X-Ray Tube Filament Layout to Shield the Output Window
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Solution Overview
Problem
The adhesion of metal atoms desorbed from the filament to the output window in an X-ray tube reduces X-ray transmittance and can generate impure X-rays, degrading the tube's performance.
Innovation Solution
The positional relationship between the output window, focusing electrode, and filament is adjusted such that metal atoms desorbed from the filament are shielded by the focusing electrode, reducing their adhesion to the output window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the filament is positioned in a conventional arrangement, then the X-ray tube structure is simple, but metal atoms desorbed from the filament adhere to the output window, reducing X-ray transmittance and generating impure X-rays
Solution Approach 1:
The patent positions the filament asymmetrically relative to the output window and focusing electrode, specifically placing the center of the filament on the opposite side of the first line (which passes through the output window center and is tangent to the focusing electrode end) compared to conventional symmetric arrangements. This asymmetric positioning creates a geometric configuration where the focusing electrode effectively shields the output window from metal atom deposition, resolving the contradiction between maintaining simple structure and preventing metal atom adhesion.
Solution Approach 2:
The focusing electrode serves as an intermediary element that blocks the path of metal atoms desorbed from the filament. By strategically positioning the filament and focusing electrode, the focusing electrode acts as a physical barrier that intercepts metal atoms before they can reach the output window, thereby protecting the output window without requiring additional protective components.
2Ease of operation
If the filament is surrounded by the focusing electrode which is surrounded by the envelope, then the focusing function is improved, but metal atoms desorbed from the filament can diffuse inside the envelope and adhere to the output window
Solution Approach 1:
The focusing electrode serves as an intermediary element that blocks the path of metal atoms desorbed from the filament. By strategically positioning the filament and focusing electrode, the focusing electrode acts as a physical barrier that intercepts metal atoms before they can reach the output window, thereby protecting the output window without requiring additional protective components.
Solution Approach 2:
The patent changes the spatial parameters (positioning) of the filament relative to the focusing electrode and output window. Specifically, the center of the filament is positioned at a specific location relative to the first line, creating optimal geometric relationships that simultaneously maintain focusing performance and prevent metal atom adhesion to the output window.
3Device complexity
If metal atoms adhere to the output window, then the structure remains unchanged, but the characteristic X-ray intensity is reduced and impure X-rays are generated
Solution Approach 1:
The patent implements preliminary action by positioning the filament and focusing electrode in a specific geometric relationship before operation begins. This pre-configured arrangement ensures that during X-ray tube operation, the focusing electrode automatically shields the output window from metal atom deposition, preventing the degradation of X-ray quality before it can occur.
Solution Approach 2:
The patent positions the filament asymmetrically relative to the output window and focusing electrode, specifically placing the center of the filament on the opposite side of the first line (which passes through the output window center and is tangent to the focusing electrode end) compared to conventional symmetric arrangements. This asymmetric positioning creates a geometric configuration where the focusing electrode effectively shields the output window from metal atom deposition, resolving the contradiction between maintaining simple structure and preventing metal atom adhesion.
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 configuration minimizes the reduction of characteristic X-ray intensity and the generation of impure X-rays, ensuring the X-ray tube maintains performance over extended use.
Implementation Method 1
thermions are generated in the filament located at the cathode structure when a negative voltage is applied to the cathode structure
Implementation Method 2
metal atoms (e.g., tungsten atoms) included in the filament evaporate and desorb from the filament
Implementation Method 3
some of the metal atoms desorbed from the filament may diffuse inside the envelope
Implementation Method 4
the trajectory of the thermions is bent by an electric field generated by the envelope and the focusing electrode
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An X-ray tube includes an envelope, a plate-shaped output window located at an end of the envelope, a target facing the output window inside the envelope, a tubular focusing electrode surrounding the target inside the envelope, and a filament surrounding the focusing electrode inside the envelope. A first line is defined to pass through a center of a surface of the output window at the target side and to be tangent to an end of the focusing electrode at the output window side; and a center of the filament is positioned at the same side of the first line as the focusing electrode.