Electron Impact Ioniser with Segmented Acceleration for Soft Ionization
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Solution Overview
Problem
Current mass spectrometry techniques face challenges in achieving both soft and hard ionization efficiently, with existing methods either causing excessive fragmentation or requiring costly and complex dual systems for simultaneous soft and hard ionization, and existing ionization techniques struggle with maintaining high electron density and sensitivity at lower electron energies.
Innovation Solution
An electron impact ionization apparatus with an electron extractor and focussing element is used to generate a positive potential difference between the emitter and ionization target zone, allowing for electron deceleration and increased electron flux, enabling soft ionization without loss of sensitivity by maintaining high electron density and allowing for adjustable ionization energies between 5-30 eV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If electron energy is reduced to achieve soft ionization, then fragmentation is reduced, but ion production and sensitivity decrease sharply
Solution Approach 1:
The electron beam path is divided into two distinct acceleration zones: a first acceleration zone near the filament that generates high electron flux, and a second acceleration zone that provides controlled energy to the ionization chamber. This segmentation allows the system to maintain high electron density while delivering reduced energy to analytes, achieving soft ionization without sacrificing sensitivity.
Solution Approach 2:
A first acceleration potential (5-30V) is introduced as an intermediary between the filament and the ionization chamber. This intermediate voltage stage allows electrons to be generated at high flux near the filament while then being decelerated or maintained at low energy (5-30eV) in the ionization chamber, resolving the contradiction between electron flux and ionization energy.
2Quantity of substance
If filament current is increased to improve ion flux, then electron density increases, but Coulombic repulsion causes electron flux plateau and beam broadening
Solution Approach 1:
The acceleration process is segmented into two stages with different voltage characteristics. The first stage uses high voltage (5-30V) over a short distance to rapidly extract electrons from the filament, overcoming space charge effects. The second stage provides controlled low voltage to maintain electron energy at 5-30eV in the ionization chamber. This segmented approach allows high electron flux without the negative effects of excessive filament current.
Solution Approach 2:
The system applies a relatively high first acceleration potential (5-30V) over a very short distance to achieve rapid electron extraction, then transitions to low energy operation. This partial application of high voltage enables sufficient electron flux generation without requiring excessively high filament currents that would cause space charge limitations.
3Adaptability or versatility
If dual soft and hard ionization systems are implemented, then both ionization modes are available, but system complexity and cost increase
Solution Approach 1:
A single electron impact ionization source is designed to perform both soft and hard ionization by varying the first acceleration potential. By adjusting the voltage between 5-30V, the system can operate in soft ionization mode (producing molecular ions with minimal fragmentation) or in hard ionization mode (producing extensive fragmentation for structural information). This multi-functional design eliminates the need for separate ionization sources while maintaining both capabilities.
Solution Approach 2:
The ionization mode is made dynamic and adjustable through variable first acceleration potential. The system can switch between soft and hard ionization modes by changing the voltage setting, allowing flexible adaptation to different analytical requirements without requiring multiple fixed ionization sources.
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 enhances ionization efficiency and reduces fragmentation, allowing for both soft and hard ionization capabilities while maintaining high sensitivity and reducing the complexity and cost of the system, enabling flexible and efficient analysis of analyte molecules.
Implementation Method 1
The electrons are normally generated through thermionic emission in which an electric current is passed through a wire filament to heat the wire causing the release of energetic electrons
Implementation Method 2
A voltage supply is provided for creating a positive potential difference between the emitter and the electron extracting element such that the positive potential difference between the electron emitter and the electron extractor is greater than the positive potential difference between the electron emitter and the ionisation target zone
Implementation Method 3
the electron extracting element is configured to accelerate electrons away from the emitter along the electron pathway between the emitter and the extracting element and to decelerate the electrons along the electron pathway between the extracting element and the ionisation target zone
Implementation Method 4
A mass spectrometer operates by ionising samples in an ion source to generate charged molecules and/or molecular fragments... in which a source of gas phase neutral atoms or molecules is bombarded by electrons
Implementation Method 5
the electron focussing element is located between the emitter and the electron extracting element to focus the electrons along the electron pathway to the electron extracting element
Implementation Method 6
at large filament currents the high densities of electrons close to the filament causes Coulombic repulsion (called Space Charge Limited Emission, also known as Child-Langmuir Law in the case of planar geometry), where the repulsive forces between the high density electrons proximal to the filament itself prevent further electrons from being released
Data Source
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AI summary
An analytical apparatus (1) for mass spectrometry comprises an electron impact ioniser including an electron emitter (22) and an ionisation target zone (18). The target zone (18) is arranged to be populated with matter to be ionised for analysis. An electron extracting element (36) is aligned with an electron pathway (34) defined between the electron emitter (22) and the ionisation target zone (18). The electron extracting element (36) is configured to accelerate electrons away from the emitter (22) along the electron pathway (34) between the emitter (22) and the extracting element (36) and to decelerate the electrons along the electron pathway (34) between the extracting element (36) and the ionisation target zone (18) to enable soft ionisation while avoiding the effects of coulombic repulsion at the electron source (22).