Dynamic Electron Impact Ion Source with Electric Field Compensation
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Solution Overview
Problem
In GC/MS instruments, the magnetic field used to enhance ionization efficiency in the ion source can cause ionized sample constituents to deviate from their path, leading to a non-uniform or scattered exit, which negatively impacts the performance of the mass analyzer by causing collisions with chamber walls and reduced transmission efficiency.
Innovation Solution
An electric field generator is used within the ion source chamber to compensate for the magnetic field's effect on ionized sample constituents, applying a force opposite and equal in magnitude to the magnetic field's force, ensuring a more focused and straight path for the ions to exit the ion source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a magnetic field is used to enhance ionization efficiency, then the ionization efficiency is improved, but the ionized sample constituents deviate from their path and exit in a scattered manner
Solution Approach 1:
An electric field is introduced as an intermediary force to counterbalance the harmful lateral force exerted by the magnetic field on ionized constituents. The electric field acts as a mediator that allows the magnetic field to remain for ionization enhancement while preventing the scattering effect, thereby resolving the contradiction between ionization efficiency and ion beam focus.
2Productivity
If a magnetic field is applied to lengthen electron path, then electron-ion interaction increases, but ionized constituents collide with chamber walls
Solution Approach 1:
The electric field serves as a counterbalancing force that opposes the lateral deflection caused by the magnetic field. By applying an equal and opposite electric force, the system counterweights the harmful effect of magnetic field-induced ion trajectory deviation, preventing wall collisions while maintaining the beneficial electron path lengthening effect.
3Device complexity
If no electric field compensation is applied, then device complexity is low, but mass analyzer performance deteriorates
Solution Approach 1:
The system changes the physical parameters within the ion source by superimposing an electric field onto the existing magnetic field configuration. This parameter change allows the magnetic field to maintain its ionization-enhancing function while the electric field parameter compensates for the harmful lateral forces, thereby improving mass analyzer performance without requiring fundamental structural redesign.
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 compensation results in improved focusing and acceleration of ions, enhancing the transmission efficiency and resolving power of the mass analyzer by maintaining a finely focused beam with reduced angular spread, thereby improving the overall performance of the GC/MS system.
Implementation Method 1
the magnetic field can impart a Lorentz force on the ionized sample constituents in a direction orthogonal to their direction of travel
Implementation Method 2
the electric field generator can be configured to generate an electric field within the ion source chamber, such that an additional force is imparted on the ionized sample constituents
Implementation Method 3
generate ions in an ionization region within the ion source chamber through an interaction between the gas-phase neutral species and the electron
Data Source
AI summary
An ion source can include a magnetic field generator configured to generate a magnetic field in a direction parallel to a direction of the electron beam and coincident with the electron beam. However, this magnetic field can also influence the path of ionized sample constituents as they pass through and exit the ion source. An ion source can include an electric field generator to compensate for this effect. As an example, the electric field generator can be configured to generate an electric field within the ion source chamber, such that an additional force is imparted on the ionized sample constituents, opposite in direction and substantially equal in magnitude to the force imparted on the ionized sample constituents by the magnetic field.