Cathode Arrangement Focusing Electrode Temperature Control
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Solution Overview
Problem
Thermionic cathodes in electron guns face issues with work function lowering particles accumulating on the focusing electrode, leading to dimensional changes, charging, and distortion of the electron beam, which affects the quality and stability of the electron emission.
Innovation Solution
A cathode arrangement with a focusing electrode that maintains a temperature above a threshold to evaporate work function lowering particles at a higher rate than they arrive, preventing accumulation, and includes a heat trapping surface and adjustable heat sources to control the focusing surface temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the focusing electrode is located close to the cathode emission surface to achieve good focusing, then the focusing efficiency is improved, but work function lowering particles accumulate on the focusing electrode causing dimensional changes and charging
Solution Approach 1:
The patent applies parameter changes by heating the focusing electrode to a specific temperature range (900K to 1300K) to control the evaporation rate of work function lowering particles. This temperature parameter adjustment ensures particles evaporate at a rate equal to or higher than their arrival rate, preventing accumulation while maintaining the electrode's close positioning for effective focusing
Solution Approach 2:
The patent converts the harmful accumulation of work function lowering particles into a beneficial self-cleaning mechanism. By heating the focusing electrode to appropriate temperatures, the deposited particles naturally evaporate and are removed, transforming the problematic deposition process into a self-regulating purification system that maintains beam quality
2Reliability
If the focusing electrode is heated to evaporate work function lowering particles, then particle accumulation is prevented, but energy consumption increases
Solution Approach 1:
The patent optimizes the temperature parameter within a specific range (900K to 1300K) to achieve the minimum energy required for particle evaporation. This parameter control prevents excessive energy consumption while ensuring particles are effectively removed, balancing reliability improvement with energy efficiency
Solution Approach 2:
The focusing electrode uses its own heating capability to evaporate and remove deposited particles, creating a self-service cleaning mechanism. The system leverages the electrode's inherent thermal properties and the vapor pressure characteristics of work function lowering materials to maintain itself without requiring external cleaning systems
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 design extends the lifetime of the cathode arrangement by maintaining a stable electron emission and beam quality by preventing particle accumulation on the focusing electrode, ensuring consistent electron beam properties.
Implementation Method 1
maintains a temperature above a threshold temperature corresponding to an evaporation rate of work function lowering particles from the focusing surface that is equal to or higher than an arrival rate of work function lowering particles at the focusing surface
Implementation Method 2
an adjustable heat source configured for keeping the focusing surface of the focusing electrode at a temperature above a threshold temperature
Implementation Method 3
A thermionic cathode may be defined as a cathode heated by a heating element, for example an electrical filament, causing the cathode to release electrons with sufficient energy to overcome a work function of the material present on the emission surface
Implementation Method 4
a reservoir filled with a material that, upon heating, cause work function lowering particles to diffuse from the reservoir to the emission surface
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The invention relates to a cathode arrangement (20) comprising: a cathode body housing an emission surface (32) for emitting electrons in a longitudinal direction (Z), wherein the emission surface is bounded by an emission perimeter (35); a focusing electrode (40) at least partially enclosing the cathode body in a transversal direction and comprising an electron transmission aperture (44) for focusing the electrons emitted by the emission surface, wherein the aperture is bounded by an aperture perimeter (45), wherein the cathode body is moveably arranged within the focusing electrode over a maximum transversal distance (d1) from an aligned position (R0), and wherein the aperture perimeter transversally extends over the emission surface and beyond the emission perimeter over an overlap distance (d2) that exceeds the maximum transversal distance.