Segmented Voltage Control for Secondary Electron Multiplier Dynodes
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Solution Overview
Problem
Secondary electron multipliers in mass spectrometers face challenges in maintaining high ion detection efficiency over their usable period, leading to reduced sensitivity due to gradual deterioration and limitations in voltage application for ion/electron conversion and amplification gain recovery.
Innovation Solution
A secondary electron multiplier design with a first voltage applying device for the conversion dynode and a second voltage applying device for subsequent dynodes, allowing adjustable voltage application to increase ion/electron conversion yield and secondary electron emission efficiency, thereby extending the usable period and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single voltage applying device is used for all dynodes, then device complexity is reduced, but ion detection efficiency and amplification gain cannot be optimized independently
Solution Approach 1:
The voltage applying device is segmented into a first voltage applying device for the conversion dynode and a second voltage applying device for the subsequent dynodes. This segmentation allows independent voltage optimization for each dynode stage, improving ion detection efficiency and amplification gain while maintaining manageable device complexity through functional division.
2Measurement precision
If voltage is increased to recover amplification gain, then sensitivity is improved, but operational lifespan is reduced due to accelerated deterioration
Solution Approach 1:
Different voltage strategies are applied to different dynode stages. The first voltage applying device can apply higher voltage to the conversion dynode to maximize ion/electron conversion yield, while the second voltage applying device applies optimized voltage to subsequent dynodes to extend their operational lifespan. This local quality differentiation allows gain recovery without uniformly accelerating deterioration across all dynodes.
3Duration of action of stationary object
If voltage is decreased to extend usable period, then operational lifespan is extended, but ion/electron conversion yield and amplification gain are reduced
Solution Approach 1:
The voltage applying devices are designed to dynamically adjust voltages based on operational needs. The first voltage applying device can maintain higher voltage to the conversion dynode to preserve ion/electron conversion yield, while the second voltage applying device adjusts voltages to subsequent dynodes to extend their usable period. This dynamic voltage management allows the system to extend operational lifespan without sacrificing detection efficiency.
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 improves ion detection efficiency and extends the usable period of the secondary electron multiplier, leading to increased sensitivity of the mass spectrometer without significant reduction in operational lifespan.
Implementation Method 1
A secondary electron multiplier utilizes a property, which emits secondary electrons by collision of ions with a metal surface or a surface of specially-treated ceramic
Implementation Method 2
The emitted secondary electrons are accelerated by an electric field
Implementation Method 3
further subjected to repeated collisions, and thereby they are exponentially amplified
Data Source
AI summary
A secondary electron multiplier includes: a conversion dynode for emitting a secondary electron in response to an incident ion; a plurality of dynodes configured to have multi-stages from second to final stages for receiving the secondary electron; and a first voltage applying device for applying a first negative voltage to the conversion dynode and sequentially dividing the first negative voltage to apply to each of the second-stage and subsequent dynodes, wherein the secondary electron multiplier is configured to sequentially multiply the emitted secondary electron by the second-stage and subsequent dynodes. In the secondary electron multiplier, any of the second-stage and subsequent dynodes have a second voltage applying device for applying a second negative voltage. The secondary electron multiplier has an improved ion detection efficiency without a large reduction of a usable period thereof, thereby enhancing the sensitivity of a mass spectrometer.