Charge detection for ion accumulation control

Patent metadata

Field	Value
Publication number	US-12300481-B2
Application number	US-202318314506-A
Country	US
Kind code	B2
Filing date	May 9, 2023
Priority date	May 9, 2022
Publication date	May 13, 2025
Grant date	May 13, 2025

Abstract

Provided herein are methods and systems for controlling the number of ions in a batch of ions accumulated in an ion trap. The ion trap comprises one or more detection electrodes configured to detect image current signals from ions accumulated within the ion trap. An ion or group of ions passed to the ion trap is caused to impact upon one or more of the detection electrode(s) of the ion trap so as to provide a detected signal. An ion current or charge of the ion or group of ions is determined from the detected signal, and the determined ion current or charge of the ion or group of ions is used to control the number of ions in a batch of ions subsequently accumulated in the ion trap.

First claim

The invention claimed is:

1. A method of operating an analytical instrument that comprises an ion trap, the ion trap comprising one or more detection electrodes, wherein one or more of the detection electrode(s) are configured to detect image current signals from ions accumulated within the ion trap, the method comprising:
operating the instrument in a first mode of operation in which ions passed to the ion trap are caused to impact upon one or more of the detection electrode(s) of the ion trap, and passing a group of ions to the ion trap such that the group of ions is caused to impact upon one or more of the detection electrode(s) of the ion trap so as to provide a detected signal;
determining an ion current or charge of the group of ions from the detected signal; and
using the determined ion current or charge of the group of ions to control the number of ions in a batch of ions subsequently accumulated in the ion trap;
wherein in the first mode of operation, ions are caused to impact upon one or more of the one or more detection electrode(s) that are configured to detect image current signals from ions accumulated within the ion trap; or
wherein in the first mode of operation, ions are caused to impact upon one or more of the one or more detection electrode(s) that are electrically connected to one or more of the detection electrode(s) that are configured to detect image current signals from ions accumulated within the ion trap.

2. The method of claim 1 , further comprising:
operating the instrument in a second mode of operation in which ions passed to the ion trap are caused to become trapped within the ion trap;
accumulating the batch of ions in the ion trap; and
analysing the batch of ions by using the one or more detection electrodes to detect image current signals from the batch of ions accumulated within the ion trap.

3. The method of claim 2 , wherein:
operating the instrument in the first mode of operation comprises applying a first set of one or more voltages to the ion trap, wherein the first set of one or more voltages is configured to cause ions passed to the ion trap to impact upon one or more of the detection electrode(s) of the ion trap; and
operating the instrument in the second mode of operation comprises applying a second different set of one or more voltages to the ion trap, wherein the second set of one or more voltages is configured to cause ions passed to the ion trap to become trapped within the ion trap.

4. The method of claim 3 , wherein:
the first set of one or more voltages includes one or more constant voltages; and
the second set of one or more voltages includes one or more dynamic voltages.

5. The method of claim 2 , wherein the ion trap is an electrostatic ion trap having an inner electrode arranged along an axis and two outer detection electrodes spaced apart along the axis and surrounding the inner electrode;
wherein operating the instrument in the first mode of operation comprises applying a constant voltage to the inner electrode; and
wherein operating the instrument in the second mode of operation comprises varying the voltage applied to the inner electrode.

6. The method of claim 2 , wherein passing the group of ions to the ion trap comprises passing the group of ions to the ion trap via one or more ion optical devices arranged upstream of the ion trap;
wherein operating the instrument in the first mode of operation comprises applying a first set of one or more voltages to the one or more ion optical devices, wherein the first set of one or more voltages is configured to cause ions passed to the ion trap to impact upon one or more of the detection electrode(s) of the ion trap; and
wherein operating the instrument in the second mode of operation comprises applying a second different set of one or more voltages to the one or more ion optical devices, wherein the second set of one or more voltages is configured to cause ions passed to the ion trap to become trapped within the ion trap.

7. The method of claim 6 , wherein:
the first set of one or more voltages includes one or more constant voltages; and
the second set of one or more voltages includes one or more dynamic voltages.

8. The method of claim 2 , wherein the one or more ion optical devices comprise a deflector arranged adjacent to an ion entrance of the ion trap;
wherein operating the instrument in the first mode of operation comprises applying a constant voltage to the deflector; and
wherein operating the instrument in the second mode of operation comprises varying the voltage applied to the deflector.

9. The method of claim 1 , wherein the ion trap is a primary ion trap, and the method comprises:
accumulating the group of ions within a secondary ion trap arranged upstream of the primary ion trap;
wherein the step of passing the group of ions to the ion trap comprises passing the group of ions from the secondary ion trap to the primary ion trap, optionally via the one or more ion optical devices.

10. The method of claim 9 , comprising accumulating the group of ions within the secondary ion trap for a set fill time.

11. The method of claim 9 , comprising accumulating the batch of ions in the ion trap by:
accumulating the batch of ions within the secondary ion trap; and
passing the batch of ions from the secondary ion trap to the primary ion trap, optionally via the one or more ion optical devices, so as to accumulate the batch of ions within the primary ion trap.

12. The method of claim 9 , wherein the secondary ion trap is a linear ion trap such as a curved linear ion trap.

13. The method of claim 1 , wherein the method comprises:
subtracting a background signal from the detected signal, wherein the background signal is a signal measured by operating the ion trap in the first mode of operation without passing ions to the ion trap; and
determining the ion current or charge of the group of ions from the detected signal with the background signal subtracted.

14. The method of claim 9 , wherein the method comprises controlling the number of ions in the batch of ions subsequently accumulated in the ion trap by controlling a fill time of ions into the primary ion trap or by controlling a fill time of ions into the secondary ion trap.

15. The method of claim 2 , wherein the method comprises:
operating the instrument in the second mode of operation and accumulating a batch of ions in the ion trap, using the one or more detection electrodes to detect image current signals from the batch of ions accumulated within the ion trap, determining an ion current or charge of the group of ions from the image current signals, and using the determined ion current or charge of the batch of ions to determine a target fill time for a batch of ions subsequently accumulated in the ion trap;
comparing the determined ion current or charge of the group of ions to the determined ion current or charge of the batch of ions; and
adjusting the target fill time based on the comparison.

16. The method of claim 2 , wherein the ion trap comprises detection circuitry comprising a set of one or more transistors, and wherein the same set of one or more transistors is used for both ion current or charge detection in the first mode of operation and for image current detection in the second mode of operation.

17. A method of operating an analytical instrument that comprises a primary ion trap and a secondary ion trap arranged upstream of the primary ion trap, the method comprising:
accumulating a group of ions within the secondary ion trap;
operating the instrument in a first mode of

Assignees

• Thermo Fisher Scient Bremen Gmbh

Inventors

• Hartmer Ralf Günter
• Grinfeld Dmitry
• Makarov Alexander
• Czemper Frank
• Ostermann Robert

Classifications

• H01J49/4225

  Multipole linear ion traps, e.g. quadrupoles, hexapoles · CPC title

• H01J49/027

  detecting image current induced by the movement of charged particles (H01J49/38 takes precedence) · CPC title

• H01J49/4245

  Electrostatic ion traps (H01J49/422 takes precedence) · CPC title

• H01J49/4265 Primary

  Controlling the number of trapped ions; preventing space charge effects · CPC title

• H01J49/025

  Detectors specially adapted to particle spectrometers (data acquisition H01J49/0036; detectors per se G01T, e.g. G01T1/28, G01T1/29) · CPC title