Gas analysis with an inverted magnetron source

Patent metadata

Field	Value
Publication number	US-10928265-B2
Application number	US-201916397436-A
Country	US
Kind code	B2
Filing date	Apr 29, 2019
Priority date	May 29, 2018
Publication date	Feb 23, 2021
Grant date	Feb 23, 2021

Abstract

A total pressure cold cathode ionization gauge is disclosed. An inverted magnetron electrode design is capable of simultaneously detecting and measuring total gas pressure in a high vacuum system, along with partial pressures of one or more gases, such as hydrogen, helium and water. In addition, a leak detector, such as a helium leak detector, is disclosed with a compact counterflow arrangement of a gas inlet passage to an ion detection passage.

First claim

What is claimed is:

1. An inverted magnetron cold cathode ionization vacuum gauge comprising:
an anode electrode;
a cathode electrode assembly surrounding a length of the anode electrode and positioned to create an electric field in a discharge space between the cathode electrode assembly and the anode electrode;
a magnet assembly positioned to define a magnetic field across the electric field;
an opening in the cathode electrode assembly positioned to permit entry of a gas from a monitored chamber into the discharge space such that ions of the gas are formed in the discharge space to be accelerated by the electric field in a direction towards the cathode electrode assembly;
a source aperture in the cathode electrode assembly positioned to emit a portion of the ions of the gas out of the cathode electrode assembly;
the magnet assembly positioned to angularly displace the emitted portion of the ions based on a mass to charge ratio of ions of the gas;
a detector positioned to detect a displaced ion component of the emitted portion of the ions; and
ion current measurement circuitry electrically connected to measure a total current flowing between the anode electrode and the cathode electrode assembly, and electrically connected to measure a current produced from receipt of the displaced ion component at the detector.

2. The inverted magnetron cold cathode ionization vacuum gauge of claim 1 , further comprising:
a total pressure display, in electrical connection with the ion current measurement circuitry, comprising an indication of a total pressure of the gas from the monitored chamber; and
a partial pressure display, in electrical connection with the ion current measurement circuitry, comprising an indication of a partial pressure of a gas from the monitored chamber.

3. The inverted magnetron cold cathode ionization vacuum gauge of claim 1 , further comprising a gas inlet passage positioned to flow the gas from the monitored chamber to the opening in the cathode electrode assembly, wherein the emitted portion of the ions travel in a direction counter to the flow of the gas from the monitored chamber in the gas inlet passage.

4. The inverted magnetron cold cathode ionization vacuum gauge of claim 1 , further comprising an electrostatic shield grid positioned between the source aperture and the detector.

5. The inverted magnetron cold cathode ionization vacuum gauge of claim 1 , further comprising an energy filter grid positioned between the source aperture and the detector.

6. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , wherein the detector comprises:
an ion shield;
a detector aperture; and
a Faraday collector.

7. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , wherein the detector comprises an electron multiplier.

8. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising:
a power supply; and
a current limiting circuit electrically connected between the power supply and the anode electrode.

9. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , comprising an anode voltage control circuit configured to maintain a constant voltage of the anode electrode independent of the total current flowing between the anode electrode and the cathode electrode assembly.

10. The magnetron cold cathode ionization vacuum gauge of claim 5 , comprising an anode voltage control circuit configured to vary a voltage of the anode electrode based on the total current flowing between the anode electrode and the cathode electrode assembly.

11. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a magnetic field extension assembly positioned to extend the magnetic field outside the cathode electrode assembly.

12. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a high pass ion energy filter configured to permit only ions that have energies higher than a desired threshold energy to be detected.

13. The inverted magnetron cold cathode ionization vacuum gauge of claim 12 , wherein the high pass ion energy filter comprises a voltage source applying a bias voltage to the detector.

14. The inverted magnetron cold cathode ionization vacuum gauge of claim 12 , further comprising a voltage source configured to vary a bias voltage of the high pass ion energy filter based on a voltage of the anode electrode.

15. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a low pass ion energy filter configured to permit only ions that have energies lower than a desired threshold energy to be detected.

16. The inverted magnetron cold cathode ionization vacuum gauge of claim 15 , wherein the low pass ion energy filter comprises:
a voltage-biased deflector plate; and
a collector plate of the detector.

17. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , wherein the magnet assembly comprises a flat plate magnet positioned to define both the magnetic field across the electric field and an external magnetic field outside the cathode electrode assembly.

18. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a total pressure determination circuit configured to determine a total pressure of the gas from the monitored chamber based at least on a total current flowing between the anode electrode and the cathode electrode assembly.

19. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a quadrupole mass filter positioned between the source aperture and the detector.

20. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , wherein the displaced ion components comprise at least one of: helium ions, hydrogen ions, water ions, and residual gas ions.

21. The inverted magnetron cold cathode ionization vacuum gauge of claim 20 , wherein the displaced ion components comprise helium ions separated from other components of the gas from the monitored chamber.

22. The inverted magnetron cold cathode ionization vacuum gauge of claim 20 , wherein the displaced ion components comprise water ions separated from other components of the gas from the monitored chamber.

23. The inverted magnetron cold cathode ionization vacuum gauge of claim 20 , wherein the displaced ion components comprise both displaced helium ions and displaced water ions, each separated from each other and from other components of the gas from the monitored chamber.

24. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising a cathode rotation coupling.

25. The inverted magnetron cold cathode ionization vacuum gauge of claim 5 , further comprising an ion beam deflector positioned between the source aperture and the detector.

26. The inverted magnetron cold cathode ionization vacuum gauge of claim 25 , wherein the ion beam deflector comprises a pair of parallel plates.

27. The inverted magnetron cold cathode ionization vacuum gauge of claim 25 , wherein the ion beam deflector comprises a pair of curved plates.

28. The inverted magnetron cold cathode ionization vacuum gauge of claim 25 , further comprising a deflector power supply electrically connected to the ion beam deflector to create an electrostatic field between a pair of deflector plates of the ion beam d

Assignees

• Mks Instr Inc

Inventors

• Brucker Gerardo A
• Swinney Timothy C
• Percy Clinton L

Classifications

• H01J41/06 Primary

  with ionisation by means of cold cathodes · CPC title

• G01M3/205

  Accessories or associated equipment; Pump constructions · CPC title

• G01L21/34 Primary

  using electric discharge tubes with cold cathodes · CPC title

• G01M3/202

  using mass spectrometer detection systems · CPC title