Unbalanced RF Mode Linear Ion Trap Kinetic Energy Spread
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Solution Overview
Problem
Linear ion traps in mass spectrometry systems face challenges in reducing the kinetic energy spread of ions radially ejected, leading to inefficiencies in ion ejection and analysis.
Innovation Solution
The implementation of an unbalanced RF mode with a main RF potential applied to one pair of trap electrodes and a supplemental auxiliary RF potential applied to the other pair, along with a DC bias voltage, to control the kinetic energy distribution of ions during resonant ejection, ensuring a higher percentage of ions are ejected within a specific kinetic energy window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional RF ejection method is used in linear ion trap, then ions can be ejected from the trap, but the kinetic energy spread of ejected ions is large
Solution Approach 1:
The ejection process is divided into two distinct phases: a first ejection voltage applied to initiate ion ejection, followed by a second ejection voltage applied after a time delay to further eject remaining ions. This segmented approach allows control over the kinetic energy distribution while maintaining high ejection efficiency.
Solution Approach 2:
The first ejection voltage is applied in advance to begin the ion ejection process and establish initial kinetic energy distribution. This preliminary action prepares the ion population for subsequent ejection by the second voltage, enabling better control over the final kinetic energy spread.
2Measurement precision
If single ejection voltage is applied, then the ejection process is simple, but the kinetic energy distribution factor is low
Solution Approach 1:
The ejection voltage is made dynamic by applying two different voltages at different time points during the ejection process. The first voltage initiates ejection, and the second voltage, applied after a predetermined time delay, completes the ejection of remaining ions. This dynamic voltage control significantly improves the kinetic energy distribution factor compared to a single static voltage approach.
Solution Approach 2:
The ejection process uses periodic application of voltages with a predetermined time delay between the first and second ejection voltages. This periodic action pattern allows systematic control over ion ejection kinetics, improving energy distribution while maintaining manageable system complexity through regular timing cycles.
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 significantly reduces the kinetic energy spread of ejected ions, improving the Kinetic Energy Distribution Factor to between 60 and 90%, allowing for more precise analysis and increased throughput in mass spectrometry.
Implementation Method 1
In a linear ion trap, ions can be confined radially by a two-dimensional radio frequency (RF) field, and axially by stopping potentials applied to end electrodes
Implementation Method 2
The voltages applied to the ion trap can be adjusted to
Implementation Method 3
Ions can be ejected from the trap by applying the RF voltage to all sections of the trap and utilizing a supplemental dipolar resonance ejection voltage. These changes can cause the ions to become unstable in the direction of dipolar excitation and leave the trapping field
Implementation Method 4
The implementation of an unbalanced RF mode with a main RF potential applied to one pair of trap electrodes and a supplemental auxiliary RF potential applied to the other pair
Implementation Method 5
along with a DC bias voltage, to control the kinetic energy distribution of ions during resonant ejection
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A system for analyzing a sample includes a linear ion trap, an insert DC electrode, a voltage controller, and an RF control circuitry. The linear ion trap includes a first pair of trap electrodes and a second pair of trap electrodes spaced apart from each other and surrounding a trap interior. An electrode of the second pair of trap electrodes includes a trap exit. The insert DC electrode is positioned adjacent to the trap exit. The voltage controller applies a DC voltage to the insert DC electrode. The RF control circuitry applies a main RF voltage to the first pair of trap electrodes, applies a portion of the main RF to the second pair of trap electrodes, increases the main RF applied to the first pair of trap electrodes, and applies an auxiliary RF voltage to the second pair of trap electrodes.