Linear Ion Trap Radial Amplitude Assisted Transfer
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Solution Overview
Problem
Mass selective axial ejection in linear ion guides of mass spectrometers faces inefficiencies due to high radial energy ions being lost at apertures and extensive fragmentation when exposed to high fringing fields, leading to compromised ejection efficiency and ion loss.
Innovation Solution
A mass spectrometer with a linear ion trap employing radial amplitude assisted transfer (RAAT) technology, where ions are radially excited using an AC field and further accelerated by a pseudo-potential generated by a reduction in RF field strength, allowing radially excited ions to overcome a DC potential barrier while unexcited ions remain trapped, utilizing a combination of axial and pseudo-potential forces to enhance ion ejection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high radial excitation amplitude is applied to eject ions axially, then ejection efficiency is improved, but ion loss at apertures and fragmentation increase
Solution Approach 1:
The ion ejection process is segmented into two distinct phases: first, radial excitation is applied to specific ion populations to increase their radial amplitude; second, a reduced RF field strength creates a pseudo-potential that selectively accelerates only the radially excited ions axially. This segmentation allows efficient ejection of target ions while leaving unexcited ions trapped, preventing ion loss at apertures and reducing fragmentation.
Solution Approach 2:
The invention transitions from traditional axial ejection methods to a two-dimensional approach: radial excitation is applied in the radial dimension to select ions, while axial acceleration is achieved through pseudo-potential in the axial dimension. This dimensional separation enables selective ejection based on radial amplitude while controlling axial transport, improving ejection efficiency without increasing ion loss.
2Speed
If high fringing fields are used to accelerate ions axially, then ion transfer is enhanced, but extensive fragmentation occurs
Solution Approach 1:
The RF field strength parameter is dynamically changed by reducing it in the ejection region compared to the trapping region. This parameter change creates a pseudo-potential that provides axial acceleration force to radially excited ions without requiring high fringing fields, thereby enhancing ion transfer speed while minimizing fragmentation.
3Measurement precision
If DC potential barrier is applied to prevent unexcited ions from exiting, then ion selectivity is improved, but voltage tolerance requirements increase
Solution Approach 1:
The pseudo-potential created by reduced RF field strength acts as an intermediary mechanism that provides selective axial acceleration to radially excited ions. This intermediary force works in conjunction with the DC potential barrier, allowing the barrier to be set at lower voltages while maintaining ion selectivity, thereby reducing voltage tolerance requirements.
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 improves ion extraction efficiency and relaxes voltage tolerances, allowing radially excited ions to exit while maintaining unexcited ions within the trap, thereby enhancing the overall performance of mass selective axial ejection.
Implementation Method 1
Ions are trapped radially by an RF (radio-frequency) quadrupole field
Implementation Method 2
axially by static DC (direct current) potentials applied at the ends of the ion guide
Implementation Method 3
An axial force arises due to a pseudo-potential that develops axially at the fringe region of the ion guide, that is dependent on the amplitude of radial excitation
Data Source
AI summary
Systems, methods and apparatus for radial amplitude assisted transfer (RAAT) in mass spectrometers are provided in which ions for RAAT are accelerated along a longitudinal axis of a mass spectrometer in order to decrease the magnitude of excitation energy of radially excited ions in an ion trap that allows the radially excited ions to exit the ion trap. Hence, the radially excited ions exit the ion trap with reduced radial energy thereby decreasing the exit angle of the radially exited ions from the ion trap. Furthermore, combined forces on the ions are such that radially excited ions exit the ion trap while unexcited ions remain in the ion trap.