapter-filament-electrode assembly achieves mechanical stability, withstands high temperatures, and maintains ultra-high vacuum conditions, reducing erosion and contamination, thereby extending the lifetime and performance of the electron source.
Implementation Method 1
Fusion zones can be formed by spot welding or laser welding without filler material
Implementation Method 2
Fusion zones can be formed by spot welding or laser welding without filler material
Implementation Method 3
a tantalum adapter can be formed by deposition onto the filament
Data Source
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.