Secondary Particle Detector Grid for Uniform Dose Distribution
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Solution Overview
Problem
Secondary particle detectors in charged particle systems suffer from non-uniform damage and contamination due to the concentrated impact of secondary particles, leading to reduced detector lifetime and maintenance costs.
Innovation Solution
A detector assembly with a grid system that creates an electric field to distribute secondary particles more evenly across the detector, using multiple sections at different potentials or a resistive grid to deflect particles away from the axis, thereby reducing maximum current density and promoting uniform distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single collection grid is used to attract secondary particles, then collection efficiency is improved, but damage and contamination become concentrated near the center of the detector, reducing detector lifetime
Solution Approach 1:
The collection grid is divided into multiple independently controlled sections (e.g., inner and outer annular regions). Each section can have its voltage independently adjusted to create a non-uniform electric field that redistributes secondary particle impact across the detector surface, preventing concentration at the center while maintaining overall collection efficiency.
Solution Approach 2:
Different regions of the collection grid are assigned different voltages to create locally optimized electric field conditions. The inner and outer regions of the detector can have tailored field strengths to achieve uniform particle distribution, with each region contributing differently to the overall collection while preventing localized damage accumulation.
2Quantity of substance
If the detector collects all secondary particles, then imaging signal strength is improved, but the maximum current density at the center causes accelerated damage and contamination
Solution Approach 1:
The voltage parameters of the collection grid sections are adjusted to change the electric field distribution. By modifying the voltage difference between inner and outer grid sections, the electric field direction and strength are altered to redirect secondary particles from the center toward the periphery, achieving uniform current density while maintaining total particle collection.
Solution Approach 2:
The collection grid voltages are made dynamically adjustable during operation. This allows the electric field configuration to be optimized in real-time based on operating conditions, enabling the system to maintain uniform particle distribution and prevent damage concentration while adapting to different secondary particle emission rates.
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 extends the useful life of secondary particle detectors by ensuring more uniform damage and contamination, reducing maintenance costs and potentially increasing imaging resolution by utilizing a larger detector area.
Implementation Method 1
A voltage applied to this grid creates an electric field between the target and grid to attract secondary particles
Implementation Method 2
A voltage applied to this grid creates an electric field between the target and grid to attract secondary particles
Data Source
AI summary
A charged particle beam system for imaging and processing targets is disclosed, comprising a charged particle column, a secondary particle detector, and a secondary particle detection grid assembly between the target and detector. In one embodiment, the grid assembly comprises a multiplicity of grids, each with a separate bias voltage, wherein the electric field between the target and the grids may be adjusted using the grid voltages to optimize the spatial distribution of secondary particles reaching the detector. Since detector lifetime is determined by the total dose accumulated at the area on the detector receiving the largest dose, detector lifetime can be increased by making the dose into the detector more spatially uniform. A single resistive grid assembly with a radial voltage gradient may replace the separate grids. A multiplicity of deflector electrodes may be located between the target and grid to enhance shaping of the electric field.