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 due to high thermal stress, leading to increased downtime and material degradation, and there is a need for a more efficient and durable solution that can be used across various ion source arrangements.
Innovation Solution
An indirectly heated cathode ion source assembly featuring a cup-shaped cathode with a thermal barrier composed of concentric cylindrical foils to minimize thermal loss, a holder with a bayonet connection for secure mounting, and a graphite support plate with a thermal shield spacer, all designed to maintain high temperatures and reduce erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a heated filament cathode is used to generate thermal electrons, then ionization efficiency is improved, but thermal stress and erosion increase leading to reduced service life
Solution Approach 1:
The cathode assembly is segmented into separate functional components: the cathode body, the filament, and the thermal barrier. This segmentation allows the filament to be heated to high temperatures for efficient electron emission while the thermal barrier protects the cathode body from excessive thermal stress, thereby extending its service life.
Solution Approach 2:
A thermal barrier is introduced as an intermediary component between the heated filament and the cathode body. This thermal barrier mediates the thermal interaction, allowing the filament to operate at high temperatures for efficient ionization while preventing excessive heat from damaging the cathode structure, thus resolving the contradiction between ionization efficiency and service life.
2Power
If high thermal stress is applied to the cathode, then electron emission efficiency is improved, but material degradation and erosion increase
Solution Approach 1:
Different parts of the cathode assembly have different thermal properties. The filament is designed to withstand high temperatures for efficient electron emission, while the cathode body and thermal barrier are designed to resist thermal stress and prevent material degradation. This local differentiation of thermal qualities allows high power operation without excessive erosion.
3Ease of manufacture
If a threaded connection is used to mount the cathode, then assembly is simplified, but alignment precision and secure mounting are compromised
Solution Approach 1:
The cathode mounting system uses a dynamic bayonet connection that allows for self-alignment during assembly. The connection mechanism incorporates movable elements that automatically adjust to achieve precise alignment when the cathode is inserted and locked into place, combining ease of assembly with high alignment precision.
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 enhances cathode assembly performance by maintaining high temperatures for improved thermal electron emission, reducing erosion, and minimizing downtime, while being adaptable to different ion source systems.
Implementation Method 1
A filament is supported within the tubular body and emits electrons that heat the endcap through electron bombardment, thermionically emitting the ionizing electrons into gas confinement chamber
Implementation Method 2
emits electrons that heat the endcap through electron bombardment, thermionically emitting the ionizing electrons into gas confinement chamber
Implementation Method 3
a thermal barrier having a plurality of cylindrical foils concentric to the periphery of the cathode to reduce thermal loss
Data Source
AI summary
The indirectly heated cathode ion source assembly employs a cathode having a cup shaped body with a base and a cylindrical periphery, a thermal barrier having a plurality of cylindrical foils concentric to the cathode to reduce thermal loss; and a holder receiving the cathode and the thermal barrier in concentric relation.