Oblique Parallel Electrodes for TOF Mass Spectrometer Ion Acceleration
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Solution Overview
Problem
Time-of-Flight (TOF) mass spectrometers face limitations in sample throughput due to high turn around time aberration and low duty cycle, which restricts their sensitivity and resolution, especially in orthogonal acceleration instruments, leading to inefficient use of solvents and increased environmental impact.
Innovation Solution
The use of parallel electrodes inclined at an oblique angle to the incoming ion beam allows for full-width sampling and reduced turn around time, combined with oversampling techniques and ion beam conditioning to enhance duty cycle and sensitivity/resolution characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orthogonal acceleration is used to accelerate ions into the TOF mass analyser, then the ion beam can be accelerated efficiently, but the turn around time aberration increases and duty cycle remains low (30%)
Solution Approach 1:
The patent applies asymmetry by using parallel electrodes inclined at an oblique angle (not perpendicular) to the incoming ion beam. This asymmetric configuration allows the ion beam to enter the acceleration region at an angle, enabling full-width sampling of the expanded beam while reducing the turn around time aberration that plagues conventional orthogonal acceleration systems.
Solution Approach 2:
The invention introduces a dimensional change by transitioning from orthogonal (90-degree) acceleration to oblique angle acceleration. This angular dimensionality change allows ions to be sampled across the full width of the expanded beam while maintaining reduced turn around time, effectively adding a geometric dimension to the acceleration process that resolves the throughput-time contradiction.
2Loss of time
If the extraction field is increased to minimize turn around time, then the turn around time aberration is reduced, but the energy spread imparted to the beam increases
Solution Approach 1:
The patent changes the geometric parameter of the acceleration field orientation from orthogonal to oblique angle. This parameter change allows the system to achieve low turn around time with reduced energy spread simultaneously, as the oblique configuration optimizes the relationship between extraction field strength and energy impartation to the ion beam.
3Productivity
If conventional sampling mode is used, then the instrument operation is simple, but the duty cycle is limited to 30%
Solution Approach 1:
The invention enables continuous useful action by allowing the ion accelerator to operate at higher repetition rates through oblique angle acceleration. The full-width sampling capability means ions are continuously available for acceleration without the need to wait for maximum mass ions to reach the detector, maintaining high duty cycle operation while keeping the system relatively simple.
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 increases the sample throughput by an order of magnitude, improving the sensitivity and resolution of TOF instruments, reducing solvent usage, and making them more cost-effective and environmentally friendly.
Implementation Method 1
a pulsed acceleration stage orientated parallel to the incoming ion beam
Implementation Method 2
The parallel electrodes are preferably inclined to the incoming ion beam at an angle θ=tan−1(δvx/δvz), where δvz and δvx are the axial and transverse velocity spreads of said incoming ion beam. Voltages are then reduced and the fill up part of the cycle begins again.
Implementation Method 3
Resolution of these instruments can be increased by use of an ion mirror called a Reflectron. The Reflectron compensates for the energy spread imparted to the ion beam during the acceleration process.
Implementation Method 4
Ions typically emanate from upstream RF cooling devices and beam conditioning is employed to control the ratio of the transverse to axial energy spreads in the beam.
Implementation Method 5
Transverse expansion of the ion beam by a certain factor leads to a consequential reduction in velocity spread by the same factor in said transverse direction, this is a due to conservation of phase space known as Liouville's theorem.
Data Source
AI summary
A pulsed accelerator for a Time of Flight mass spectrometers comprising a set of parallel electrodes. The accelerator is inclined at an oblique angle to the incoming ion beam defined by the ratio of the incoming ion beam velocity spreads axial and transverse to the beam. Additionally a deflection electrode is included to deflect unwanted ions away from the detector during the fill cycle of the accelerator.