Dual-frequency radiofrequency device for confinement of ions

Abstract

A radio-frequency device for transversely confining ions in an ion region, comprising: a first set of electrodes arranged parallel to one another along a direction of ion movement to define a first transverse boundary of the ion region, and supplied with a first radio-frequency voltage such that opposite phases of the first radio-frequency voltage are applied to adjacent electrodes of the first set; and a second set of electrodes arranged parallel to one another along the direction of ion movement to define a second transverse boundary of the ion region, and supplied with a second radio-frequency voltage such that opposite phases of the second radio-frequency voltage are applied to adjacent electrodes of the second set.wherein the first and second transverse boundaries oppose each other in a transverse direction of the ion region, and the first radio-frequency voltage and the second radio-frequency voltage have different frequencies, wherein the electrodes of the first and second sets do not completely enclose the cross-sectional profile of the ion region, wherein additional electrodes or electrode segments are supplied with repulsive DC potentials to transversely confine the ions in subregions of the ion region that are not adjacent to the electrodes of the first or second set, and wherein DC potentials are applied to electrodes of the first or second set, wherein the repulsive DC potentials applied to the additional electrodes or electrode segments have a DC offset relative to the DC potentials applied to adjacent electrodes of the first and second sets.

Claims

[1] A radio frequency device for transverse confinement of ions in an ion region, comprising: a first set of electrodes arranged parallel to one another along a direction of ion movement to define a first transverse boundary of the ion region, and supplied with a first radio-frequency voltage such that opposite phases of the first radio-frequency voltage are applied to adjacent electrodes of the first set; and a second set of electrodes arranged parallel to each other along the direction of ion movement to define a second transverse boundary of the ion region, and supplied with a second radio-frequency voltage such that opposite phases of the second radio-frequency voltage are applied to adjacent electrodes of the second set, wherein the first and second transverse boundaries are opposite each other in a transverse direction of the ion region and the first radio-frequency voltage and the second radio-frequency voltage have different frequencies, wherein the electrodes of the first and second sets do not completely enclose the cross-sectional profile of the ion region, wherein additional electrodes or electrode segments are supplied with repulsive DC potentials in order to transversely confine the ions in partial regions of the ion region that are not adjacent to the electrodes of the first or second set, and wherein DC potentials are applied to electrodes of the first or second set, wherein the repulsive DC potentials applied to the additional electrodes or electrode segments have a DC offset relative to the DC potentials applied to adjacent electrodes of the first and second sets. [2] The high frequency device according to claim 1, characterized by that the first and second high-frequency voltages differ by more than 10%. [3] The high-frequency device according to one of claims 1 or 2, characterized bythat the electrodes of the respective first and second sets have a relative distance S along the direction of ion movement and the first and second transverse boundaries have a relative distance D from each other in the transverse direction, wherein the ratio D:S in at least one section of the radio frequency device along the direction of ion movement is less than 10. [4] The high-frequency device according to any one of claims 1 to 3, characterized by that the electrodes of the first set have a relative spacing equal to a relative spacing of the electrodes of the second set, wherein the arrangement of the electrodes of the second set is offset relative to the electrodes of the first set along the direction of ion movement by a predetermined amount. [5] The high-frequency device according to any one of claims 1 to 4, characterized bythat a plurality of electrodes of the first and / or second set have a rod-shaped section with a round cross-section. [6] The high frequency device according to claim 5, characterized by that a ratio of a diameter of the round cross-section to a distance between the adjacent rod-shaped sections is approximately two to three (2:3). [7] The high-frequency device according to any one of claims 1 to 4, characterized by that a cross-sectional profile of the ion region is convex. [8] The high-frequency device according to any one of claims 1 to 4, characterized by that a cross-sectional profile of the ion region is non-convex. [9] The high-frequency device according to any one of claims 1 to 8, characterized by that the ion region has an elongated cross-sectional profile perpendicular to the direction of ion motion with a long dimension and a short dimension. [10] The high-frequency device according to any one of claims 1 to 9, characterized by that a cross-sectional profile of the ion region varies along the direction of ion motion. [11] The high frequency device according to claim 10, characterized by that the cross-sectional profile at the input of the high-frequency device is larger than at its output. [12] The high-frequency device according to any one of claims 1 to 11, further comprising a DC voltage generator configured to apply repulsive DC potentials to electrodes of the first and / or second set near an entrance and an exit of the ion region such that ions are temporarily stored in the ion region along the direction of ion movement. [13] The radio frequency device according to any one of claims 1 to 11, further comprising a DC voltage generator configured to apply DC potentials to the electrodes of the first and / or second set in the direction of ion movement so that ions are driven through the ion region, accelerated within or into the ion region, or released from the ion region. [14] A mass spectrometric system comprising: an ion source; a mass analyzer; and a radio frequency device for transverse confinement of ions in an ion region, comprising: a first set of electrodes arranged parallel to one another along a direction of ion movement to define a first boundary of the ion region, and supplied with a first radio-frequency voltage such that opposite phases of the first radio-frequency voltage are applied to adjacent electrodes of the first set; and a second set of electrodes arranged parallel to one another along said direction of ion movement to define a second boundary of the ion region, and supplied with a second radio-frequency voltage such that opposite phases of the second radio-frequency voltage are applied to adjacent electrodes of the second set, wherein the first and second transverse boundaries are opposite each other in a transverse direction, the first high-frequency voltage and the second high-frequency voltage have different frequencies, wherein the electrodes of the first and second sets do not completely enclose the cross-sectional profile of the ion region, wherein additional electrodes or electrode segments are supplied with repulsive DC potentials in order to transversely confine the ions in partial regions of the ion region that are not adjacent to the electrodes of the first or second set, and wherein DC potentials are applied to electrodes of the first or second set, wherein the repulsive DC potentials applied to the additional electrodes or electrode segments have a DC offset relative to the DC potentials applied to adjacent electrodes of the first and second sets. [15] The mass spectrometric system according to claim 14, characterized bythat the electrodes of the respective first and second sets have a relative distance S along the direction of ion movement and the first and second boundaries have a relative distance D from each other in the transverse direction, wherein the ratio D:S in at least a portion of the radio frequency device along the direction of ion movement is less than 10. [16] The mass spectrometric system according to any one of claims 14 or 15, characterized by that the electrodes of the first set have a relative spacing equal to a relative spacing of the electrodes of the second set, wherein the arrangement of the electrodes of the second set is offset relative to the electrodes of the first set along the direction of ion movement by a predetermined amount. [17] The mass spectrometric system of any one of claims 14 to 16, further comprising an ion mobility separator between the ion source and the mass analyzer, said ion mobility separator comprising the radio frequency device. [18] The mass spectrometric system according to claim 17, characterized by that the ion mobility separator further comprises a gas flow along the direction of ion movement and a DC voltage generator, wherein the DC voltage generator is configured to supply DC potentials to the electrodes of the first and second sets to generate a DC electric field gradient along the direction of ion movement that counteracts a force of the gas flow so that ions are stored during an accumulation phase and separated according to ion mobility, and wherein the DC voltage generator is configured to vary the DC potentials applied to the electrodes of the first and second sets such that ions are released from the ion mobility separator during an elution phase separately in time according to the ion mobility. [19] The mass spectrometric system according to claim 18, characterized by that the ion region has an elongated cross-sectional profile perpendicular to the direction of ion motion with a long dimension and a short dimension. [20] The mass spectrometric system of any one of claims 14 to 19, further comprising a fragmentation cell between the ion source and the mass analyzer, said fragmentation cell comprising the radio frequency device. [21] The mass spectrometric system according to claim 20, characterized byin that the fragmentation cell is filled with a collision gas and further comprises a DC voltage generator configured to apply DC potentials to the electrodes of the first and / or second set so that ions are accelerated into a collision gas and the fragment ions resulting from collision-induced dissociation are driven through the ion region. [22] The mass spectrometric system according to any one of claims 14 to 21, characterized by that the mass analyzer is a time-of-flight mass analyzer and comprises the radio-frequency device which is part of at least one orthogonal ion injection accelerator, a field-free flight path or a reflector.

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