Ion Detector with Offset Angled Detection Channels
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Solution Overview
Problem
Existing ion detectors face challenges in efficiently detecting both positive and negative ions simultaneously due to complex and costly switching hardware, delayed switching, and inadequate prevention of neutral particles, which lead to signal noise and reduced sensitivity.
Innovation Solution
An ion detector system comprising an ion guide with offset and angled positive and negative ion detection devices, each biased with appropriate voltages to direct ions along orthogonal paths, eliminating the need for conversion dynodes and allowing simultaneous or sequential detection of both polarities without neutral particle interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single ion detector is configured to detect both positive and negative ions by switching voltage polarity, then the detector can detect both ion polarities, but the switching hardware becomes complex and costly, and the switching speed is limited
Solution Approach 1:
The ion detector is divided into two separate detection channels: one for positive ions and one for negative ions. Each channel has its own ion-to-electron conversion surface optimized for its specific ion polarity, eliminating the need for voltage polarity switching while maintaining the ability to detect both ion types simultaneously or sequentially
Solution Approach 2:
A conversion dynode is introduced as an intermediary component that converts negative ions to positive ions (or vice versa) before they reach the ion-to-electron conversion surface. This allows a single ion detector to handle both ion polarities without requiring complex voltage switching hardware
2Adaptability or versatility
If the entrance into the signal multiplier is aligned on-axis with the incoming ion beam to detect both polarities, then the detector can accept ions of both polarities, but neutral particles also enter and cause signal noise and reduced sensitivity
Solution Approach 1:
The ion-to-electron conversion surfaces are positioned at specific angular orientations relative to the ion beam axis. The positive ion detection surface is oriented to preferentially accept positive ions, while the negative ion detection surface is oriented to preferentially accept negative ions. This angular differentiation creates local quality differences that selectively guide ions of appropriate polarity to their respective conversion surfaces while excluding neutral particles
Solution Approach 2:
The conversion dynode, which could potentially convert unwanted neutral particles, is instead used to convert negative ions to positive ions (or vice versa) in a controlled manner. This converts the potential harm of neutral particle interference into a benefit by ensuring that only charged ions reach the detection surfaces, as neutral particles do not respond to the electric fields and thus cannot reach the conversion surfaces
3Adaptability or versatility
If voltage polarity switching is implemented to detect different ion polarities, then the detector can be versatile, but the switching requires large voltage swings that limit maximum switching speed and require complex fast-switching circuitry
Solution Approach 1:
The detector employs dynamic voltage assignment where the voltage polarity on each detection channel is independently controllable. Rather than switching the entire detector between positive and negative modes, each channel maintains its optimal voltage polarity dynamically, allowing rapid switching between detection modes without the inertia of large voltage swings across the entire system
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 configuration simplifies the detector design, reduces noise, enhances sensitivity, and enables efficient detection of both positive and negative ions, while minimizing the complexity and cost of switching circuitry and preventing neutral particle interference.
Implementation Method 1
The ion guide includes a plurality of electrodes arranged about a first axis and configured to apply an RF field to constrain ions to motions generally about the first axis
Implementation Method 2
The positive ion detection device is configured to apply a negative voltage bias and accelerate positive ions along a positive ion path directed from the ion guide into the positive ion inlet
Implementation Method 3
The negative ion detection device is configured to apply a positive voltage bias and accelerate negative ions along a negative ion path directed from the ion guide into the negative ion inlet
Implementation Method 4
The ion-to-electron conversion stage typically includes a surface that emits electrons in response to impingement by ions
Implementation Method 5
The electrical current resulting from the ion-to-electron conversion is amplified in the multiplier stage through multiplication of liberated electrons
Data Source
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Figure 3~4
AI summary
An ion detector comprises an ion guide with electrodes arranged about a first axis; a positive ion detection device with an ion inlet at a first side of the ion output section offset from and at an angle to the first axis; and a negative ion detection device with an ion inlet at a second side opposite the first side, offset from and at an angle to the first axis. A negative voltage bias applied to the positive ion device accelerates positive ions toward the inlet along a path including a component along a second axis orthogonal to the first axis. A positive voltage bias applied to the negative ion detection device accelerates negative ions toward the inlet along a path that includes a component along the second axis orthogonal to the first axis in a direction generally opposite to the path of the positive ions.