Indirectly Heated Cathode Ion Source Thermal Barrier
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Solution Overview
Problem
Existing ion implanter cathode assemblies face issues with reduced performance and erosion during ion beam operation, leading to increased downtime and the need for improved thermal electron emission and reduced part count.
Innovation Solution
An indirectly heated cathode ion source assembly featuring a tungsten cathode cup unit with a thermal barrier system, including concentric cylindrical foils acting as thermal breaks, and a coaxially positioned filament for enhanced thermal electron emission and reduced thermal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional heated filament cathode is used in an ion source, then ion beam generation is achieved, but thermal losses increase and cathode life is reduced due to erosion
Solution Approach 1:
The cathode assembly is segmented into distinct functional components: the filament (electron source), the cathode cup (emission surface), and the thermal barrier (insulation layer). This segmentation allows each component to perform its specific function optimally while reducing thermal coupling between parts, thereby reducing thermal losses and extending cathode life.
Solution Approach 2:
A thermal barrier (insulation layer) is introduced as an intermediary between the heated filament and the cathode cup. This intermediary reduces direct thermal transfer, allowing the cathode to operate at optimal temperatures with reduced thermal losses, thereby improving reliability and reducing energy waste.
2Productivity
If the cathode operates at high temperature to improve electron emission, then thermal electron emission efficiency increases, but cathode erosion accelerates
Solution Approach 1:
The cathode assembly employs local quality by maintaining different temperature zones in different regions: the filament operates at high temperature for efficient electron emission, while the cathode cup operates at a controlled temperature optimized for electron emission efficiency. The thermal barrier ensures that high temperature is localized to the filament region only, preventing excessive heating of the cathode cup and reducing erosion while maintaining emission efficiency.
3Temperature
If multiple separate components are used in the cathode assembly to manage thermal properties, then thermal control is improved, but device complexity increases
Solution Approach 1:
The thermal barrier is integrated directly with the cathode cup structure, forming a unified cathode assembly component. This merging approach maintains effective thermal control by keeping the insulation layer in direct thermal contact with the cathode cup, while reducing assembly complexity by eliminating separate mounting structures and simplifying the overall assembly process.
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 assembly achieves high temperature operation, improving thermal electron emission efficiency, extending cathode life, and reducing ion implanter downtime by minimizing thermal losses and cathode erosion.
Implementation Method 1
A filament is provided within the cathode cup unit and spaced from the body of the cathode cup unit a predetermined distance for generating thermal electrons
Implementation Method 2
An indirectly heated cathode ion source assembly featuring a tungsten cathode cup unit with a thermal barrier system, including concentric cylindrical foils acting as thermal breaks
Data Source
AI summary
The indirectly heated cathode ion source assembly employs a cathode cup unit and filament arrangement wherein the filament has a flat face spaced from a tungsten disc-shaped body and is disposed in a space that is surrounded by a thermal barrier to reduce thermal losses. The thermal barrier is formed by a plurality of concentric foils that are closely spaced.