Angled Flat Emitter Cathode for X-ray Tube Beam Control
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Solution Overview
Problem
Current X-ray tubes in CT systems fail to control electron beam intensity with desired temporal resolution and suffer from premature emitter failure due to high emission currents, limiting image quality and the useful life of the X-ray source.
Innovation Solution
The X-ray tube employs a cathode assembly with a pair of angled flat emitters and a magnetic focusing assembly, where the extraction electrode controls the electron beam intensity and is maintained at a positive bias voltage, allowing for higher emission currents without compromising the emitter lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher emission currents are used to improve image quality and system performance, then the electron beam intensity and X-ray output are improved, but the emitter lifespan is reduced due to accelerated burnout from increased temperature
Solution Approach 1:
The single emitter is divided into multiple segmented emitters (e.g., three emitters arranged in a triangular configuration). Each emitter operates at a lower individual current, reducing thermal stress and extending lifespan, while the combined electron beam from all segments achieves the required total intensity for high-quality imaging.
2Speed
If the electron beam current is rapidly changed to improve temporal resolution, then the control responsiveness is improved, but the focusing and positioning accuracy deteriorates due to space charge force changes
Solution Approach 1:
A focusing electrode is positioned close to the emitter to pre-focus the electron beam before it enters the magnetic focusing assembly. This preliminary focusing action ensures that even during rapid current changes, the beam maintains proper convergence, allowing fast temporal response without sacrificing focusing accuracy.
3Ease of operation
If a wire mesh grid is introduced to control beam current, then the current control capability is improved, but the grid reliability deteriorates due to thermo-mechanical stresses from high energy electron beam interception
Solution Approach 1:
The problematic wire mesh grid is completely removed from the system. Instead, electrostatic control electrodes are used to modulate the electron beam current. These electrodes create electric fields that control beam intensity without physically intercepting the high-energy electron stream, eliminating thermo-mechanical stress issues while maintaining precise current control 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
This configuration enables effective focusing and positioning of the electron beam, extending the useful life of the X-ray tube and maintaining image quality by accommodating larger emission currents within normal energy ranges.
Implementation Method 1
at least one extraction electrode for controlling an intensity of the electron beam, wherein the at least one extraction electrode is maintained at a positive bias voltage with respect to the emitters
Implementation Method 2
a magnetic assembly located between the injector and the target for directionally influencing focusing, deflecting and/or positioning the electron beam towards the target
Implementation Method 3
a magnetic assembly located between the injector and the target for directionally influencing focusing, deflecting and/or positioning the electron beam towards the target
Implementation Method 4
a pair of angled, flat emitters that each emit streams of electrons that can combine to form an electron beam
Data Source
AI summary
In the present invention, a computed tomography system, an X-ray tube used therein and a cathode assembly disposed in the X-ray tube, as well as an associated method of use, is provided that includes a gantry and the X-ray tube coupled to the gantry. The X-ray tube includes the cathode assembly having a pair of emitters for generating an electron beam, where the pair of emitters are disposed in the casing at angles with respect to one another. The X-ray tube further includes a focusing electrode for focusing the electron beam, an extraction electrode which electrostatically controls the intensity of the electron beam, a target for generating X-rays when impinged upon by the electron beam and a magnetic focusing assembly located between the cathode assembly and the target for focusing the electron beam towards the target.