X-ray tube with emission loop and beam guide
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Solution Overview
Problem
Existing X-ray tubes with coiled tungsten filaments suffer from poor spectral stability at low high-voltage settings and are not suitable for applications requiring small focal spots and high emission current, while X-ray tubes with emission loops are limited to applications without high resolution due to their large, annular focal spots.
Innovation Solution
An X-ray tube design featuring a cathode with an emission loop and an electron beam guide that shapes the electron trajectory to irradiate a solid area of the anode, rather than a hollow one, allowing for high emission current with minimal impact on output stability, using a refractory metal wire and a coating like barium oxide to reduce electron emission temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a coiled tungsten filament is used to achieve a small focal spot, then the focal spot size is reduced and brilliance is improved, but spectral stability deteriorates at low high-voltage settings
Solution Approach 1:
The patent changes the operating parameters by using a coated emission loop instead of a coiled tungsten filament, enabling operation at lower temperatures that reduce tungsten vaporization while maintaining small focal spot size. This parameter change resolves the contradiction between achieving small focal spot and maintaining spectral stability at low high-voltage settings
Solution Approach 2:
The patent employs a composite cathode structure consisting of a coated emission loop where a low-work-function coating is applied to the loop surface. This composite material approach enables efficient electron emission at lower temperatures, preventing tungsten vapor deposition on the anode while maintaining small focal spot dimensions, thus resolving the spectral stability issue
2Power
If the filament current is increased to maximize power at low high-voltage settings, then the emission current is improved, but tungsten vaporization increases and deposits on the anode, worsening spectral stability
Solution Approach 1:
The patent changes the emission mechanism by using a coated emission loop that provides efficient thermionic emission at lower temperatures. This parameter change allows achieving high emission current without excessive temperature increase, thereby preventing tungsten vaporization and maintaining spectral stability at low high-voltage settings
Solution Approach 2:
The low-work-function coating on the emission loop serves as a sacrificial layer that enables prolonged operation at lower temperatures. The coating material is consumed gradually, allowing the tube to maintain stable performance for extended periods without the tungsten filament itself degrading rapidly
3Power
If an emission loop is used to achieve high emission current, then the emission current is improved, but the focal spot becomes large and annular, worsening manufacturing precision
Solution Approach 1:
The patent introduces an electron beam guide component that adds a new dimensional control element to the electron trajectory. This guide structure confines the electrons emitted by the loop into a focused beam that converges on a small focal spot area, transforming the natural annular emission pattern into a concentrated spot while preserving high emission current capability
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
Enables the formation of a small, solid focal spot with high emission current and improved spectral stability at low high-voltage settings, allowing for efficient operation across a range of applications.
Implementation Method 1
Electrons are emitted by thermionic emission from the cathode, by resistively heating a filament
Implementation Method 2
an electron beam guide configured to cause electrons emitted by the emission loop to irradiate an area of the target surface of the anode
Implementation Method 3
Electrons from the cathode are accelerated towards the anode by an electric field and generate X-rays on collision with the anode
Data Source
AI summary
The present invention relates to an X-ray tube for X-ray analysis. The X-ray tube comprises an anode having a target surface and a cathode. The cathode comprises an emission loop. The emission loop extends around an axis that passes through the anode, and the cathode and the anode are spaced apart from one another along the axis. Electrons emitted from the cathode irradiate the target surface of the anode to produce X-rays. The X-ray tube further comprises an electron beam guide. The electron beam guide is configured to guide electrons emitted by the cathode, so as to irradiate an area of the anode. The irradiated area is enclosed by a single boundary.