FTMS Measuring Cell RF Grid Ion Confinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ion cyclotron resonance mass spectrometers face challenges with magnetron circular motion causing frequency shifts and reduced usable volume, as well as limitations in mass accuracy due to space charge and vacuum issues, particularly for high specific ion masses.
Innovation Solution
The measuring cell employs fine structural elements for trapping electrodes connected to RF voltage, generating repelling pseudopotentials that prevent magnetron motion and allow for a fine ion string formation, increasing mass resolution and accuracy by bringing the ion string closer to detection electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional trapping electrodes with DC voltage are used, then ions can be confined in the measuring cell, but magnetron circular motion occurs causing frequency shifts and reduced usable volume
Solution Approach 1:
The patent changes the parameter of trapping electrode voltage from DC to RF voltage. This parameter change fundamentally alters the interaction between the trapping field and ions, eliminating magnetron motion while maintaining ion confinement. The RF voltage creates a time-averaged potential that confines ions without generating the static electric field components that cause magnetron circular motion.
Solution Approach 2:
The patent employs fine structural elements (wire grid) for the trapping electrodes, creating localized RF fields between the wires. This local quality approach generates repelling pseudopotentials in specific regions that prevent magnetron motion while allowing ions to be confined in the central region where measurements occur.
2Quantity of substance
If ions are confined using conventional electrodes, then the measuring cell can operate, but space charge effects limit the scanning capacity before cyclotron frequency is affected
Solution Approach 1:
By changing from DC to RF trapping voltage, the patent creates a different potential landscape that reduces space charge effects. The time-varying RF field prevents ions from accumulating in a way that would create significant space charge, thereby maintaining cyclotron frequency accuracy even with larger ion populations.
3Volume of stationary object
If the measuring cell volume is increased to improve ion statistics, then more ions can be measured, but magnetron motion increases causing greater frequency shifts
Solution Approach 1:
The RF trapping mechanism allows for larger measuring cell volumes without proportionally increasing magnetron motion effects. The time-averaged nature of the RF potential and the fine wire grid structure create confinement that scales differently with volume compared to DC trapping, enabling larger cells to be used while maintaining measurement precision.
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 design enables higher mass resolution and accuracy with reduced magnetron motion, longer ion string preservation, and improved scanning capacity before space charge affects the cyclotron frequency, allowing for more precise mass determination.
Implementation Method 1
fine structural elements for trapping electrodes connected to RF voltage, generating repelling pseudopotentials that prevent magnetron motion
Implementation Method 2
the mass-to-charge ratios m/z of ions are measured by their cyclotron movements in a homogeneous magnetic field with high field strength
Implementation Method 3
The magnetic field is usually generated by superconductive magnetic coils cooled in liquid helium
Data Source
AI summary
The invention relates to a measuring cell for an ion cyclotron resonance mass spectrometer (FTMS). The invention provides a measuring cell which, on the one hand, consists of two ion-repelling RF grids at the front ends as trapping electrodes and thus produces a pure cyclotron motion of the ions without the usually co-existing magnetron motion and, on the other hand, measures a multiplied cyclotron frequency by means of a plurality of detection electrodes, whereby either a higher mass accuracy or a shorter measuring time can be achieved.