Linear Ion Trap With Oscillating On-Axis Potential
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Solution Overview
Problem
Conventional linear ion traps face limitations in efficiently extracting and scanning ions for mass analysis due to radial and axial ejection mechanisms, which affect the accuracy and speed of mass spectrometry.
Innovation Solution
A linear ion trap design incorporating an oscillating on-axis potential with a non-zero second derivative, combined with DC potentials at entrance and exit lenses, allows for efficient ion extraction and scanning by controlling the frequency and magnitude of the oscillating potential, enabling high extraction efficiencies and rapid scan rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional radial and axial ejection mechanisms are used, then ions can be extracted from the trap, but extraction efficiency and scanning speed are limited
Solution Approach 1:
The patent applies dynamic voltage control to the end caps, switching between DC and oscillating potentials in real-time. During ion accumulation, a DC potential maintains stable trapping. During extraction, an oscillating potential with non-zero second derivative dynamically modulates the field to efficiently eject ions. This dynamic adaptation resolves the contradiction by optimizing the field configuration for each operational phase, achieving both high extraction efficiency and rapid scanning.
Solution Approach 2:
The invention changes the temporal characteristics of the potential field by applying oscillating voltages with specific frequency and amplitude parameters to the end caps. The oscillating potential parameters are tuned to match ion motion frequencies, enabling resonant excitation and efficient ejection. This parameter modulation allows rapid ion scanning while maintaining high extraction efficiency, overcoming the limitations of conventional static or simple pulsed fields.
2Speed
If oscillating potential with non-zero second derivative is applied, then ion scanning speed increases, but system complexity increases
Solution Approach 1:
The patent employs periodic oscillating potentials applied to the end caps with frequencies matched to ion secular frequencies. This periodic action creates resonant conditions that efficiently transfer energy to ions, enabling rapid scanning. The periodic nature simplifies the control system compared to arbitrary waveforms, as only frequency and amplitude parameters need adjustment. This resolves the contradiction by achieving high scanning speed through a relatively simple periodic drive mechanism.
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 enhances ion extraction efficiency and scanning speed, producing high-quality mass spectra while accommodating a wide range of ion masses, and allows for ion fragmentation to aid in identification.
Implementation Method 1
An oscillating on-axis potential is applied to the linear ion trap. The oscillating on-axis potential has a non-zero 2nd derivative with time. Ions display frequencies of motion that are mass dependent along the longitudinal axis.
Implementation Method 2
DC potentials are applied to the entrance and exit lenses to provide fringing fields at the ends of the trap
Implementation Method 3
An RF potential is applied to the X and Y poles. Some ions, depending on the characteristics of the radial trapping potential, are trapped within the rod set
Implementation Method 4
Application of an excitation signal, such as dipolar excitation, to the exit lens provides for a means of scanning the ions longitudinally out of the trap
Data Source
AI summary
The invention provides a multipole ion trap. The trap has a longitudinal axis. An oscillating on-axis potential is set up along the longitudinal axis, providing a potential well in which ions are trapped. In some embodiments, rods forming the poles are symmetrically and equidistantly positioned about the longitudinal axis and RF signal with different magnitudes are applied to the poles. In other embodiments, the rods are not positioned symmetrically about the longitudinal axis and the RF signals applied to the poles may have the same or different magnitudes. Poles used in the invention may include two or more rods. An ion trap according to the invention may include more than two poles, and in some embodiments, a third or additional pole may be added to provide the oscillating on-axis potential. The ion trap may be used mass selectively scan ions, fragment ions and to trap and separate differently charged ions, among other uses.