Three-Cone Orifice Arrangement for ICP-MS Ion Beam Control
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Solution Overview
Problem
Inductively coupled plasma mass spectrometry (ICP-MS) systems face issues with space-charge-induced matrix interferences and contamination, leading to mass discrimination, signal suppression, and contamination of ion optics, which affect analytical accuracy and require frequent maintenance.
Innovation Solution
A three-cone mass analysis system is introduced, featuring a third cone orifice with a specific angle and size configuration to reduce space charge effects and contamination, allowing a continuum flow of ions and protecting downstream optics from contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional two-cone interface is used, then the system structure is simple, but space charge effects cause mass discrimination and signal suppression
Solution Approach 1:
The interface is divided into three separate cones (sampler, skimmer, and third cone) instead of the traditional two-cone design. Each cone serves a specific function in managing the ion beam and reducing space charge effects, with the third cone specifically positioned to allow electron escape and reduce positive ion space charge density.
Solution Approach 2:
The third cone acts as an intermediary element between the skimmer and the ion optics. It provides a transition zone where electrons can escape and where the ion beam can be conditioned before entering the mass analyzer, thereby mediating the space charge problem without requiring major changes to the overall system.
2Reliability
If high bias potentials are used behind the skimmer orifice, then ion density is reduced and space charge effects are minimized, but electrical discharges occur and background equivalent concentration increases
Solution Approach 1:
Instead of applying high bias potentials across the entire region behind the skimmer, the patent uses a localized geometric solution with the third cone positioned at a specific distance (0.5-2.0 mm) from the skimmer orifice. The third cone creates a localized electric field configuration that allows electron escape without requiring high voltages, thus reducing space charge effects locally without causing electrical discharges or increasing background noise.
3Adaptability or versatility
If samples with high total dissolved solids are analyzed, then the analytical range is expanded, but contamination of ion optics occurs and maintenance frequency increases
Solution Approach 1:
The third cone extracts harmful components (electrons, neutrals, and potential contaminants) from the ion beam before it enters the sensitive ion optics region. By positioning the third cone to allow these components to escape through its orifice, the system prevents contamination of downstream components while maintaining the ability to analyze high TDS samples.
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
The system significantly improves signal intensity, especially for low-mass ions, and reduces contamination, leading to enhanced analytical precision and reduced downtime for maintenance.
Implementation Method 1
Due to their higher mobility, electrons diffuse out of the ion beam towards the inner wall of the skimmer cone as the ion beam passes through the orifice
Implementation Method 2
The formation of a negatively charged electron sheath causes the positive ions to also diffuse away from the beam axis in order of their mobility. This results in a radial expansion of the ion flux with a net charge imbalance that has a self-defocusing characteristic
Implementation Method 3
inductively coupled plasma (ICP) ionization source
Implementation Method 4
Trace elemental composition of samples is commonly determined by aspirating the sample aerosol into an ionization source such as an inductively coupled plasma (ICP) ionization source and sampling the ions
Data Source
AI summary
A mass analysis system including a sample inlet arranged to introduce a sample and an ion source coupled to the sample inlet and arranged to ionize a portion of the sample into ions. The system also includes a sampler element having a sample orifice arranged to receive the sample ions into a first vacuum chamber. The system includes a skimmer element having a skimmer orifice arranged to receive the sample ions from the first vacuum chamber into a second vacuum chamber where the skimmer orifice is of a first size. The system further includes a third cone element having a third cone orifice of a second size arranged to receive the sample ions from the second vacuum chamber into a third vacuum chamber where the third cone is configured to allow a continuum flow of ions through the third cone orifice. The third chamber includes an ion optics assembly and mass analyzer.