Plasma Mass Spectrometer Collision Chamber Design
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Solution Overview
Problem
Plasma mass spectrometers face challenges in achieving high sensitivity, particularly when analyzing high-matrix samples, as large amounts of matrix elements can contaminate the instrument and reduce analytical accuracy, and existing methods for reducing ion density often result in unintended loss of analyte ions.
Innovation Solution
A plasma mass spectrometer design featuring a small collision chamber between the interface and extraction electrode, which confines the plasma to restrict radial expansion and promote collisions between ions and electrons, selectively neutralizing argon ions and reducing plasma ion density while maintaining analyte ion numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional gas is introduced to reduce polyatomic ion interference, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a collision/reaction cell as an intermediary component between the plasma source and mass analyzer. This cell allows additional gas (mediator substance) to be introduced, enabling polyatomic ions to undergo collision or reaction processes that reduce interference. The cell acts as a mediator space where the additional gas facilitates the removal of interfering ions without requiring direct modification of the plasma source or mass analyzer, thus improving measurement precision while containing the increase in device complexity within a dedicated module.
2Measurement precision
If collision/reaction cell is added to remove interference ions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the mass spectrometer into distinct functional modules: plasma generation section, interface section, collision/reaction cell section, and mass analysis section. The collision/reaction cell is introduced as a separate, independent module with its own gas introduction system. This segmentation allows the cell to be optimized for interference removal without affecting other parts of the system, improving measurement precision while making the overall device complexity manageable through modular design.
3Quantity of substance
If plasma is confined in small collision chamber, then argon ion density is reduced, but analyte ion loss may occur
Solution Approach 1:
The patent applies local quality by creating a specific environment within the collision/reaction cell where conditions are optimized for selective neutralization of argon ions. The cell provides a localized region with controlled gas composition and pressure that promotes collisions between argon ions and neutral gas molecules, leading to selective neutralization. This localized treatment reduces argon ion density without exposing analyte ions to conditions that would cause significant loss, as the neutralization process is spatially confined and can be tuned to favor argon ion removal.
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 enhances sensitivity by reducing argon ion density and preventing ion beam spreading, allowing for effective analysis of high-matrix samples with minimal analyte ion loss and maintaining sensitivity.
Implementation Method 1
a small collision chamber which is disposed between the interface and the extraction electrode part and is defined with a side wall which extends in an axial direction as it encloses the plasma so as to restrict radial expansion of the plasma
Implementation Method 2
the expansion of the plasma in the radial direction is restricted so as to promote collisions between ions and electrons
Implementation Method 3
the ions and electrons collide with each other in the small collision chamber, whereby the argon ions are selectively neutralized
Implementation Method 4
The extraction electrodes include an electrode set at negative potential and extract the positive ions in the plasma with the electric field formed by that electrode
Implementation Method 5
By means of the ion separation part, ions are selected and separated based on their mass-to-charge ratio such that only specific ions reach the detector behind the ion separation part
Data Source
AI summary
A side wall 35 that extends in the axial direction enclosing the plasma in such a way that expansion of plasma to the sides is prevented at the back surface of a skimmer cone 33 and a small collision chamber 36, which is positioned at the back side of this side wall 35 and is defined by a flat part 56 of a first electrode 53 having an opening 57 through which the ion beam can pass. By means of this small collision chamber 36, the pressure inside the chamber rises without introducing additional gas; therefore, argon ions are neutralized by collision and recombination between the ions and electrons and the ion density of the plasma is reduced. Thus, the beam diameter during ion extraction and transport is maintained relatively small.