Electron Beam Current Density Control for Uniform Incident Dose
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Solution Overview
Problem
Conventional electron beam adjustment methods fail to ensure a desired incident dose is achieved uniformly across all regions of the target object due to variations in current density distribution, particularly at the outer peripheries.
Innovation Solution
Measure the current density distribution of the electron beam and adjust the cathode temperature based on feature amounts outside a threshold range to ensure uniform current density across the target object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cathode temperature is increased to improve the current density of the entire electron beam, then the emission current increases, but the current density distribution becomes non-uniform across the target object
Solution Approach 1:
The patent divides the electron beam into multiple regions and measures current density at each region separately. By identifying regions with insufficient current density (outer peripheral regions) and selectively increasing cathode temperature only when needed, the system achieves uniform current density distribution across all regions without creating non-uniformity through blanket temperature increases.
Solution Approach 2:
The patent implements a feedback control system where current density is measured at multiple regions, compared against reference values, and used to control cathode temperature adjustments. This feedback mechanism ensures that temperature increases are applied only when and where needed to maintain uniform current density distribution, preventing the non-uniformity problem that occurs with conventional methods.
2Quantity of substance
If the emission current is increased to maintain current density, then the total beam intensity improves, but the current density distribution uniformity deteriorates
Solution Approach 1:
The patent measures current density at multiple discrete regions across the target object and identifies specific regions where current density is insufficient. By applying temperature control based on regional measurements rather than uniform adjustments, the system maintains emission current while preserving current density distribution uniformity across different regions of the target object.
Solution Approach 2:
The patent performs preliminary measurement of current density distribution across multiple regions before adjusting emission current or cathode temperature. This preliminary assessment allows the system to determine the appropriate emission current level that will maintain uniform current density distribution, preventing the uniformity deterioration that occurs when emission current is increased without prior regional assessment.
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
Ensures a consistent incident dose is achieved across the entire target object by optimizing the cathode temperature to match the current density distribution, addressing non-uniformity issues.
Implementation Method 1
adjustment is made such that the current density of the entire electron beam is periodically measured, and when the density is insufficient, the emission current is increased. If still insufficient, a cathode temperature is increased
Data Source
AI summary
An electron beam adjustment method includes measuring a current density distribution of an electron beam to reach a target object, calculating a feature amount of a measured current density distribution, and increasing, in the case of the feature amount being outside the range of a threshold, a temperature of an electron beam emission source.