Septum Rod Electrode for X-ray Tube Cathode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional X-ray tubes with cylindrically wound filaments face challenges in achieving uniform focal spots due to complex electron emission patterns, requiring tight manufacturing and positioning tolerances, and those with flat emitters require high grid voltages, making them costly and difficult to construct within typical bias voltage limits.
Innovation Solution
A cathode assembly with flat emitters and a septum or rod-like feature in the width electrode assembly allows for increased emission currents and reduced aspect ratios, enabling operation within typical bias voltages of +/â10 kV for both grid and focus electrodes, allowing for large and small focal spots by adjusting bias voltages and the position of the focal spot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cylindrically wound filaments are used, then electron emission is achieved, but the emission pattern is complex and non-uniform, requiring tight manufacturing and positioning tolerances
Solution Approach 1:
The cathode is divided into multiple separate planar emitters rather than using a single continuous cylindrical filament. Each planar emitter has a simple flat geometry that emits electrons uniformly, and the multiple emitters are arranged in a specific pattern within the cathode cup. This segmentation allows each emitter to be manufactured and positioned independently with relaxed tolerances while achieving uniform overall electron emission.
Solution Approach 2:
Instead of using a cylindrical geometry (traditional approach), the invention inverts to planar flat surfaces for the emitters. This geometric inversion simplifies the emission pattern from complex three-dimensional cylindrical emission to uniform two-dimensional planar emission, significantly reducing sensitivity to positioning tolerances and improving focal spot uniformity.
2Ease of manufacture
If flat emitters are used, then manufacturing cost is reduced and positioning tolerance is relaxed, but high grid voltages are required exceeding typical bias voltage limits
Solution Approach 1:
A grid electrode is introduced as an intermediary between the planar emitters and the anode. This grid electrode, with its specific aperture pattern and positioning, mediates the electron flow from the planar emitters, enabling effective electron beam control and focal spot formation at reduced grid voltages that fall within typical bias voltage limits, while maintaining the manufacturing advantages of planar emitter geometry.
3Manufacturing precision
If cathodes are seated deeper in the cup, then sufficient distance is provided for electron focusing, but the distance between cathode and anode increases beyond optimal values
Solution Approach 1:
The invention transitions from the traditional deep-seating approach (one-dimensional positioning adjustment) to a multi-dimensional solution involving planar emitter geometry, specific emitter arrangement patterns, and grid electrode configuration. This dimensional change allows for effective electron focusing at optimal cathode-to-anode distances by controlling electron trajectories through the grid apertures rather than relying solely on deep cathode seating.
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
The solution enhances the effective emission area, reduces manufacturing costs, and maintains filament life while achieving stable and focused electron beams within standard voltage limits, improving the reliability and construction of X-ray tubes.
Implementation Method 1
a filament is included that may be induced to release electrons through the thermionic effect, i.e. in response to being heated
Implementation Method 2
an electron beam from an emitter that is accelerated using a high voltage applied across a cathode-to-anode vacuum gap to produce x-rays upon impact with the anode
Data Source
AI summary
In the present invention, a cathode assembly for an X-ray tube is provided including a cathode cup, a pair of emitters disposed within the cup and each configured to emit an electron beam therefrom and an electrode spaced from the pair of emitters and configured to affect the shape and/or intensity of the electron beams emitted by the pair of emitters. The electrode includes a rod extending across a central aperture defined within the electrode that enables the electrode to grid or focus the electron beam or beams emitted from the emitters using a bias voltage between +10 kV and â10 kV.