Phase-Locked Linear Ion Trap for Consistent Fourier Mass Detection
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Solution Overview
Problem
Existing Fourier transform mass spectrometers face challenges with variable ion ejection times and loss of micromotion information due to radial to axial motion conversion in linear ion traps, leading to lower signal intensity and information loss.
Innovation Solution
A mass analyzer with a phase-locked quadrupole system where the RF confinement voltage, excitation signal, and data acquisition trigger are synchronized, ensuring consistent ion ejection and preserving micromotion information by converting radial oscillations into axial oscillations for improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass selective axial ejection is used to eject ions from the linear ion trap, then ion detection can be achieved, but the ejection time varies from scan to scan leading to lower average signal intensity
Solution Approach 1:
The patent applies periodic action by using phase-locked RF confinement voltage and excitation signals that operate at specific secular frequencies. The RF voltage is applied periodically to confine ions radially, and excitation signals are applied at secular frequencies to induce radial oscillations at predictable intervals, ensuring consistent ion ejection timing across scans and improving average signal intensity.
Solution Approach 2:
The patent implements feedback through phase-locking the RF confinement voltage and excitation signals to maintain consistent phase relationships. The system monitors and adjusts the phase of the RF voltage to ensure that ion ejection occurs at the optimal phase angle, thereby maintaining consistent ejection timing and maximizing signal intensity across multiple scans.
2Ease of operation
If radial excitation is used to convert radial oscillations into axial oscillations via fringing fields, then ion ejection can be achieved, but information regarding micromotion of the ions is lost
Solution Approach 1:
The patent applies preliminary action by carefully controlling and phase-locking the excitation signal to be applied at the correct phase relative to the RF confinement voltage. This ensures that radial excitation is applied at the optimal moment in the ion trajectory, enabling efficient conversion to axial oscillations while preserving micromotion information through synchronized detection.
Solution Approach 2:
The patent replaces direct mechanical measurement of ion micromotion with an electromagnetic field-based detection system. By using phase-locked RF and excitation signals, the system indirectly measures ion motion through the phase and amplitude of the detected signal, preserving micromotion information without requiring direct mechanical intervention that would disrupt the ions.
3Measurement precision
If phase locking is implemented to synchronize RF confinement voltage, excitation signal and data acquisition trigger, then signal-to-noise ratio is enhanced, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the phase-locking system by simultaneously controlling the RF confinement voltage, excitation signal, and data acquisition trigger with a single phase-reference mechanism. This unified approach synchronizes all three signals to the same phase angle, enhancing signal-to-noise ratio while minimizing the additional complexity that would result from separate synchronization systems.
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 approach enhances the signal-to-noise ratio of mass detection signals and preserves micromotion information, resulting in more consistent and accurate mass spectra across multiple scans.
Implementation Method 1
an RF voltage can be applied to at least one of the rods for generating a quadrupolar field for causing radial confinement of the ions as they propagate through the quadrupole
Implementation Method 2
the radially-excited ions interact with fringing fields at the vicinity of the output end as they exit the trap such that their radial oscillations are converted into axial oscillations
Data Source
AI summary
In one aspect, a mass analyzer is disclosed, which comprises a quadrupole having an input end for receiving ions and an output end through which ions can exit the quadrupole, said quadrupole having a plurality of rods to at least some of which a drive RF signal and an excitation signal can be applied. A fixed phase relationship is maintained between the drive RF signal and the excitation signal, thereby enhancing the signal-to-noise ratio of the mass detection signal.