Ion Source Filter with Reduced r/r0 Ratio for High-Pressure Mass Spectrometry
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Solution Overview
Problem
Brighter ion sources in mass spectrometers lead to increased contamination of components, requiring frequent cleaning and downtime due to fouling, which is exacerbated by high vacuum pressures and limited ion filtering capabilities.
Innovation Solution
A source filter with a reduced r/r0 ratio of rod electrode cross-sectional radius to inscribed circle radius, operated at high pressures, improves ion filtering performance by reducing the negative impact of pressure on filtering efficiency and introducing even-order multipole potentials to enhance ion beam confinement and transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If brighter ion sources are used to increase ion delivery, then instrument sensitivity is improved, but component contamination increases requiring frequent cleaning
Solution Approach 1:
The source filter performs preliminary filtering of unwanted ions before they reach downstream components. By rejecting contaminating ions at the source region, the filter prevents contamination before it occurs, allowing brighter ion sources to be used without the usual penalty of frequent cleaning.
Solution Approach 2:
The source filter acts as an intermediary component between the ion source and downstream mass spectrometer components. It selectively transmits desired ions while blocking unwanted ions, serving as a protective barrier that allows high-intensity ion beams to be used without damaging downstream components.
2Object-affected harmful factors
If conventional quadrupole mass filters are used for ion filtering, then unwanted ions are rejected, but performance degrades at high vacuum pressures
Solution Approach 1:
The source filter uses modified geometric parameters (rod radius to inscribed circle ratio r/r0 < 0.8) and operating parameters (RF voltage, DC voltage) optimized for high-pressure operation. These parameter changes enable the filter to maintain stable ion transmission and effective mass filtering even at vacuum pressures where conventional filters fail.
Solution Approach 2:
The source filter employs non-ideal rod geometry with specific r/r0 ratios that create localized field characteristics suitable for high-pressure operation. This local optimization of the electric field structure allows the filter to compensate for pressure-induced performance degradation.
3Ease of manufacture
If standard r/r0 ratio rod electrodes are used, then manufacturing is simplified, but filtering performance suffers at high pressures due to increased voltage breakdown risks
Solution Approach 1:
By reducing the r/r0 ratio below 0.8, the electric field distribution is modified to reduce peak field intensities that cause voltage breakdown. This parameter change maintains manufacturing simplicity while significantly improving reliability at high pressures by preventing discharge between rods.
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 source filter achieves improved ion filtering performance and reduced contamination by maintaining high efficiency at higher pressures, with resolution and performance benefits of 20-50% compared to standard designs, and allows for effective rejection of unwanted ions while minimizing ion-ion interactions and voltage breakdown risks.
Implementation Method 1
a voltage source is configured to apply oscillatory (i.e., radio-frequency (RF)) and resolving DC voltages to the rod electrodes
Implementation Method 2
m/z-selective transmission of ions
Implementation Method 3
introducing even-order multipole potentials to enhance ion beam confinement and transmission
Data Source
AI summary
An ion source filter for use in the source region is disclosed. The ion source filter includes four rod electrodes having circular cross sections. The rod electrodes of the ion source filter are sized and positioned such that the ratio r/r0 of the rod radius to the inscribed circle radius is considerably reduced relative to conventional RF/DC mass filters. The reduced r/r0 geometry has been observed to lessen the diminishment of resolution with increasing pressure relative to prior art devices.