Particle Beam Objective Lens Coil Current Control
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Solution Overview
Problem
Existing particle beam apparatuses face challenges in accurately controlling the current for objective lens coils due to noise and temperature-related inaccuracies, leading to fluctuations in particle beam focusing.
Innovation Solution
The apparatus employs a circuit arrangement that controls the sum or difference of coil currents, using a summation-difference unit to stabilize the magnetic flux and reduce noise, with thermally coupled measuring resistors to maintain constant temperatures and high resistance values for improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate current control units with individual measuring resistors are used for each coil, then independent control of each coil current is achieved, but noise and temperature-related inaccuracies increase leading to beam focusing fluctuations
Solution Approach 1:
The patent combines the control of first and second coil currents into a single integrated current control unit. This unit uses a single measuring resistor to measure the total current, which is then distributed to both coils. By merging the control functions and using a common measuring resistor that is thermally coupled to both coils, the system reduces noise and temperature-related inaccuracies while maintaining the ability to independently control each coil's current through internal distribution circuitry.
2Measurement precision
If high resistance measuring resistors are used to improve signal-to-noise ratio, then measurement precision improves, but temperature stability becomes more difficult to maintain
Solution Approach 1:
The patent applies local quality by thermally coupling the single measuring resistor to both coils in a controlled manner. The measuring resistor is positioned in thermal contact with the coils, allowing it to track their temperature changes locally. This localized thermal coupling ensures that the measuring resistor experiences the same temperature variations as the coils, compensating for temperature-related resistance changes and maintaining measurement precision without requiring excessive resistance values.
3Adaptability or versatility
If multiple separate current control circuits are implemented, then individual coil control capability is maintained, but circuit complexity and noise levels increase
Solution Approach 1:
The patent implements a universal current control unit that serves multiple functions: it measures the total current through a single measuring resistor, distributes the current to both coils, and provides independent control capability for each coil through internal circuitry. This multi-functional design eliminates the need for separate control circuits for each coil, reducing overall circuit complexity and noise levels while maintaining the versatility to adjust each coil's current independently.
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 results in stable control of the particle beam focusing, minimizing noise influence and maintaining accurate beam deflection with lower noise levels compared to prior art.
Implementation Method 1
thermally coupled measuring resistors to maintain constant temperatures and high resistance values for improved signal-to-noise ratio
Implementation Method 2
controls the sum or difference of coil currents, using a summation-difference unit to stabilize the magnetic flux and reduce noise
Data Source
AI summary
The system described herein relates to a particle beam apparatus for analyzing and/or for processing an object and to a method for operating a particle beam apparatus. The particle beam apparatus is designed for example as an electron beam apparatus and/or an ion beam apparatus. The particle beam apparatus comprises a beam deflection device, for example an objective lens, which is provided with a first coil and a second coil. The first coil is operated with a first coil current. The second coil is operated with a second coil current. The first coil current and/or the second coil current may always be controlled in such a way that the sum of the first coil current and the second coil current (the summation current) or the difference between the first coil current and the second coil current (the difference current) is controlled to a setpoint value.