Skimmer Cone Plasma Separation for Mass Spectrometer Memory Effects
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Solution Overview
Problem
The throughput of ICP-MS instruments is reduced due to material deposition on the skimmer cone and sampling cone surfaces, leading to memory effects that affect analysis, particularly in instruments with enclosed or elongated skimmer cones.
Innovation Solution
A skimmer apparatus with a plasma-separation means on its internal surface separates a portion of the skimmed plasma adjacent to the surface from the remainder, allowing the latter to expand towards ion extraction optics while preventing deposition ions from interfering, using an adsorbent or getter material to trap and remove deposited matter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the skimmer cone is enclosed or elongated to improve ion extraction efficiency, then ion beam quality is improved, but material deposition on the skimmer cone surface increases leading to memory effects
Solution Approach 1:
The skimmer cone internal surface is segmented into distinct functional zones: a deposition zone where material is allowed to accumulate, and a plasma expansion zone that remains clean. This segmentation is achieved through controlled plasma flow paths and vacuum pumping arrangements that confine deposited material to specific regions away from the ion extraction path.
Solution Approach 2:
Deposited material is selectively removed from the plasma expansion region through targeted vacuum pumping or thermal desorption techniques. The deposition zone is equipped with separate pumping channels that extract accumulated material without affecting the clean plasma expansion zone, thereby eliminating memory effects while preserving ion extraction efficiency.
2Quantity of substance
If the skimmer cone aperture is reduced to improve ion focusing, then ion beam concentration is improved, but material deposition rate on the cone surface increases
Solution Approach 1:
Different regions of the skimmer cone are assigned different functional qualities: the aperture region is optimized for ion focusing with small dimensions, while the internal surface regions are designed to either collect or reject deposited material. The local geometry and surface properties are tailored to each zone's specific function, allowing the aperture to remain small for better focusing while deposition is managed in other regions.
Solution Approach 2:
The problem of material deposition is moved from the ion extraction dimension to a separate deposition collection dimension. By creating dedicated deposition zones with different geometric configurations and pumping arrangements, the system handles material accumulation in a dimension separate from the ion beam path, allowing small aperture sizes without proportionally increased deposition interference.
3Measurement precision
If the plasma expansion region is increased to improve ion separation, then ion beam quality is improved, but the volume available for plasma expansion increases leading to more material deposition
Solution Approach 1:
The plasma expansion region is designed with asymmetric geometry that provides sufficient volume for ion separation in the critical directions while minimizing surface area available for material deposition. The expansion chamber shape is optimized to concentrate plasma volume where ion separation occurs, while reducing peripheral surfaces where deposition would accumulate and cause memory effects.
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 solution significantly reduces memory effects by minimizing the interaction of deposition ions with the plasma expansion, thereby improving instrument throughput and reducing contamination risks, allowing for more efficient and accurate analysis.
Implementation Method 1
using an adsorbent or getter material to trap and remove deposited matter
Data Source
AI summary
A mass spectrometer vacuum interface can include a skimmer apparatus having a skimmer aperture and an internal surface. A method of operating the mass spectrometer vacuum interface can include establishing an outwardly directed flow along the internal surface of the skimmer apparatus.