# US 12,191,130 B2 · Charge detection mass spectrometry > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,191,130 B2 - Document ID: US12191130B2 - Status: Granted - Kind: B2 - Application number: 18/495,237 - Filed: 2023-10-26 - Published: 2024-02-22 - Granted: 2025-01-07 - Earliest claimed: 2018-02-22 - Assignees: Micromass UK Limited - Applicants: Micromass UK Limited - Inventors: Keith Richardson; Jeffery Mark Brown; David J. Langridge - Web page: https://patentgrep.com/patent/US12191130B2 ## CPC - H01J 49/0036: {Step by step routines describing the handling of the data generated during a measurement} - H01J 49/027: {detecting image current induced by the movement of charged particles (H01J49/38 takes precedence)} - H01J 49/067: {Ion lenses, apertures, skimmers} - H01J 49/4265: {Controlling the number of trapped ions; preventing space charge effects} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract Disclosed herein are various methods and apparatus for performing charge detection mass spectrometry (CDMS). In particular, techniques are disclosed for monitoring a detector signal from a CDMS device to determine how many ions are present in the ion trap (10) of the CDMS device. For example, if no ions are present the measurement can then be terminated early. Similarly, if more than one ion is present, the measurement can be terminated early, or ions can be removed from the trap (10) until only a single ion remains. Techniques are also provided for increasing the probability of there being a single ion in the trap (10). A technique for attenuating an ion beam is also provided. ## Claims ### Claim 1 An ion beam attenuating apparatus comprising: a first ion beam attenuator that is operable in either a high ion transmission mode or a low ion transmission mode in order to selectively attenuate an ion beam, wherein the output of the first ion beam attenuator is passed through a first gas-filled region; a second ion beam attenuator that is operable in either a high ion transmission mode or a low ion transmission mode in order to selectively attenuate an ion beam; and control circuitry that is configured to: repeatedly switch the first ion beam attenuator between the high and low ion transmission modes to generate a first non-continuous ion beam at the output of the first ion beam attenuator, wherein the first non-continuous ion beam is passed through the gas-filled region and converted into a substantially continuous ion beam thereby before arriving at the second ion beam attenuator; and repeatedly switch the second ion beam attenuator between the high and low ion transmission modes to generate a second non-continuous ion beam at the output of the second ion beam attenuator. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the output of the second ion beam attenuator is passed through a second gas-filled region to generate a substantially continuous attenuated ion beam. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the apparatus is arranged for the substantially continuous attenuated ion beam to be provided from the second gas-filled region to: an ion trap; or an ion detector; or a reaction cell; or a third ion beam attenuator. ### Claim 4 (depends on 2) The apparatus of claim 2, comprising an ion trap configured for trapping a single ion therein, wherein the apparatus is arranged to provide the substantially continuous attenuated ion beam from the second gas-filled region to the ion trap. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the control circuitry is configured to adjust the relative attenuation provided by the first ion beam attenuator and the second ion beam attenuator to achieve a target overall attenuation. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the control circuitry is configured to control the attenuation provided by the first and/or second ion beam attenuators by controlling the frequency of switching between the high and low ion transmission modes. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the control circuitry is configured to: repeatedly switch the first ion beam attenuator between the high and low ion transmission modes at a first frequency; and repeatedly switch the second ion beam attenuator between the high and low ion transmission modes at a second frequency that is different to the first frequency. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the first and/or second ion beam attenuator comprises one or more electrostatic lenses. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the electrostatic lenses comprise one or more electrodes, and wherein the control circuitry is configured to switch between the high and low ion transmission modes by changing one or more voltages applied to the electrodes. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the first and/or second ion beam attenuator is configured to transmit substantially 100% of ions when in the high ion transmission mode. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the first and/or second ion beam attenuator is configured to transmit substantially 0% of ions when in the low ion transmission mode. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein the first gas-filled region comprises an ion guide or a gas collision cell. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises a differential pumping aperture provided at the entrance and/or exit of the first gas-filled region. ### Claim 14 A method of attenuating an ion beam, comprising: passing the ion beam to a first ion beam attenuator and repeatedly switching the first ion beam attenuator between high and low ion transmission modes to generate a first non-continuous ion beam at the output of the first ion beam attenuator; passing the first non-continuous ion beam through a gas-filled region to convert the first attenuated ion beam into a substantially continuous attenuated ion beam; and passing the substantially continuous ion beam to a second ion beam attenuator and repeatedly switching the second ion beam attenuator between high and low ion transmission modes to generate a second non-continuous ion beam at the output of the second ion beam attenuator. ### Claim 15 (depends on 14) The method of claim 14, further comprising passing the second attenuated ion beam through a second gas-filled region to generate a substantially continuous attenuated ion beam. ### Claim 16 (depends on 15) The method of claim 15, comprising providing the substantially continuous attenuated ion beam from the second gas-filled region to: an ion trap; or an ion detector; or a reaction cell; or a third ion beam attenuator. ### Claim 17 (depends on 14) The method of claim 14, wherein the first and/or second ion beam attenuator comprises one or more electrostatic lenses. ### Claim 18 (depends on 14) The method of claim 14, comprising controlling the attenuation provided by the first and/or second ion beam attenuators by controlling the frequency of switching between the high and low ion transmission modes. ### Claim 19 (depends on 14) The method of claim 14, comprising controlling the gas pressure within the first gas-filled region when converting the first attenuated ion beam into the substantially continuous ion beam. ### Claim 20 (depends on 14) The method of claim 14, comprising: the first and/or second ion beam attenuator transmitting substantially 100% of ions when in the high ion transmission mode; and/or the first and/or second ion beam attenuator transmitting substantially 0% of ions when in the low ion transmission mode.