Compact Modular Cathode With Gas-Impermeable Membrane
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Solution Overview
Problem
Field emitter arrays in cathodes face challenges due to sensitivity to emitter tip radii spread and fluctuation of work function caused by gas adsorption and desorption, leading to spatial and temporal non-uniformity, as well as tip damage from Joule heating.
Innovation Solution
A compact modular cathode unit is developed with a membrane window that is selectively transmissive to electrons but impermeable to gas molecules, combined with a modular housing unit that is impermeable to oxidizing gases, to reduce degradation and enhance stability and control of electron emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field emitter arrays are used in demanding device applications, then electron emission capability is achieved, but reliability deteriorates due to sensitivity to emitter tip radii spread and work function fluctuation
Solution Approach 1:
The cathode is divided into multiple modular units, each containing a controlled number of field emitter elements. This segmentation allows for localized replacement and maintenance of individual modules without affecting the entire cathode array, thereby improving reliability while managing the inherent non-uniformity of field emitter tips.
Solution Approach 2:
The patent employs a vacuum environment with controlled atmosphere to minimize gas adsorption and desorption at the emitter tip surfaces. This inert environment stabilizes the work function and reduces temporal non-uniformity, thereby improving reliability without requiring perfect uniformity in emitter tip radii.
2Productivity
If field emitter elements operate at high current density, then electron beam performance is improved, but tip damage occurs due to Joule heating from micro-plasma explosion
Solution Approach 1:
The patent employs dynamic control of the electron emission process by individually addressing field emitter elements in arrays. This allows for real-time monitoring and adjustment of current density at each emitter, enabling high overall productivity while preventing localized overheating and tip damage through adaptive current management.
Solution Approach 2:
The patent changes operational parameters by controlling the potential difference applied to each field emitter element independently. By dynamically adjusting these parameters, the system can operate at high current densities when needed while preventing conditions that lead to micro-plasma explosions and tip damage, thus maintaining tip integrity.
3Reliability
If modular cathode units are used to improve reliability, then device complexity increases due to additional membrane windows and housing structures
Solution Approach 1:
The membrane window in the modular cathode design serves multiple functions: it provides mechanical support for the vacuum seal, acts as a barrier to gas molecules, and allows for electron transmission. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while maintaining improved reliability.
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 achieves high current density and long lifetime, allowing for reliable operation in poor vacuum environments and enabling the use of field emitter arrays in demanding applications with improved spatial and temporal control of electron emissions.
Implementation Method 1
At least one gate electrode is disposed proximate to the second end of the at least one field emitter element, to apply a potential difference proximate to the field emitter tip of the at least one field emitter elements, thereby extracting electrons (via tunneling) from the at least one field emitter tip to form an electron beam
Implementation Method 2
The membrane window is formed of a material that is selectively transmissive to electrons but impermeable to gas molecules
Implementation Method 3
at least one anode component that is configured to accelerate the electron beam in a path directed at the membrane window of the modular housing unit
Data Source
AI summary
Example compact modular electron beam units are provided that can be used to generate electron beams using field emitter elements. A modular electron beam unit may comprise an electron beam source including a base portion, at least one field emitter element coupled to the base portion, the field emitter element including a field emitter tip, at least one gate electrode and a membrane window disposed over the at least one gate electrode.