Flat Emitter Stress Compensation for X-ray Tube Reliability
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Solution Overview
Problem
Existing X-ray tube emitters face deformation and electrical shorts due to high centrifugal forces and thermal expansion at elevated temperatures, reducing their operational lifespan and image quality.
Innovation Solution
Incorporating stress compensation features such as compliant regions, sliding structures, and thermal expansion compensation mechanisms within the emitter or its support structure to mitigate thermal and centrifugal stresses, allowing for longer emission areas and higher rotation speeds without electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the emitter operates at high temperatures above 2000°C to produce electron emission, then electron emission capability is improved, but thermal expansion causes slots to close and adjacent ribbons to contact, creating electrical shorts
Solution Approach 1:
The patent applies thermal expansion principle by designing the emitter with slots that are intentionally configured to accommodate thermal expansion of the emitter material at high operating temperatures. The slots are designed with specific geometries and spacing that allow the emitter to expand without causing the slots to close completely or adjacent ribbons to contact, thereby preventing electrical shorts while maintaining electron emission capability above 2000°C
2Speed
If the emitter is subjected to high centrifugal forces in excess of 30 G during rotation, then imaging speed is improved, but the emitter deforms in the direction of centrifugal force causing slots to close and electrical shorts
Solution Approach 1:
The patent applies the counterweight principle by designing support structures and anchoring mechanisms that provide opposing forces to counteract the centrifugal forces acting on the emitter during high-speed rotation. The emitter is supported at multiple points including ends and intermediate positions, with structures specifically configured to resist deformation in the direction of centrifugal force, thereby preventing slot closure and electrical shorts while enabling rotation at centrifugal forces in excess of 30 G
3Measurement precision
If the emitter uses long emissive lengths to improve image resolution, then imaging quality is improved, but the combination of long length, high temperature, and high centrifugal force increases stress beyond material strength causing deformation
Solution Approach 1:
The patent applies segmentation by dividing the long emitter into multiple sections with intermediate support structures. The emitter is supported at multiple points along its length, including ends and intermediate positions, which breaks the continuous long span into shorter segments. This reduces the stress on any single section while maintaining the overall long emissive length needed for high-resolution imaging, preventing deformation under the combined effects of high temperature and centrifugal force
4Measurement precision
If the slots are made narrower to improve emission profile, then electron emission precision is improved, but the slots are more susceptible to closing due to thermal expansion and centrifugal force causing electrical shorts
Solution Approach 1:
The patent addresses this by designing slot geometries that account for thermal expansion. The slots are configured with specific width, depth, and curvature characteristics that allow them to maintain functional precision for electron emission while accommodating the expansion of adjacent ribbons at high temperatures. The slot design ensures that even with thermal expansion and centrifugal force, the slots do not close completely, preventing electrical shorts while maintaining narrow slot benefits for emission profile precision
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 prolongs the life of X-ray tubes by preventing electrical shorts and enabling longer emission areas and higher emission speeds with reduced maintenance needs.
Implementation Method 1
Some of the released electrons may impact the target anode. The collision of the electrons with the target anode produces X-rays... In thermionic cathode systems, an emitter is included that may be induced to release electrons through the thermionic effect, i.e. in response to being heated.
Implementation Method 2
The high operating temperatures at which the emitter is operated also induce thermal strains due to the thermal expansion of the emitter exceeding the thermal expansion of the lower temperature sub-structure.
Implementation Method 3
When the X-ray tube is rotated around the object being imaged, the centrifugal forces exerted on the emitter can be in excess of 30 G.
Data Source
AI summary
A flat emitter for uses within an x-ray tube is formed of an electron emissive material that includes one or more stress compensation features capable of reducing the total stress in the flat emitter due to thermal expansion and/or centrifugal acceleration force. The one or more stress compensation features of the flat emitter for reducing the total stress in the flat emitter are formed directly on the flat emitter, are formed on the support structure for the flat emitter and connected to the flat emitter, or a combination thereof.