# US 9,040,907 B2 · Method and apparatus for tuning an electrostatic ion trap

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- Number: US 9,040,907 B2
- Document ID: US9040907B2
- Status: Granted
- Kind: B2
- Application number: 14/354,227
- Filed: 2012-10-30
- Published: 2014-09-18
- Granted: 2015-05-26
- Earliest claimed: 2011-10-31
- Assignees: MKS Instruments, Inc.
- Applicants: MKS Instruments, Inc.
- Inventors: Gerardo A. Brucker; G. Jeffery Rathbone; Brian J. Horvath; Timothy C. Swinney; Stephen C. Blouch; Jeffrey G. McCarthy; Timothy R. Piwonka-Corle
- Web page: https://patentgrep.com/patent/US9040907B2

## CPC

- H01J 49/4245: {Electrostatic ion traps (H01J49/422 takes precedence)}
- H01J 27/205: {with electrons, e.g. electron impact ionisation, electron attachment}
- H01J 49/0009: {Calibration of the apparatus}
- H01J 49/0031: {Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence)}
- H01J 49/147: {with electrons, e.g. electron impact ionisation, electron attachment (H01J49/145 takes precedence)}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

An apparatus includes an electrostatic ion trap and electronics configured to measure parameters of the ion trap and configured to adjust ion trap settings based on the measured parameters. A method of tuning the electrostatic ion trap includes, under automatic electronic control, measuring parameters of the ion trap and adjusting ion trap settings based on the measured parameters.

## Claims

### Claim 1

A method of tuning an electrostatic ion trap, the method comprising, under automatic electronic control:
i) measuring parameters of the ion trap, the trap including an ion source having an electron source;
ii) adjusting ion trap settings based on the measured parameters; and
iii) employing the ion trap settings and producing test spectra from a test gas at a specified pressure.

### Claim 2 (depends on 1)

The method of claim 1, wherein adjusting ion trap settings includes adjusting electron source settings.

### Claim 3 (depends on 1)

The method of claim 1, wherein measuring parameters of the ion trap further includes measuring an amount of ions being formed by collisions between electrons and a specified pressure of a test gas as a function of an electron source repeller bias.

### Claim 4 (depends on 3)

The method of claim 3, wherein adjusting ion trap settings further includes increasing the amount of ions being formed at an electron source filament current.

### Claim 5 (depends on 3)

The method of claim 3, further comprising setting the electron source repeller potential bias to a setting that yields a maximum baseline ion current at an electron source filament current.

### Claim 6 (depends on 3)

The method of claim 3, wherein increasing the amount of ions being formed includes increasing the amount of ions to a maximum of the amount of ions being formed at an electron source filament current.

### Claim 7 (depends on 1)

The method of claim 1, wherein measuring parameters of the ion trap includes measuring an ion initial potential energy distribution (IPED) within the trap at a specified pressure of a test gas.

### Claim 8 (depends on 7)

The method of claim 7, wherein measuring the IPED includes measuring an IPED onset value.

### Claim 9 (depends on 7)

The method of claim 7, wherein the trap further includes an ion exit gate having an ion exit gate potential bias, and wherein adjusting ion trap settings further includes providing relative adjustment between the ion initial potential energy distribution (IPED) and the ion exit gate potential bias.

### Claim 10 (depends on 9)

The method of claim 9, wherein providing relative adjustment between the IPED and the ion exit gate potential bias includes setting the ion exit gate potential bias based on an IPED onset value.

### Claim 11 (depends on 10)

The method of claim 10, wherein providing relative adjustment between the IPED onset value and the ion exit gate potential bias further includes setting an electron multiplier shield potential bias based on the IPED onset value.

### Claim 12 (depends on 9)

The method of claim 9, wherein providing relative adjustment between the IPED and the ion exit gate potential bias includes adjusting an electron source repeller potential bias and an electron source filament bias to yield a specified IPED onset value.

### Claim 13 (depends on 1)

The method of claim 1, wherein measuring parameters of the ion trap includes measuring a minimum amount of applied RF excitation required to detect an ion signal of a specific ion mass.

### Claim 14 (depends on 13)

The method of claim 13, further including setting the RF excitation to an operational RF excitation setting that yields a specified peak ratio.

### Claim 15 (depends on 13)

The method of claim 13, wherein measuring parameters of the ion trap further includes measuring the ion signal as a function of applied RF excitation.

### Claim 16 (depends on 1)

The method of claim 1, wherein measuring parameters of the ion trap includes measuring an ion initial potential energy distribution (IPED) onset value and measuring an ion excited potential energy distribution (EPED) onset value at a test RF excitation setting.

### Claim 17 (depends on 16)

The method of claim 16, further including setting the test RF excitation setting to an operational RF excitation setting that yields a specified difference between the EPED and IPED onset values.

### Claim 18 (depends on 16)

The method of claim 16, further including setting the test RF excitation setting to an operational RF excitation setting that yields a specified spectral resolution.

### Claim 19 (depends on 16)

The method of claim 16, further including setting the test RF excitation setting to an operational RF excitation setting that yields a specified dynamic range.

### Claim 20 (depends on 16)

The method of claim 16, further including setting the test RF excitation setting to an operational RF excitation setting that yields a specified peak ratio of specified peaks in test spectra.

### Claim 21

An apparatus comprising:
i) an electrostatic ion trap, the trap including an ion source having an electron source; and
ii) electronics configured to measure parameters of the ion trap and configured to adjust ion trap settings based on the measured parameters and configured to employ the ion trap settings to produce test spectra from a test gas at a specified pressure.

### Claim 22 (depends on 21)

The apparatus of claim 21, wherein the electron source includes:
an entry slit assembly, including an entry plate having an entry plate potential bias;
a filament; and
a repeller that forms a beam of electrons from the filament and directs the electrons through the entry slit, the repeller having an extension located between the filament and the entry plate, the repeller shielding the filament from the entry plate potential.

### Claim 23 (depends on 21)

The apparatus of claim 21, wherein the electron source includes an entry slit assembly having an electrostatic lens located between the filament and the entry slit, the electrostatic lens collimating an electron beam from the filament through the entry slit.

### Claim 24 (depends on 21)

The apparatus of claim 21, wherein the electron source includes a unified electron source and entry slit assembly.

### Claim 25 (depends on 21)

The apparatus of claim 21, wherein adjusting ion trap settings includes adjusting electron source settings.

### Claim 26 (depends on 21)

The apparatus of claim 21, wherein the electronics are further configured to measure an amount of ions being formed by collisions between electrons and a specified pressure of a test gas and further configured to adjust electron source settings to increase the amount of ions being formed at an electron source filament current.

### Claim 27 (depends on 26)

The apparatus of claim 26, wherein increasing the amount of ions being formed includes increasing the amount of ions to a maximum of the amount of ions being formed at an electron source filament current.

### Claim 28 (depends on 26)

The apparatus of claim 26, wherein the electronics are further configured to set an electron source repeller potential bias to a setting that yields a maximum baseline ion current at an electron source filament current.

### Claim 29 (depends on 21)

The apparatus of claim 21, wherein the trap further includes an ion exit gate having an ion exit gate potential bias, and wherein the electronics are further configured to provide a relative adjustment between an ion initial potential energy distribution (IPED) and the ion exit gate potential bias.

### Claim 30 (depends on 29)

The apparatus of claim 29, wherein providing relative adjustment between the IPED and the ion exit gate potential bias includes setting the ion exit gate potential bias based on an IPED onset value.

### Claim 31 (depends on 30)

The apparatus of claim 30, wherein providing relative adjustment between the IPED and the ion exit gate potential bias further includes setting an electron multiplier shield potential bias based on the IPED onset value.

### Claim 32 (depends on 29)

The apparatus of claim 29, wherein providing relative adjustment between the IPED and the ion exit gate potential bias includes measuring an IPED onset value and adjusting an electron source repeller potential bias and an filament bias to yield a specified IPED onset value.

### Claim 33 (depends on 21)

The apparatus of claim 21, wherein the electronics are further configured to measure a minimum amount of applied RF excitation required to detect an ion signal of a specific ion mass.

### Claim 34 (depends on 33)

The apparatus of claim 33, wherein the electronics are further configured to set the RF excitation to an operational RF excitation setting that yields a specified peak ratio.

### Claim 35 (depends on 33)

The apparatus of claim 33, wherein the electronics are further configured to measure the ion signal as a function of applied RF excitation.

### Claim 36 (depends on 21)

The apparatus of claim 21, wherein measuring parameters of the ion trap includes measuring an ion initial potential energy distribution (IPED) onset value and an ion excited potential energy distribution (EPED) onset value at a test RF excitation setting.

### Claim 37 (depends on 36)

The apparatus of claim 36, wherein the electronics are further configured to set the test RF excitation setting to an operational RF excitation setting that yields a specified difference between the EPED and IPED onset values.

### Claim 38 (depends on 36)

The apparatus of claim 36, wherein the electronics are further configured to set the test RF excitation setting to an operational RF excitation setting that yields a specified spectral resolution.

### Claim 39 (depends on 36)

The apparatus of claim 36, wherein the electronics are further configured to set the test RF excitation setting to an operational RF excitation setting that yields a specified dynamic range.

### Claim 40 (depends on 36)

The apparatus of claim 36, wherein the electronics are further configured to set the test RF excitation setting to an operational RF excitation setting that yields a specified peak ratio of specified peaks in test spectra.