Mass Spectrometer Gas Ducting for Collision Cell Pressure Isolation
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Solution Overview
Problem
Existing mass spectrometers face issues with gas escaping from collision cells entering the vacuum chamber, which adversely affect the performance of mass filters due to ion-gas collisions, leading to reduced ion transmission and analytical performance.
Innovation Solution
The implementation of evacuation chambers and a plenum system that connect to a vacuum pump to direct escaping gases away from mass filters, using ion lenses with evacuation chambers to minimize gas entry into the vacuum chamber and maintain high vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large gaps are used between quadrupole rods to ensure gas escapes quickly from the mass filters, then gas evacuation speed is improved, but neutrals can enter the quadrupole and cause ion-gas collisions that degrade mass filter performance
Solution Approach 1:
The vacuum system is segmented into distinct pressure zones: the collision cell operates at elevated pressure while the mass filters operate at high vacuum. Physical barriers (chambers with limited apertures) separate these zones, allowing each to operate independently at its optimal pressure without compromising the other's performance
Solution Approach 2:
Limited apertures and evacuation chambers serve as intermediary structures between the collision cell and mass filters. These intermediaries control gas flow from the collision cell, preventing excessive gas from reaching the mass filters while still allowing ions to pass through for analysis
2Reliability
If high vacuum pumping is used to remove contaminants and maintain appropriate mean free path lengths, then ion beam transmission is improved, but gas load from the collision cell must be managed to prevent pressure buildup
Solution Approach 1:
Gas is extracted and removed from the collision cell region through dedicated evacuation chambers and pumping pathways. This separates the gas removal function from the ion transmission pathway, allowing high vacuum to be maintained in the mass filter region while the collision cell operates at elevated pressure for efficient ion-molecule reactions
Solution Approach 2:
The system adds a spatial dimension to gas management by creating separate vacuum zones connected through controlled apertures. Instead of attempting to evacuate all gas from a single large chamber, the system uses multiple chambers with restricted connections, effectively managing gas load through spatial separation and controlled conductance
3Productivity
If collision/reaction cell is pressurized with collision or reaction gas to generate product ions, then ion generation efficiency is improved, but escaping gas enters the vacuum chamber and adversely affects mass filter performance
Solution Approach 1:
Different regions of the instrument have different pressure qualities optimized for their specific functions: the collision cell maintains elevated pressure for efficient ion-molecule reactions, while the mass filter regions maintain high vacuum for optimal ion transmission and filtering. This local differentiation allows each component to operate at its optimal pressure without compromising overall system performance
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 maintains high pressures in collision cells while significantly reducing gas entry into mass filters, enhancing ion transmission and overall analytical performance by preventing gas-induced performance degradation.
Implementation Method 1
a vacuum pump having a pump inlet operably connected to the vacuum chamber for maintaining the vacuum chamber at an operating vacuum pressure
Implementation Method 2
a plenum fluidly connecting the evacuation chambers to the pump inlet to facilitate evacuation of collision or reaction gas escaping the collision/reaction cell to the pump inlet away from the first and second mass filters
Implementation Method 3
an entrance lens between the first mass filter and the collision/reaction cell and an exit lens between the collision/reaction cell and the second mass filter, wherein each of the entrance lens and the exit lens include a plurality of axially-spaced ion lenses and evacuation chambers between adjacent ion lenses
Data Source
AI summary
A mass spectrometer includes a vacuum chamber, a pump for maintaining a vacuum chamber at an operating vacuum pressure, an ion source, a first mass filter configured to select precursor ions, a collision/reaction cell pressurized with a collision or reaction gas and configured to generate a plurality of product ions from the precursor ions by colliding or reacting the precursor ions with one or more gas particles, and a second mass filter configured to select target ions from the product ions. Also provided are entrance and exit lenses between the collision/reaction cell and the first and second mass filters, respectively, each of which include axially-spaced ion lenses and evacuation chambers between adjacent ion lenses. A plenum fluidly connects the evacuation chambers to the pump inlet to facilitate evacuation of collision or reaction gas escaping the collision/reaction cell to the pump away from the first and second mass filters.