Ion Beam Attenuator for Mass Spectrometer Space Charge Control
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Solution Overview
Problem
Conventional ion trap mass analyzers face challenges with space charge effects, leading to variable cycle times and uncertainties in ion measurement due to fluctuating ion currents, which result in reduced sensitivity and mass-to-charge ratio discrimination.
Innovation Solution
A method involving an ion beam attenuation device that switches between low and high transmission modes to maintain a constant ion trap fill time, independent of the ion current, using an electrostatic lens or electrodes to control the ion beam and accumulate ions for a fixed period, thereby averaging out fluctuations and minimizing space charge issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the ion trap fill time is adjusted based on ion current to avoid space charge effects, then space charge degradation is reduced, but cycle time becomes variable and measurement precision deteriorates
Solution Approach 1:
The patent implements feedback control by measuring the ion current and using this information to adjust the ion trap fill time dynamically. The system continuously monitors ion current levels and adjusts the accumulation time accordingly, creating a closed-loop control system that optimizes ion population while maintaining consistent cycle times for quantitative accuracy.
Solution Approach 2:
The patent applies preliminary action by measuring the ion current before the ion trap filling process and using this pre-measured information to determine the appropriate fill time. This advance measurement and planning ensures that the ion trap is filled to the optimal population level without exceeding space charge limits, while maintaining predictable cycle times.
2Quantity of substance
If the ion trap fill time is extended to accumulate more ions, then sensitivity improves, but space charge effects worsen and mass-to-charge ratio discrimination increases
Solution Approach 1:
The patent applies dynamics by making the ion trap fill time adjustable and adaptive rather than fixed. The system dynamically adjusts the accumulation time based on real-time ion current measurements, allowing the ion population to be optimized for each specific operating condition. This dynamic control enables the system to accumulate sufficient ions for high sensitivity while preventing excessive accumulation that would cause space charge effects.
3Productivity
If the ion trap fill time is reduced to decrease cycle time, then productivity improves, but ion population decreases and sensitivity worsens
Solution Approach 1:
The patent applies parameter changes by adjusting the ion trap fill time based on measured ion current levels. When ion current is high, the fill time is reduced to maintain consistent cycle times and improve productivity. When ion current is low, the fill time is extended to ensure sufficient ion population for maintaining sensitivity. This adaptive parameter adjustment resolves the contradiction between productivity and sensitivity.
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 ensures a consistent cycle time, reduces sensitivity variations, and minimizes mass-to-charge ratio discrimination, allowing for more reliable and efficient ion accumulation and analysis.
Implementation Method 1
using an electrostatic lens or electrodes to control the ion beam
Implementation Method 2
A method involving an ion beam attenuation device that switches between low and high transmission modes to maintain a constant ion trap fill time
Implementation Method 3
A method involving an ion beam attenuation device that switches between low and high transmission modes to maintain a constant ion trap fill time
Implementation Method 4
accumulate ions for a fixed period, thereby averaging out fluctuations and minimizing space charge issues
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
A mass spectrometer is disclosed wherein an ion beam attenuator (23) is arranged upstream of an ion trap mass analyser (20). An ion tunnel ion trap comprising an upstream ion accumulation section (21) and a downstream ion accumulation section (22) is arranged upstream of the ion beam attenuator (23). Ions are released from the ion tunnel ion trap and the intensity of the ion beam which is transmitted to the ion trap mass analyser (20) is controlled by the ion beam attenuator (23). The fill time during which ions are admitted into the ion trap mass analyser (20) remains substantially constant and is substantially independent of the intensity of the ion beam.