De Laval Nozzle Vacuum Interface for Mass Spectrometer Ion Transmission
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Solution Overview
Problem
Current vacuum interfaces for mass spectrometers face challenges in efficiently transferring ions from atmospheric pressure to a vacuum chamber while maintaining effective vacuum conditions and preventing clogging, especially when dealing with less volatile molecules with higher boiling points.
Innovation Solution
A de Laval nozzle with a converging-diverging geometry is used as an interface to accelerate ions, combined with a two-stage or multi-stage system to manage pressure differences and prevent clogging, and an ion guide to focus and enrich the ion beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a small orifice is used in the vacuum interface, then the vacuum quality is maintained, but the ion transmission efficiency decreases and clogging risk increases
Solution Approach 1:
The vacuum interface is divided into multiple stages with progressively smaller orifices (first orifice larger than second orifice), allowing each stage to handle different flow rates. This segmentation enables the system to maintain vacuum quality in the mass spectrometer while providing a larger effective opening for ion transmission, reducing clogging risk without compromising vacuum integrity.
2Productivity
If a larger orifice is used in the vacuum interface, then the risk of clogging is reduced, but the vacuum quality deteriorates
Solution Approach 1:
The interface uses a multi-stage orifice arrangement where larger orifices are positioned upstream and progressively smaller orifices downstream. This allows the system to present a large effective opening to the ion source (reducing clogging) while the final downstream orifice maintains the required vacuum quality for the mass spectrometer.
Solution Approach 2:
Different regions of the vacuum interface have different orifice sizes optimized for their specific functions: larger orifices in regions handling high flow rates from the ion source, and smaller orifices in regions requiring vacuum maintenance. This local optimization allows simultaneous achievement of high ion transmission and vacuum quality.
3Device complexity
If a simple orifice is used for vacuum interface, then the device complexity is low, but the ion acceleration and focusing capability is insufficient
Solution Approach 1:
The vacuum interface incorporates electrodynamic elements (RF quadrupole ion guide, DC electrodes) that create dynamic electric fields to accelerate and focus ions. These dynamic fields provide ion acceleration and focusing capabilities far beyond what a simple passive orifice could achieve, while the orifice structure itself remains relatively simple.
Solution Approach 2:
The system introduces an RF quadrupole ion guide as an intermediary component between the vacuum interface and the mass analyzer. This intermediary element provides strong ion focusing and transmission capabilities without requiring complex modification of the vacuum interface orifices themselves.
4Productivity
If multiple stages are used in the vacuum interface, then the vacuum quality and ion transmission are improved, but the device complexity increases
Solution Approach 1:
The multi-stage interface is segmented into distinct functional zones (first chamber with first orifice, second chamber with second orifice, RF quadrupole region). Each segment performs a specific function (ion introduction, vacuum maintenance, ion guiding), allowing the system to achieve high ion flux while keeping each individual component relatively simple and well-understood.
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 configuration significantly improves the useful ion flux and maintains vacuum conditions by accelerating ions to supersonic velocities and focusing them for efficient analysis, while also allowing for larger orifices to reduce clogging risks.
Implementation Method 1
A de Laval nozzle with a converging-diverging geometry is used as an interface to accelerate ions
Implementation Method 2
an ion guide to focus and enrich the ion beam
Data Source
AI summary
This invention describes a vacuum interface for a mass spectrometer system formed from a diverging nozzle. The vacuum interface may be used to transfer a beam of ions from an atmospheric pressure ionization source into a vacuum chamber for analysis by a mass analyser.