Mass Spectrometer Electrode Geometry for Ion Acceleration
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Solution Overview
Problem
Conventional mass spectrometry systems with quadrupole electrode systems experience speed dispersion and reduced resolution due to oscillations in ion speed caused by an inclined RF and DC potential gradient, leading to crosstalk and reduced mass spectrum quality.
Innovation Solution
The use of 2n rod-like electrodes with a control unit applying DC and RF voltages to generate a high-frequency multipole electric field, where the distance between facing electrodes is varied from the entrance to the exit to restrain RF electric fields in the z-direction, maintaining a constant RF potential and setting the RF component's potential on the central axis to zero near the exit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a potential gradient of DC component is generated in the collision chamber to accelerate decelerated ions, then ion acceleration is improved, but ion speed oscillation increases causing speed dispersion and resolution reduction
Solution Approach 1:
The patent applies dynamics by making the electrode system configurable between two operational modes: a parallel electrode configuration for high resolution and a focused electrode configuration for high sensitivity. The electrode positions are dynamically adjustable to change the electric field distribution, allowing the system to adapt between acceleration priority and resolution priority based on analytical needs.
Solution Approach 2:
The patent changes the geometric parameter of the electrode system by varying the distance between facing electrodes. In the parallel configuration, electrodes are equidistant to create uniform fields for resolution. In the focused configuration, electrodes are positioned at different distances to create potential gradients for acceleration and sensitivity enhancement.
2Speed
If four rod-like electrodes with gradually changed diameters are alternately disposed to generate DC potential gradient, then ion acceleration is improved, but device complexity increases
Solution Approach 1:
Instead of using gradually changed electrode diameters to generate potential gradients (conventional approach), the patent inverts the approach by using fixed diameter electrodes positioned at varied distances from the central axis. This creates the same potential gradient effect with simpler, more manufacturable electrodes.
Solution Approach 2:
The patent introduces asymmetry in electrode positioning rather than electrode geometry. The facing electrodes are placed at different radial distances from the central axis, creating asymmetric electric field distribution that generates the required potential gradient without requiring asymmetric electrode shapes.
3Speed
If RF voltage and DC voltage are superimposed on electrodes to generate potential gradient, then ion acceleration is improved, but speed dispersion increases leading to crosstalk
Solution Approach 1:
The patent segments the collision chamber into multiple regions with different electrode configurations. The first region uses parallel electrodes for resolution-critical measurements, while the second region uses focused electrodes for acceleration-critical measurements. This segmentation allows each region to optimize for its specific function without compromising the other.
Solution Approach 2:
Different local electrode configurations are applied to different regions of the collision chamber. The parallel electrode configuration provides uniform fields for resolution in one region, while the focused configuration provides accelerated fields for sensitivity in another region. Each local configuration is optimized for its specific analytical requirement.
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 effectively accelerates ions while reducing speed dispersion, achieving high-sensitivity and high-resolution analysis by minimizing ion oscillations and maintaining a stable potential distribution.
Implementation Method 1
a control unit configured to apply a DC voltage U and a radio frequency voltage VRF cos Ωt to the rod-like electrodes to generate a high-frequency multipole electric field equal to or more than a quadrupole electric field between the rod-like electrodes
Implementation Method 2
The potential of the RF component is changed in accordance with a z coordinate, in other words, an RF electric field is generated also in the z direction
Implementation Method 3
one of the plurality of quadrupole electrode systems is filled with a buffer gas and functions as a collision chamber that dissociates (collision induced dissociation) target ions with collision against the buffer gas
Implementation Method 4
passing speed of ions passing through the quadrupole electrode system in the collision chamber is reduced by collision against the buffer gas
Implementation Method 5
there is employed means for generating a potential gradient of a DC component in a direction of travel of the ions
Implementation Method 6
a potential gradient of a DC component is generated on a central axis of the electrode system... ions passing through the inside are accelerated
Data Source
AI summary
Acceleration of decelerated ions and a reduction in the velocity dispersion width of decelerated ions are both achieved, whereby the sensitivity of detected ion sensitivity is improved and resolution is improved. The distance dx between at least one set of facing rod-shaped electrodes among rod-shaped electrodes (4-2-a) to (4-2-d) differs at the inlet part at which ions enter and the outlet part at which ions exit, and the distance dx between the at least one set of facing rod-shaped electrodes is gradually reduced or increased from the inlet part toward the outlet part.