Rotating excitation field in linear ion processing apparatus
AssigneeVarian, Inc.
InventorGregory J. Wells
Life of this patent
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Abstract
Methods for applying an RF field in a two-dimensional electrode structure include applying RF voltages to main electrodes and to compensation electrodes. The voltages on the compensation electrodes may be adjusted to be proportional to the voltages on the main electrodes. The adjustment(s) may be done to optimize the RF field for different modes of operation such as ion ejection and ion dissociation. For dissociation, a supplemental RF dipole may be applied, or two mutually orthogonal dipoles may be applied in phase quadrature to form a circularly polarized field. Electrode structures may include main trapping electrodes, one or more compensation electrodes, one or more ion exit apertures, and means for applying the various desired voltages.
Claims20
A method for forming a circularly polarized RF field in an electrode structure, the electrode structure including a plurality of main electrodes coaxially disposed about a central axis and extending generally in the direction of the central axis, the main electrodes defining an interior space extending along the central axis, the method comprising:
- applying a first RF voltage to at least two of the main electrodes;
- applying a second RF voltage to a compensation electrode disposed in the interior space proximate to a corresponding main electrode at a radial distance from the central axis less than the radial distance of the corresponding main electrode from the central axis;
- applying a third RF voltage between first and second main electrodes spaced apart along a first axis orthogonal to the central axis;
- and
- applying a fourth RF voltage, in phase quadrature with the third RF voltage, between third and fourth main electrodes spaced apart along a second axis orthogonal to the central axis.
An electrode structure for manipulating ions, comprising:
- a plurality of main electrodes coaxially disposed about a central axis and extending generally in the direction of the central axis, the main electrodes defining an interior space extending along the central axis;
- a compensation electrode disposed in the interior space proximate to a corresponding main electrode at a radial distance from the central axis less than the radial distance of the corresponding main electrode from the central axis;
- means for applying a first RF voltage to at least two of the main electrodes;
- means for applying a second RF voltage to the compensation electrode;
- and
- means for forming a circularly polarized RF field in the interior space.
Dependencies are inferred from the claim text.