Emitter Deep Structuring for X-ray Tube Lifetime
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Solution Overview
Problem
The lifetime of thermal electron emitters in X-ray tubes is limited by material evaporation, and increasing thickness or reducing temperature to extend life results in challenges such as increased heating currents, thermal inertia, and difficulties in focusing the electron beam.
Innovation Solution
The emitter features deep structuring on its surface, creating additional emission surfaces at angles, which reduces temperature without enlarging the horizontal surface, allowing for increased lifetime without affecting electron beam focusing, and can be implemented in both directly and indirectly heated emitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the material thickness of the emitter is increased to extend lifetime, then the lifetime is improved, but the heating current and thermal inertia increase
Solution Approach 1:
The patent applies deep structuring to the emitter surface, creating three-dimensional microstructures (grooves, pits, or protrusions) that increase the effective emission surface area without increasing the lateral dimensions of the emitter. This dimensional transformation from a flat two-dimensional surface to a three-dimensional textured surface allows the emitter to achieve higher electron emission capability while maintaining the same physical footprint, thereby extending lifetime without proportionally increasing heating current requirements
2Duration of action of stationary object
If the emitter temperature is reduced to extend lifetime, then the lifetime is improved, but the emission surface area must be enlarged
Solution Approach 1:
By creating deep microstructures on the emitter surface, the patent effectively increases the emission surface area in the vertical dimension rather than expanding the lateral area. The deep grooves, pits, or protrusions provide additional emission sites that are vertically integrated into the existing emitter body, allowing the emitter to maintain lower temperatures for extended lifetime while keeping the lateral footprint compact and the focusing requirements unchanged
3Duration of action of stationary object
If the emitter surface is enlarged to reduce temperature, then the lifetime is improved, but the effort to focus the electron beam increases
Solution Approach 1:
The deep structuring creates additional emission surfaces primarily in the vertical dimension through grooves, pits, or protrusions, rather than expanding the lateral emission area. This vertical integration of emission surfaces increases the effective emission capability without significantly increasing the lateral dimensions that would complicate electron beam focusing, thereby extending lifetime while maintaining manageable focusing complexity
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 approach extends the emitter's lifetime by reducing temperature while maintaining electron emission efficiency and focusing quality, achieved through structuring that maintains constant thickness and uniform temperature distribution.
Implementation Method 1
The lifetime of a thermal electron emitter in an X-ray tube (surface emitter, filament emitter) is in the first instance determined by the thermally induced evaporation of the emitter material used, generally tungsten
Implementation Method 2
heating voltage is applied to the surface emitter of the cathode, wherein heating currents from about 5 A to about 20 A flow
Implementation Method 3
the shape, length and arrangement of the lateral incisions enable special configurations of the temperature distribution to be achieved in the surface emitter since the heating of a body heated by current passage therethrough depends on the distribution of the electrical resistance across the current paths
Data Source
AI summary
An emitter has a basic unit with at least one emission surface. Accordingly, the basic unit has deep structuring in a region of the at least one emission surface. More specifically, the basic unit has the deep structuring on both a front side and on a rear side in the region of the emission surface for improving emission properties.