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DE-102023205701-B4 - GAS RETAINING ION GUIDE DEVICE WITH AXIAL ACCELERATION

DE102023205701B4DE 102023205701 B4DE102023205701 B4DE 102023205701B4DE-102023205701-B4

Abstract

A gas-retaining ion guide device, comprising: a. a plurality of RF electrodes (12, 12a - 12d) extending from an input to an output of the ion guidance device and distributed around an ion region of the ion guidance device in different respective angular positions relative to a central axis, such that when different phases of a predetermined RF voltage are applied to adjacent RF electrodes (12, 12a - 12d), an RF electric field is generated which provides for confinement of ions in the ion region; and b. a plurality of DC electrodes (14, 14a - 14d) extending from the inlet to the outlet of the ion guidance device and distributed around the ion region in angular positions relative to the central axis, which lie between the angular positions of the RF electrodes (12, 12a - 12d), wherein each DC electrode (14, 14a - 14d) has a conductive surface (24) and provides a gas seal between two adjacent RF electrodes (12, 12a - 12d) which inhibits a gas flow from the ion region in a radial direction, wherein at least some of the conductive surfaces (24) of the DC electrodes (14, 14a - 14d) have a radial distance from the central axis which changes between the inlet and the outlet of the ion guidance device.

Inventors

  • Urs Steiner
  • Felician Muntean

Assignees

  • BRUKER SWITZERLAND AG

Dates

Publication Date
20260513
Application Date
20230619
Priority Date
20220630

Claims (20)

  1. A gas-retaining ion guidance device comprising: a. a plurality of RF electrodes (12, 12a - 12d) extending from an input to an output of the ion guidance device and surrounding an ion area of the ion guidance device in various respective angular positions relative to are distributed along a central axis such that when different phases of a predetermined RF voltage are applied to adjacent RF electrodes (12, 12a - 12d), an electric RF field is generated which provides confinement of ions in the ion region; and b. a plurality of DC electrodes (14, 14a - 14d) extending from the inlet to the outlet of the ion guidance device and distributed around the ion region in angular positions relative to the central axis, which lie between the angular positions of the RF electrodes (12, 12a - 12d), wherein each DC electrode (14, 14a - 14d) has a conductive surface (24) and provides a gas seal between two adjacent RF electrodes (12, 12a - 12d) which inhibits a gas flow from the ion region in a radial direction, wherein at least some of the conductive surfaces (24) of the DC electrodes (14, 14a - 14d) have a radial distance from the central axis which changes between the inlet and the outlet of the ion guidance device.
  2. Gas-retaining ion guide device according to Claim 1 , wherein a common DC voltage is applied to each of the conductive surfaces (24) of the DC electrodes (14, 14a - 14d).
  3. Gas-retaining ion guide device according to Claim 1 or Claim 2 , in which two of the DC electrodes (14, 14a - 14d) have conductive surfaces (24) on opposite sides of the central axis with a radial distance (X i , X 0 ) from the central axis, which increases or decreases from the input to the output of the ion guidance device.
  4. Gas-retaining ion guide device according to Claim 3 , wherein a direct current voltage applied to the conductive surfaces (24) of the direct current electrodes (14, 14a - 14d) has a polarity that repels or attracts the ions in the ion guidance device.
  5. Gas-retaining ion guide device according to one of the Claims 1 until 4 , wherein the DC electrodes (14, 14a - 14d) are placed between opposing slots (20) in the conductive material of adjacent RF electrodes (12, 12a - 12d).
  6. Gas-retaining ion guide device according to one of the Claims 1 until 5 , in which the conductive surfaces (24) of the DC electrodes (14, 14a - 14d) are further away from the central axis than the RF field generating surfaces (18, 18a - 18d) of the RF electrodes (12, 12a - 12d) that contribute to the electric RF field in the ionic region.
  7. Gas-retaining ion guide device according to Claim 6 , wherein each of the DC electrodes (14, 14a - 14d) has a substantially elongated cross-sectional profile in a plane perpendicular to the central axis and wherein the conducting surface (24) of each DC electrode (14, 14a - 14d) is perpendicular to a radial direction relative to the central axis.
  8. Gas-retaining ion guide device according to Claim 7 , in which the RF field generating surfaces (18, 18a - 18d) of two adjacent RF electrodes (12, 12a - 12d) are separated by a gap (d e ) that lies between the central axis and the conducting surface (24) of a nearby DC electrode (14, 14a - 14d).
  9. Gas-retaining ion guide device according to Claim 8 , where the size of the predetermined gap (d e ) is constant from the entrance to the exit.
  10. Gas-retaining ion guide device according to Claim 8 , where the size of the conductive surface (24) of the nearest DC electrode (14, 14a - 14d) is such that it is intersected by every straight path from the ion region passing through the gap.
  11. Gas-retaining ion guide device according to one of the Claims 1 until 10 , in which the conductive surfaces (24) of the DC electrodes (14, 14a - 14d) have a minimum distance (d gap ) to each conductive surface of an RF electrode (12, 12a - 12d) sufficient to prevent electric arcs.
  12. Gas-retaining ion guide device according to one of the Claims 1 until 11 , wherein each direct current electrode (14, 14a - 14d) comprises an insulating substrate (23) on which its conductive surface (24) is located.
  13. Gas-retaining ion guide device according to Claim 12 , wherein the conductive surface (24) of each DC electrode (14, 14a - 14d) covers only a part of the substrate (23) and the substrate (23) is in contact with conductive material of adjacent RF electrodes (12, 12a - 12d).
  14. Gas-retaining ion guide device according to one of the Claims 1 until 13 , in which a number of the DC electrodes (14, 14a - 14d) are dimensioned such that a gas seal is provided between each two adjacent RF electrodes (12, 12a - 12d) so that a gas flow from the ion region is inhibited in all radial directions.
  15. Ion collision cell, which includes a gas-retaining ion guidance device according to Claim 14 includes.
  16. Ion collision cell according to Claim 15 , which further comprises a gas inlet located between the inlet and outlet of the gas-retaining ion guide device and through which a collision gas is supplied to the ion area during operation.
  17. A method for accelerating ions in a gas-retaining ion guidance device comprising a plurality of RF electrodes (12, 12a-12d) extending from an inlet to an outlet of the ion guidance device and distributed around an ion region of the ion guidance device at different respective angular positions relative to a central axis, such that when different phases of a predetermined RF voltage are applied to adjacent RF electrodes (12, 12a-12d), an RF electric field is generated which causes confinement of ions in the ion region, the method comprising arranging a plurality of DC electrodes (14, 14a-14d) in the ion guidance device extending from the inlet to the outlet of the ion guidance device and distributed around the ion region at angular positions relative to the central axis between the angular positions of the RF electrodes (12, 12a-12d). 12d), wherein each DC electrode (14, 14a - 14d) has a conductive surface (24) and provides a gas seal between two adjacent RF electrodes (12, 12a - 12d) that inhibits a gas flow from the ion region in a radial direction, wherein at least some of the conductive surfaces (24) of the DC electrodes (14, 14a - 14d) have a radial distance from the central axis that changes between the inlet and outlet of the ion guidance device.
  18. Procedure according to Claim 17 , wherein the arrangement of a plurality of DC electrodes (14, 14a-14d) in the ion guidance device comprises the arrangement of two of the DC electrodes (14, 14a - 14d) on opposite sides of the central axis, the conductive surfaces (24) having a radial distance from the central axis which increases or decreases from the inlet to the outlet of the ion guidance device.
  19. Procedure according to Claim 17 or Claim 18 , wherein the arrangement of a plurality of DC electrodes (14, 14a-14d) in the ion guidance device comprises the placement of the DC electrodes (14, 14a - 14d) between opposing slots (20, 20a - 20d) in the conductive material of adjacent RF electrodes (12, 12a - 12d).
  20. Procedure according to one of the Claims 17 until 19 , wherein each DC electrode (14, 14a - 14d) comprises an insulating substrate (23) on which its conductive surface (24) is located, the insulating substrate (23) being in contact with the conductive material (24) of adjacent RF electrodes (12, 12a - 12d).

Description

BACKGROUND OF THE INVENTION AREA OF INVENTION The present invention relates generally to the field of mass spectrometry and ion mobility spectrometry and in particular to gas-filled ion guidance devices, especially lens-free collision cells for ions. Description of the state of the art In analytical systems using mass spectrometry and/or ion mobility spectrometry, it is necessary to ionize a sample material with an ion source and transport the generated ions to an analytical instrument. Often, it is also desirable to modify the ions generated in the ion source by fragmenting them into smaller molecular ions. This can be achieved by introducing the sample ions into a collision cell, where they collide with neutral gas molecules. Typically, a specially selected gas, such as argon, nitrogen, or helium, is introduced into a higher-pressure area within the collision cell, causing the ions to collide with molecules of the introduced gas. The resulting fragment or product daughter ions then exit the collision cell and are directed to an ion analyzer. In such a collision cell, the number of collisions depends on the gas pressure and the reaction time, which is related to the length of the cell's collision path and the ion velocity. The relatively high pressure inside the collision cell must therefore be precisely controlled, while other components of an ion analysis system are often kept in a vacuum. This is especially true for a "lens-free" collision cell, which eliminates the need for narrow apertures and ion-focusing lenses at the cell's inlet and outlet. Such a lens-free collision cell is described in US Patent No. US 8,481,929 B2 shown, whose basic configuration in the 1 and 2 is shown. 1 Figure 1 is a schematic top view of the collision cell 260 mentioned above, which is arranged to receive the ions emitted by a mass analyzer 225. After passing through the collision cell 260, the ions are directed to a second mass analyzer 227. As shown, the ions are deflected by 180° in the collision cell 260, which keeps the overall system compact. The collision cell 260 consists of four semicircular conductive elements that generate the field required for ion transport. The four elements are made of conductive material and are attached to a common insulating plate so that their orientation is referenced to a single plane. This ensures precise alignment of the poles during manufacturing and at various operating temperatures. As in the cross-section of 2 along line AA in 1 As shown, each of the electrodes 361-364 of the quadruple collision cell consists of a conductive semicircular element, and all four electrodes 361-364 are attached along their length to the insulating plate 365. This provides a common reference plane for the electrode surfaces and ensures correct alignment during assembly. Also in 2 Four elongated seals 366, 368 are visible, each positioned between two adjacent electrodes. Seals 366, 368 are thin insulating strips that follow the shape of the collision cell and form a tunnel around an ion transport pathway, helping to retain the injected gas. DE 10 2012 211 593 A1 Disclosing a lens-free collision cell of a mass spectrometer with four semicircular RF electrodes on a common reference plate, forming an ion transport channel. The elongated sealing surfaces are designed as thin strips arranged laterally around the entire channel length behind the electrode interspaces (g). A similar collision cell is shown in the US 2013/0015349 A1 became known. US 6,111,250 A reveals a quadrupole collision cell of a mass spectrometer with an axial DC field for accelerating the ion beam, generated, for example, by conical rods, obliquely arranged rods, segmented rods, or shells around rods. US 7,675,031 B2 describes auxiliary electrodes as arrays of finger electrodes on thin substrates (e.g. printed circuit board material) that are inserted between the main RF electrodes of a multipole to generate drag fields. US 2020/0194244 A1 This describes a multipole collision cell with electrodes to which an RF potential is applied. In the end regions, a pure RF field is generated (radial focusing), and in a central section, an axial DC field is generated (ion acceleration). SUMMARY OF THE INVENTION According to the present invention, a gas-retaining ion guide device is provided, which is similar to the guide devices described above from the prior art, but additionally provides a means for ion acceleration that is advantageous in numerous applications. In an exemplary embodiment of the invention, the gas-retaining ion guide device has a plurality of RF electrodes extending from an input to an output of the ion guide device. The RF electrodes are distributed around a central axis of an ion guide region of the conductor at different angular positions relative to a central axis, such that when different, usually opposite, phases of a predetermined RF voltage are applied to adjacent electrodes, an RF electric field is generated that ensures