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, leading to premature emitter failure due to high emission currents, which limits image quality and the useful life of the X-ray source.
Innovation Solution
An X-ray tube design featuring a cathode assembly with a pair of emission surfaces angled relative to each other, a focusing electrode, and an extraction electrode that can be adjusted between positive and negative bias, along with a magnetic assembly for directing the electron beam, allowing for higher emission currents without compromising the tube's 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 increased temperature and accelerated burnout
Solution Approach 1:
The emitter is divided into multiple separate emission surfaces (e.g., multiple filaments or cathode segments) instead of a single emitter. This segmentation allows the total emission current to be distributed across multiple surfaces, reducing the thermal load and space charge effects on each individual surface while maintaining the required total electron beam intensity, thereby extending emitter lifespan
Solution Approach 2:
The emission surfaces are arranged in a three-dimensional configuration (e.g., angled relative to the electron beam axis, distributed across different positions) rather than a single planar surface. This spatial distribution reduces the density of emission current on each surface and allows for better thermal management and reduced space charge repulsion effects
2Speed
If the electron beam current is rapidly changed to control intensity, then the temporal resolution and image quality are improved, but the focusing and positioning of the electron beam becomes difficult due to space charge force changes
Solution Approach 1:
Focusing electrodes and magnetic fields are pre-configured to compensate for expected space charge effects at different emission current levels. The electrostatic and magnetic focusing systems are designed in advance to maintain beam focus despite rapid current changes, eliminating the need for real-time adjustment during operation
Solution Approach 2:
Electrostatic emission control electrodes (such as grids or control electrodes positioned near the emission surfaces) are introduced as intermediaries to modulate the electron beam intensity. These control electrodes allow for rapid current adjustment while the magnetic and electrostatic focusing systems work together to maintain beam focus, decoupling the intensity control from the focusing control
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 precise control of electron beam intensity and position, extending the X-ray tube's useful life and maintaining image quality by accommodating larger emission currents while reducing thermal stress and space charge effects.
Implementation Method 1
a cathode assembly on which is disposed a pair of emission surfaces for generating a pair of electron beams
Implementation Method 2
a focusing electrode adjacent the cathode assembly for focusing the electron beams
Implementation Method 3
a magnetic assembly spaced from the extraction electrode opposite the focusing electrode for focusing the electron beams towards the target
Implementation Method 4
an extraction electrode spaced from the focusing electrode opposite the cathode assembly for controlling an intensity of the electron beams, wherein the extraction electrode can be adjusted between a positive and negative bias with respect to the emission surfaces
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 emission surfaces for generating an electron beam, where the pair of emission surfaces are disposed in the cathode assembly 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 by adjustment of a positive or negative biasing voltage applied to the extraction electrode, 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.