Cathode Rejuvenation by Selective Guard Ring Ablation
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Solution Overview
Problem
Cathodes in electron beam systems, particularly those using LaB6 crystals embedded in carbon guard rings, suffer from aging issues due to evaporation and ablation, leading to reduced electron emission angles and increased electron beam spot sizes, which affect the performance of X-ray sources and other electron beam systems.
Innovation Solution
A rejuvenation method involving controlled exposure of the cathode to a specific atmosphere at elevated temperature and pressure to increase the ablation rate of the carbon guard ring relative to the LaB6 crystal, thereby counteracting the recession and restoring the electron beam divergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the cathode is heated during operation to emit electrons, then electron emission is enabled, but the crystal slowly evaporates and the end surface recedes into the carbon embedding
Solution Approach 1:
The patent applies a rejuvenation temperature and atmosphere pressure parameter combination that selectively accelerates carbon ablation while minimizing crystal loss, reversing the aging effect by changing the physical-chemical parameters of the operating environment
Solution Approach 2:
The patent converts the harmful effect of carbon ablation, which normally causes crystal recession, into a beneficial rejuvenation process by controlling the ablation rate to restore the crystal end surface to its original position
2Loss of substance
If the crystal end surface recedes into the carbon embedding, then material loss occurs, but the diameter of the end surface decreases leading to reduced electron emission angle
Solution Approach 1:
The patent performs preliminary rejuvenation treatment by applying controlled carbon ablation before the crystal recession becomes severe, preventing the deterioration of electron beam performance by restoring the crystal geometry in advance
3Reliability
If the electron beam systems use high work function material guard members, then electron emission is protected, but the guard member material ablates during operation
Solution Approach 1:
The patent changes the operating parameters by applying a specific rejuvenation temperature and atmosphere pressure that creates a selective ablation environment where the guard member ablates faster than the crystal, reversing the normal aging pattern
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 method extends the working life of the cathode by resetting the electron beam divergence, improving performance and maintaining or restoring electron beam characteristics, such as spot size and throughput.
Implementation Method 1
setting a rejuvenation temperature at the cathode
Implementation Method 2
the ablation rate of the guard member is higher than the ablation rate of the crystal
Implementation Method 3
exposing it to an atmosphere at a rejuvenation pressure
Data Source
Figure 1
Figure 2(a)~3
Figure 4a~4b
AI summary
A method for rejuvenation of a cathode in an electron-beam system is disclosed, wherein the cathode comprises an electron emitter embedded in a guard member, the method comprising: setting a pressure in an atmosphere surrounding the cathode to a rejuvenation pressure; and setting a rejuvenation temperature at the cathode; wherein, at the rejuvenation pressure and the rejuvenation temperature, an ablation rate of the guard member is higher than an ablation rate of the electron emitter. A method of operating an electron beam system involving such rejuvenation is also disclosed, as well as an associated electron impact X-ray source and a computer program that when executed causes a computer to perform the method.