Orthogonal Accelerator Ion Guide for MR-TOF Mass Spectrometer Duty Cycle
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Solution Overview
Problem
Multi-reflecting time-of-flight mass spectrometers (MR-TOF MS) face limitations in duty cycle due to ion scattering, space charge effects, and low repetition rates, which restrict the conversion of continuous ion beams into ion pulses, affecting resolution and mass accuracy, especially when coupled with ion trap sources.
Innovation Solution
The implementation of a multi-reflecting time-of-flight mass spectrometer with an orthogonal accelerator and a radio frequency gas-filled ion guide for periodic modulation of axial ion velocity, along with an electrostatic trap, to enhance the duty cycle by orienting the ion beam across the trajectory plane and synchronizing ion delivery with orthogonal acceleration pulses, allowing multiple reflections and extended ion packets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ion trap sources are used to accumulate ions, then ion current can be increased, but ion scattering on gas and space charge effects worsen, limiting the ion current that can be converted into ion pulses
Solution Approach 1:
A linear ion trap is introduced as an intermediary device between the ion source and the orthogonal accelerator. This linear trap structure reduces space charge effects compared to three-dimensional traps while allowing accumulation of higher ion currents. The trap periodically ejects ion bunches to the orthogonal accelerator, mediating between continuous ion production and pulsed injection requirements.
Solution Approach 2:
The ion beam is segmented into discrete ion bunches by the linear ion trap operating in a pulsed ejection mode. Instead of continuous ion flow, ions are accumulated and then released in controlled bunches, which reduces space charge effects during transport and allows better control of ion current intensity delivered to the analyzer.
2Manufacturing precision
If orthogonal acceleration is used to convert continuous ion beam into ion pulses, then time spread can be reduced to 1 ns, but duty cycle drops below 1 percent due to longer flight times and lower repetition rates in MR-TOF
Solution Approach 1:
Ions are pre-bunched in the linear ion trap before being injected into the orthogonal accelerator. This preliminary bunching action creates compact ion packets with reduced time spread before they enter the flight path, maximizing the efficiency of the orthogonal acceleration process and improving duty cycle by ensuring that ions are ready for immediate pulsed extraction.
Solution Approach 2:
The linear ion trap operates continuously to accumulate ions from the ion source, maintaining a steady supply of ions ready for ejection. This continuous accumulation process ensures that the orthogonal accelerator receives a continuous stream of ion bunches, maximizing the duty cycle by keeping the ion production and injection process ongoing without interruption.
3Productivity
If ion packets are extended in the drift direction to increase duty cycle, then more ions can be injected, but the acceptance of the analyzer to ion packet width is limited by the aperture of periodic focusing lenses
Solution Approach 1:
The linear ion trap provides dynamic control over ion bunch length and timing. By adjusting the ejection pulse parameters, the system can optimize ion packet dimensions to match the analyzer's acceptance aperture while maintaining high duty cycle. The dynamic ejection mechanism allows adaptation of ion packet characteristics to the specific geometric constraints of the periodic focusing lenses.
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 improves the duty cycle of the MR-TOF MS, enabling efficient conversion of ion flux into ion pulses with reduced time distortions and increased mass range, thereby enhancing resolution and mass accuracy while maintaining full mass range analysis.
Implementation Method 1
an orthogonal accelerator to convert the ion beam into ion packets
Implementation Method 2
a radio frequency gas-filled ion guide for periodic modulation of axial ion velocity
Implementation Method 3
along with an electrostatic trap, to enhance the duty cycle
Implementation Method 4
a planar multi-reflecting analyzer providing multiple reflections of the ion packets within a jig-saw trajectory plane
Data Source
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AI summary
The disclosed apparatus includes a multi-reflecting time-of-flight mass spectrometer (MR-TOF MS) (11) comprising a pair of grid- free ion mirrors (12), a drift space (13), an orthogonal ion accelerator (14), an optional deflector (15), an ion detector (16), a set of periodic lenses (17), and an edge deflector (18). To improve the duty cycle of the ion injection at a low repetition rate dictated by a long flight in the MR-TOF MS, multiple measures may be taken. The incoming ion beam and the accelerator may be oriented substantially transverse to the ion path in the MR-TOF, while the initial velocity of the ion beam is compensated by tilting the accelerator and steering the beam for the same angle. To further improve the duty cycle of any multi-reflecting or multi-turn mass spectrometer, the beam may be time-compressed by modulating the axial ion velocity with an ion guide. The residence time of the ions in the accelerator may be improved by trapping the beam within an electrostatic trap. Apparatuses with a prolonged residence time in the accelerator provide improvements in both sensitivity and resolution.