Electron Beam Bias Adjustment Outside the Temperature-Limited Region
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Solution Overview
Problem
Conventional methods for adjusting electron beam operating conditions in thermal electron sources often require measuring data over a wide range into the temperature limited region, leading to locally high current density distributions that can damage aperture substrates, necessitating a search for an operating point that avoids this region.
Innovation Solution
A method and apparatus that set the cathode temperature to a predetermined value, change the bias voltage while maintaining this temperature, and measure emission current within a range where a determination parameter does not exceed a threshold, thereby avoiding the temperature limited region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods measure data over a wide range into the temperature limited region to determine the operating point, then the operating point can be accurately determined, but locally high current density distribution occurs causing substrate damage
Solution Approach 1:
The invention changes the approach from varying temperature to determine the operating point to varying bias voltage while maintaining constant temperature. This parameter substitution allows accurate operating point determination without entering the harmful temperature limited region, thus avoiding substrate damage while achieving precise measurement
Solution Approach 2:
The invention introduces a determination parameter based on emission current characteristics as an intermediary indicator. By monitoring this parameter during bias voltage adjustment, the system can identify the operating point without directly measuring or entering the temperature limited region, thereby preventing substrate damage while maintaining measurement accuracy
2Use of energy by moving object
If the operating point is set near the boundary of the temperature limited region to achieve desired emission current at lowest cathode temperature, then energy efficiency is improved, but the risk of entering the temperature limited region increases causing current density non-uniformity
Solution Approach 1:
The invention implements feedback control by continuously monitoring the determination parameter (based on emission current) during bias voltage adjustment. This feedback mechanism ensures the system identifies and stops at the precise operating point boundary, maintaining optimal energy efficiency while preventing entry into the temperature limited region that would cause current density non-uniformity
Solution Approach 2:
The invention adjusts the bias voltage incrementally and stops when the determination parameter reaches a predetermined threshold, rather than continuing to the exact boundary or beyond. This partial action approach ensures the operating point is set optimally close to the boundary for energy efficiency while maintaining a safety margin to prevent current density non-uniformity
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 allows for the safe adjustment of electron beam operating conditions, preventing substrate damage by ensuring the operating point remains outside the temperature limited region, maintaining uniform current density distribution and reducing substrate damage risks.
Implementation Method 1
a thermal electron source configured to have a cathode, an anode electrode controlled to have a positive potential with respect to the cathode, and a Wehnelt electrode arranged between the cathode and the anode electrode and controlled to have a negative potential with respect to the cathode, and emit an electron beam from the cathode to the anode electrode
Data Source
AI summary
According to one aspect of the present invention, an electron beam adjustment method, includes: setting, to a predetermined value, a temperature of a cathode in a thermal electron source; changing a bias voltage applied to a Wehnelt electrode while maintaining the temperature of the cathode at the predetermined value; measuring an emission current in a case that the bias voltage is changed while maintaining the temperature of the cathode at the predetermined value; and calculating a determination parameter based on an amount of change in the emission current in a case that the bias voltage is changed, wherein each of the changing of the bias voltage, the measuring of the emission current, and the calculating of the determination parameter is repeated within a range where the determination parameter does not exceed a threshold value while maintaining the temperature of the cathode at the predetermined value.