Thermally Isolated Repeller Spokes and Hollow Post
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Solution Overview
Problem
In ion sources, particularly indirectly heated cathode (IHC) ion sources, maintaining high temperatures for repellers and electrodes is challenging due to thermal conduction and radiation losses, which limits their operational temperature and efficiency.
Innovation Solution
A thermally isolated repeller design featuring a repeller disk with spokes instead of a central stem and a hollow post, along with radiation shields on the back surface, reduces thermal conduction and radiation emission, allowing for increased temperature maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the repeller and electrodes are physically attached to metal clamps affixed to the arc chamber base, then the components are securely held in place, but thermal conduction draws heat away from these components causing them to operate at lower temperatures than desired
Solution Approach 1:
The repeller is segmented into a repeller disk and a post structure with multiple thin spokes rather than a solid stem. This segmentation reduces the cross-sectional area for thermal conduction while maintaining structural integrity and electrical connectivity.
Solution Approach 2:
The post is designed with varying cross-sectional properties - hollow in the lower portion and solid in the upper portion - to optimize the balance between thermal isolation and mechanical strength. The hollow section provides superior thermal blocking while the solid section ensures adequate structural support.
2Strength
If a solid central stem is used to support the repeller disk, then structural support is maximized, but thermal conduction from the repeller disk to the post is increased
Solution Approach 1:
The solid central stem is replaced with multiple discrete thin spokes radiating from the post to the repeller disk. This segmentation reduces the total thermal conduction path area while distributing mechanical loads effectively across multiple support points.
Solution Approach 2:
The support structure transitions from a one-dimensional central stem to a radial spoke configuration, distributing thermal and mechanical pathways across multiple dimensions. This geometric transformation reduces thermal conduction while maintaining structural rigidity.
3Loss of substance
If the repeller operates at high temperature to minimize deposition, then material deposition within the chamber is reduced, but thermal radiation losses increase
Solution Approach 1:
The hollow post structure, while primarily designed for thermal isolation, also creates a radiation trap effect where thermal radiation from the repeller disk is partially reflected back toward the disk by the hollow cavity walls, converting what would be energy loss into useful heating.
Solution Approach 2:
The post structure varies its thermal and radiative properties along its length - hollow in the lower section for maximum thermal isolation and radiation trapping, solid in the upper section for structural support - creating localized zones with optimized properties for different functions.
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 new design increases the repeller's temperature by more than 100°C, enhancing operational efficiency and reducing material deposition within the ion source chamber.
Implementation Method 1
The use of spokes rather than a central stem may reduce the thermal conduction from the repeller disk to the post. By incorporating a hollow post, the thermal conduction is further reduced.
Implementation Method 2
In certain embodiments, radiation shields are provided on the back surface of the repeller disk to reduce the amount of radiation emitted from the sides of the repeller disk.
Implementation Method 3
The filament emits thermionic electrons, which are accelerated toward and heat the cathode, in turn causing the cathode to emit electrons into the chamber of the ion source.
Data Source
AI summary
An ion source having a thermally isolated repeller is disclosed. The repeller comprises a repeller disk and a plurality of spokes originating at the back surface of the repeller disk and terminating in a post. In certain embodiments, the post may be hollow through at least a portion of its length. The use of spokes rather than a central stem may reduce the thermal conduction from the repeller disk to the post. By incorporating a hollow post, the thermal conduction is further reduced. This configuration may increase the temperature of the repeller disk by more than 100° C. In certain embodiments, radiation shields are provided on the back surface of the repeller disk to reduce the amount of radiation emitted from the sides of the repeller disk. This may also help increase the temperature of the repeller. A similar design may be utilized for other electrodes in the ion source.