Planar Filament Geometry for Focused X-Ray Electron Emission
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Solution Overview
Problem
Existing x-ray sources face challenges in efficiently focusing electron emission and stabilizing the filament, leading to uneven heating and potential premature failure at vulnerable locations.
Innovation Solution
A planar filament with varying cross-sectional areas and shapes, including a wider and thinner center-region, is designed to concentrate electron emission and stabilize the filament, achieved through regions with different thicknesses and widths, and smooth transitions between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform filament design is used, then the manufacturing process is simple, but electron emission is uneven and the filament is unstable
Solution Approach 1:
The filament is designed with non-uniform cross-sectional areas where different regions have different thicknesses. The center region has a larger cross-sectional area than the end regions, creating local variations in electrical resistance and heat distribution. This local quality differentiation concentrates electron emission in the center region while providing structural stability, resolving the contradiction between uniform manufacturing and non-uniform performance.
2Reliability
If the filament has a larger cross-sectional area throughout, then it is more stable, but electron emission is less focused and the focal spot is larger
Solution Approach 1:
The filament implements local quality by having the center region with a larger cross-sectional area than the end regions. This creates a specific resistance distribution where the center region has lower resistance, concentrating electron emission in that area. The result is a focused electron beam with a smaller focal spot while maintaining overall filament stability through the larger center cross-section.
3Manufacturing precision
If the filament has a smaller cross-sectional area, then the focal spot is smaller, but the filament is less stable and heats unevenly
Solution Approach 1:
The filament design uses local quality differentiation where the center region has a larger cross-sectional area to provide stability and proper heat distribution, while the end regions have smaller cross-sectional areas. This configuration allows the center to maintain a small focal spot for high precision while the overall filament structure remains stable and resistant to uneven heating through the strategically placed larger center section.
4Manufacturing precision
If the electron emission is concentrated in one area, then the focal spot is smaller, but the filament experiences uneven heating and potential failure
Solution Approach 1:
The filament design concentrates electron emission in the center region by giving it a larger cross-sectional area, which creates a focused focal spot. Simultaneously, the smaller end regions are designed to handle lower current densities, preventing excessive heat generation at the ends. This local quality differentiation manages heat distribution across the filament, concentrating emission where needed while preventing harmful uneven heating that would lead to premature failure.
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
This design enhances focused electron emission, increases the rate of temperature rise, and stabilizes the filament, resulting in a more efficient and durable x-ray source with a smaller focal spot.
Implementation Method 1
A large voltage between a cathode and an anode of the x-ray tube, and sometimes a heated filament, can cause electrons to emit from the cathode to the anode
Implementation Method 2
A large voltage between a cathode and an anode of the x-ray tube, and sometimes a heated filament, can cause electrons to emit from the cathode to the anode
Implementation Method 3
The anode can include a target material. The target material can generate x-rays in response to impinging electrons from the cathode
Data Source
AI summary
A planar filament for an x-ray tube can have a different cross-sectional area at different locations. In regions of smaller cross-sectional area, there can be higher current density, and thus increased heating and higher temperature of the wire. In regions of larger cross-sectional area, there can be lower current density, and thus decreased heating of the wire. Regions of larger cross-sectional area can also be stronger, thus reducing early filament failures. Wider regions can have increased area for electron emission. By adjusting the cross-sectional area and width of the wire at different locations, electron emission can be largely confined to a center of the filament, and filament life can increase.