Curved Ion Guide with DC Confinement for Mass-Independent Ion Transport
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Solution Overview
Problem
Conventional RF ion guides face challenges in confining ions of varying mass-to-charge ratios, leading to losses due to insufficient pseudo-potential force, especially at the entrance of curved gas cells, where ions have high kinetic energy and the confining force is inversely dependent on mass-to-charge ratio.
Innovation Solution
A non-linear ion guide is introduced, featuring a combination of DC and RF voltage applications to create orthogonal potential wells, with DC voltage confining ions in the direction of curvature and RF voltage confining them orthogonally, allowing for mass-independent confinement and minimizing losses by varying voltage amplitudes and frequencies along the guide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RF voltage amplitude is increased to confine higher mass-to-charge ratio ions, then confinement of high mass-to-charge ratio ions is improved, but low mass-to-charge ratio product ions are lost due to mass instability
Solution Approach 1:
The ion guide is divided into multiple zones along the ion trajectory, with each zone having independently controllable DC and RF voltages. This segmentation allows different voltage amplitudes to be applied in different spatial regions, enabling confinement of high mass-to-charge ratio ions in zones where they are injected while maintaining stability for low mass-to-charge ratio product ions in other zones.
Solution Approach 2:
Different regions of the ion guide are assigned different electrical characteristics. The DC voltage amplitude varies along the ion path to provide position-dependent confinement forces. This local differentiation allows the system to address the specific needs of ions at different locations, particularly providing stronger confinement where high mass-to-charge ratio ions are present without globally increasing RF amplitude that would destabilize low mass-to-charge ratio ions.
2Ease of operation
If conventional RF ion guide is used, then ion confinement is achieved through pseudo-potential, but ions of varying mass-to-charge ratios experience insufficient confining force leading to radial losses
Solution Approach 1:
The patent combines DC and RF voltage applications in the ion guide electrodes. The DC voltage component provides a mass-independent confining force that supplements the mass-dependent RF pseudo-potential. This merging of two different voltage types creates a hybrid confinement mechanism that is effective for ions across a wide range of mass-to-charge ratios, addressing the insufficiency of RF-only confinement.
Solution Approach 2:
The system dynamically adjusts voltage parameters (amplitude and frequency) of both DC and RF components along the ion guide. By varying these parameters in different zones, the confinement force can be optimized for different ion types and positions, ensuring reliable confinement throughout the device despite variations in ion mass-to-charge ratio.
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 configuration effectively confines ions of all mass-to-charge ratios during collisional cooling, preventing radial losses and enhancing the stability of ion trajectories within the ion guide, thereby improving the efficiency of mass spectrometry processes.
Implementation Method 1
a first device arranged and adapted to apply a DC voltage to at least some of the electrodes in order to form, in use, a DC potential well which acts to confine ions within the ion guiding region in the first (x) direction
Implementation Method 2
a second device arranged and adapted to apply an AC or RF voltage to at least some of the electrodes in order to form, in use, a pseudo-potential well which acts to confine ions within the ion guiding region in a second (y) direction
Implementation Method 3
The ions may be arranged to have a kinetic energy of between 10 and 100 eV. Ions entering the gas cell lose kinetic energy as they collide with the target gas and eventually reach thermal energy. This process is called collisional cooling.
Data Source
AI summary
A non-linear ion guide is disclosed comprising a plurality of electrodes. An ion guiding region is arranged between the electrodes, and the ion guiding region curves at least in a first direction. A DC voltage is applied to at least some of the electrodes in order to form a DC potential well which acts to confine ions within the ion guiding region in the first direction.