Segmented Cathode Header Optic for X-Ray Tube
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Solution Overview
Problem
Miniature x-ray tubes face challenges in producing a spot size smaller than the emitter due to variations in filament shape and position, leading to inconsistent x-ray emissions, and require improved manufacturing tolerances, energy efficiency, and cost-effectiveness.
Innovation Solution
A cathode header optic with an elongate trench and cup recess design that houses a low-power, low-mass tungsten filament, combined with a secondary cathode optic to focus the electron beam, achieving a spot size smaller than 200 microns and enhancing manufacturing robustness and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a T-slot optic is used to focus electrons in a miniature x-ray tube, then electron beam focusing is achieved, but manufacturing dimensional tolerances become difficult to maintain due to filament position and shape variations
Solution Approach 1:
The optic is segmented into multiple discrete elements (first optic element and second optic element) positioned at different locations relative to the filament. This segmentation allows each element to be manufactured and positioned independently, reducing the cumulative tolerance stacking problem that plagues monolithic T-slot designs. The first optic element focuses electrons from one region of the filament while the second element addresses variations from other regions, collectively achieving consistent beam spot dimensions despite filament manufacturing variations.
Solution Approach 2:
Different regions of the filament are addressed with different optic elements having potentially different geometric properties. The first optic element is positioned to optimally focus electrons from a first region of the filament, while the second optic element addresses a second region. This local optimization approach ensures that each region's contributions to the beam spot are minimized, achieving overall consistency without requiring ultra-precise control of the entire filament structure.
2Length of moving object
If the filament dimensions are reduced to enable miniature x-ray tube operation, then device size is reduced, but the impact of filament shape and position variations on beam spot size increases
Solution Approach 1:
The filament is treated as a distributed source with multiple regions, each addressed by a dedicated optic element. This segmentation strategy transforms the problem from controlling the entire filament's position and shape to controlling multiple smaller regions independently. Even though the filament is miniaturized, the segmented optic approach ensures that variations in any single region have limited impact on the overall beam spot, thereby maintaining manufacturing precision despite small dimensions.
Solution Approach 2:
The multiple optic elements act as intermediaries between the miniaturized filament and the beam spot. Rather than requiring direct, precise control of the filament's position and shape, the optic elements serve as mediating structures that capture and redirect electrons from different filament regions. This intermediary approach decouples the beam spot quality from the filament manufacturing precision, allowing miniaturization without sacrificing beam spot control.
3Productivity
If a conventional single-optic design is used, then device complexity is low, but electron efficiency and spot size control are insufficient for miniature x-ray tubes
Solution Approach 1:
The electron optics are segmented into multiple functional elements rather than using a single monolithic structure. This segmentation enables each element to be optimized for specific regions of the filament, improving overall electron efficiency by capturing and focusing electrons more effectively from all filament regions. The moderate increase in structural complexity is justified by the significant improvement in electron utilization and beam spot quality.
Solution Approach 2:
The multiple optic elements collectively perform the universal function of focusing electrons from the entire filament while individually addressing specific regional variations. This multi-functional approach allows the optic system to simultaneously achieve beam focusing, variation compensation, and efficiency optimization, making the increased complexity worthwhile for achieving superior performance in miniature x-ray tubes.
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 design achieves a reduced electron beam cross-section, improved x-ray flux, and increased manufacturing tolerances, making the x-ray tube more energy-efficient, robust, and cost-effective, while maintaining a focused spot size and reducing the impact of filament variations.
Implementation Method 1
Thermionic emission is a very common strategy for obtaining electrons for use in x-ray producing devices. For thermionic electron emission to take place, a source material is heated to high temperature in an evacuated environment in order to impart sufficient energy to bound electrons within the material to liberate them.
Implementation Method 2
In a miniature x-ray device, an electric or magnetic field is commonly used to focus the emitted electrons into a beam, directed toward an anode target. The beam of emitted electrons is thereby focused to a desired cross-section at a point in space on or near an anode target.
Data Source
AI summary
A cathode header optic for an x-ray tube includes an elongate trench with opposite trench walls. A cup recess is formed in the trench between the opposite trench walls, and has a bounded perimeter. A cathode element is disposed in the trench at the cup recess. The cathode element is capable of heating and releasing electrons. A secondary cathode optic defining a cathode ring can be disposed about the header optic. The cathode optics can form part of an x-ray tube.