Ion Trap Space Charge Saturation Avoidance

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Solution Overview

Problem

Conventional ion traps suffer from limited dynamic range due to space charge saturation effects at high ion population densities, leading to compromised analytical performance in mass spectrometry, with existing methods reducing duty cycle and sensitivity by requiring pre-scans to estimate and limit ion trap filling times.

Innovation Solution

A mass spectrometer design featuring a first ion trap with a controlled charge capacity, where excess ions are deflected and detected, and subsequently transferred to a second ion trap, allowing for dynamic adjustment of ion accumulation and scanning to maintain analytical performance without exceeding the charge capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional ion traps are used to increase ion population density for improved sensitivity, then the dynamic range and analytical performance are compromised due to space charge saturation effects

Engineering Contradiction:

Improveion population densityVSAvoidanalytical performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The ion trap system is divided into two separate ion traps: a first ion trap for accumulating high ion populations and a second ion trap for analytical measurements. This segmentation allows each trap to operate within its optimal charge capacity range, preventing space charge saturation in the analytical trap while maintaining high sensitivity through accumulation in the first trap.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first ion trap acts as an intermediary device between the ion source and the second analytical ion trap. It temporarily stores and regulates the ion population, controlling the transfer of ions to the second trap to maintain optimal charge capacity and avoid space charge effects during analysis.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If pre-scan methods are used to estimate and limit ion trap filling time to avoid space charge saturation, then the duty cycle and overall sensitivity are reduced

Engineering Contradiction:

Improvespace charge controlVSAvoidduty cycle

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

Ion accumulation in the first ion trap is performed in advance before the analytical measurement in the second trap. This preliminary action allows the system to prepare the optimal ion population ahead of time, eliminating the need for pre-scans and enabling continuous analytical measurements without interruption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system enables continuous analytical measurements in the second ion trap while ions are continuously accumulated in the first trap. The decoupled operation allows both accumulation and analysis to proceed simultaneously without interruption, maximizing the duty cycle and overall productivity.

Inventive Principle:

Principle #20Continuity of useful action

3Quantity of substance

If the charge capacity of the ion trap is increased to accommodate more ions, then space charge saturation effects worsen and mass resolution and measurement precision are compromised

Engineering Contradiction:

Improvetotal charge capacityVSAvoidmass resolution

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The total charge capacity is segmented between two ion traps: the first trap has a higher charge capacity optimized for accumulation, while the second trap has a lower charge capacity optimized for analytical measurements with high mass resolution. This segmentation allows the system to handle large total ion populations while maintaining high resolution during analysis.

Inventive Principle:

Principle #1Segmentation

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 enhances the dynamic range and sensitivity of mass spectrometry by preventing space charge saturation, allowing for continuous ion accumulation and scanning while maintaining analytical performance, thereby improving the overall efficiency of ion trapping and analysis.

Implementation Method 1

Ions are trapped with these devices by inhomogeneous fields modulated at radio frequencies (RF confinement). DC trapping potentials may also be used.

Methodology Applied

Scientific EffectElectrostatic confinement: Electrostatics

Implementation Method 2

conventional commercial Ion traps suffer from limited dynamic range due to the onset of space charge saturation effects at high ion population density

Methodology Applied

Scientific EffectSpace charge effect: Ion Repulsion/Attraction

Implementation Method 3

Ions are trapped with these devices by inhomogeneous fields modulated at radio frequencies (RF confinement)

Methodology Applied

Scientific EffectRF confinement: Electromagnetic Induction

Implementation Method 4

The amount of signal recorded in the pre-scan is then used to estimate the time for which the incoming ion beam should be allowed to fill the analytical ion trap

Methodology Applied

Scientific EffectCharge detection:

Data Source

PatentEP2286439B1Method of avoiding space charge saturation effects in an ion trap

Publication Date: 2015.11.11 MICROMASS UK LTD

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AI summary

A mass spectrometer is provided comprising a first ion trap (2) arranged upstream of an analytical second ion trap (5). The charge capacity of the first ion trap (2) is set at a value such that if all the ions stored within the first ion trap (2) up to the charge capacity limit of the first ion trap (2) are then transferred to the second ion trap (5), then the analytical performance of the second ion trap (5) is not substantially degraded due to space charge effects.