Method of operating a secondary-electron multiplier in the ion detector of a mass spectrometer

Patent metadata

Field	Value
Publication number	US-11049705-B2
Application number	US-201916359491-A
Country	US
Kind code	B2
Filing date	Mar 20, 2019
Priority date	Mar 29, 2018
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

The disclosure relates to a method of operating a secondary-electron multiplier in the ion detector of a mass spectrometer so as to prolong the service life, wherein the secondary-electron multiplier is supplied with an operating voltage in such a way that an amplification of less than 106 secondary electrons per impinging ion results, while the output current of the secondary-electron multiplier is amplified using an electronic preamplifier mounted close to the secondary-electron multiplier with such a low noise level that the current pulses of individual ions impinging on the ion detector are detected above the noise at the input of a digitizing unit. Further disclosed are the use of the methods for imaging mass spectrometric analysis of a thin tissue section or mass spectrometric high-throughput analysis/massive-parallel analysis, and a time-of-flight mass spectrometer whose control unit is programmed to execute such methods.

First claim

The invention claimed is:

1. A method to operate a secondary-electron multiplier having dynodes in an ion detector of a mass spectrometer in order to prolong the service life, comprising: —supplying the secondary-electron multiplier with an operating voltage in such a way that an amplification of less than 10 5 secondary electrons per impinging ion results, and—amplifying an output current of the secondary-electron multiplier using an electronic pre-amplifier mounted in a vacuum system of the mass spectrometer in which the secondary-electron multiplier is located, or on a housing of said vacuum system, wherein a pre-amplifier amplification is chosen such that a resultant noise level allows current pulses generated by individual ions impinging on the ion detector to be detected above the noise at an input of a digitizing unit.

2. The method according to claim 1 , wherein the amplification of the secondary-electron multiplier is set to a maximum of 2×10 4 secondary electrons per impinging ion.

3. The method according to claim 1 , wherein the preamplifier is flange-mounted on the housing of the vacuum system.

4. The method according to claim 1 , wherein operation of the preamplifier is improved by cooling the preamplifier.

5. The method according to claim 1 , wherein improved amplification is achieved by mounting the preamplifier less than 40 centimeters from the secondary-electron multiplier.

6. The method according to claim 1 , wherein an adjustment of the amplification is implemented via the acquisition of a mass spectrum with individual ion signals at specific times of the operation of the secondary-electron multiplier.

7. The method according to claim 6 , wherein the desired amplification of the secondary-electron multiplier is set via a characteristic curve which reflects the logarithm of the amplification as a function of the operating voltage.

8. The method according to claim 7 , wherein two different operating voltages are used to determine the gradient of the characteristic curve and to adjust the amplification.

9. A time-of-flight mass spectrometer whose control unit is programmed to execute a method according to claim 1 .

10. A method to operate a secondary-electron multiplier having dynodes in an ion detector of a mass spectrometer in order to prolong the service life, during an imaging mass spectrometric analysis of a thin tissue section or a mass spectrometric high-throughput analysis/massive-parallel analysis, comprising: —supplying the secondary-electron multiplier with an operating voltage in such a way that an amplification of less than 10 5 secondary electrons per impinging ion results, and—amplifying an output current of the secondary-electron multiplier using an electronic pre-amplifier mounted in a vacuum system of the mass spectrometer in which the secondary-electron multiplier is located, or on a housing of said vacuum system, wherein a pre-amplifier amplification is chosen such that a resultant noise level allows current pulses generated by individual ions impinging on the ion detector to be detected above the noise at an input of a digitizing unit.

Assignees

• Bruker Daltonik Gmbh

Inventors

• Böhm Sebastian
• Haase Andreas
• Höhndorf Jens

Classifications

• H01J49/025 Primary

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

• H01J49/40

  Time-of-flight spectrometers (H01J49/36 takes precedence) · CPC title

• H01J49/0031

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title

• H01J49/08

  Electron sources, e.g. for generating photo-electrons, secondary electrons or Auger electrons · CPC title

• H01J49/022 Primary

  Circuit arrangements, e.g. for generating deviation currents or voltages (regulating electric or magnetic variables in general, e.g. current, magnetic field G05F); Components associated with high voltage supply (high voltage supply per se H02M) · CPC title