Quadrupole mass spectrometer and vacuum device using the same

• US 7,332,714 B2
• Filed: 03/15/2006
• Issued: 02/19/2008
• Est. Priority Date: 03/23/2005
• Status: Expired due to Fees

• Current Assignee: VacLab Inc.
• Original Assignee: VacLab Inc.
• Inventors: Watanabe, Fumio, Watanabe, Reiki
• Primary Examiner(s): Wells; Nikita
• Application Number:
  US11/375,063
• Publication Number:
  US 20060226355A1
• Time in Patent Office: 706 Days
• Field of Search: None
• US Class Current: 250/283
• CPC Class Codes: H01J 41/10 of particle spectrometer type particle spectrometers per se H01J49/00
• CPC Class Codes: H01J 49/147 with electrons, e.g. electron impact ionisation, electron attachment H01J49/145 takes precedence
• CPC Class Codes: H01J 49/4215 Quadrupole mass filters H01J49/4225 takes precedence

Abstract

In a quadrupole mass spectrometer which measures partial pressure strength according to a gas type in a vacuum system from ion current intensity, a quadrupole mass spectrometer with a total pressure measurement electrode has a total pressure measurement electrode for examining an ion density disposed in a demarcation space which is comprised of a grid electrode and an ion focusing electrode. And, a vacuum system is provided with only the quadrupole mass spectrometer which measures partial pressure strength according to a gas type in the vacuum system from an ion current intensity and does not have an ionization vacuum gauge other than the quadrupole mass spectrometer.

Claims

1. A quadrupole mass spectrometer, comprising:

an electron impact ion source in which a demarcation space is formed of at least a grid electrode and an ion focusing electrode within a vacuum system, electrons emitted from an electron emitter which is disposed outside of the grid electrode are accelerated toward the grid electrode, gas molecules flying into the demarcation space are ionized in a process that the accelerated electrons pass through the mesh of the grid electrode and then continue to oscillate to inside and outside of the grid electrode, and the ionized ions are emitted as an ion beam to outside of the demarcation space through a hole formed in the center of the ion focusing electrode;

a quadrupole mass analyzing portion which separates the ion beam obtained from the ion source depending on a charge-to-mass ratio of the ions;

a detector which catches an ion beam according to the mass separated through the quadrupole mass analyzing portion and converts it into an electric current signal; and

a total pressure measurement electrode for examining an ion density disposed in the demarcation space which is formed of the grid electrode and the ion focusing electrode, wherein;

partial pressure strength according to a gas type in the vacuum system is measured from an ion current intensity to be obtained.

2. The quadrupole mass spectrometer according to claim 1, wherein the total pressure measurement electrode has one end of a wire inserted into the demarcation space through a hole formed in the grid electrode or the mesh of the grid electrode.

3. The quadrupole mass spectrometer according to claim 1, wherein the total pressure measurement electrode is provided with an electrical lead held outside of the grid electrode, and the electrical lead is electrically shielded to prevent ions generated outside of the grid electrode from entering.

4. The quadrupole mass spectrometer according to claim 1, wherein the total pressure measurement electrode is connected to an insulation vacuum terminal, which is disposed on the wall of a vacuum vessel of the vacuum system, through the electrical lead, and the other end of the insulation vacuum terminal is connected to an electrometer, which is held at a ground potential, in the atmosphere.

5. The quadrupole mass spectrometer according to claim 4, wherein the total pressure measurement electrode is connected to the insulation vacuum terminal, which is disposed on the wall of the vacuum vessel of the vacuum system, through the electrical lead, and the other end of the insulation vacuum terminal can select either of electric potential of an electrical lead for supplying the grid electrode with voltage or the electrometer held at the ground potential by switching an electric contact switch on the atmosphere side.

6. A quadrupole mass spectrometer, comprising:

an electron impact ion source in which a demarcation space is formed of at least a grid electrode and an ion focusing electrode within a vacuum system, electrons emitted from an electron emitter which is disposed outside of the grid electrode are accelerated toward the grid electrode, gas molecules flying into the demarcation space are ionized by the accelerated electrons which have passed through the grid electrode and then continue to oscillate to inside and outside of the grid electrode, and the ionized ions are taken out as an ion beam to outside of the demarcation space through a hole formed in the center of the ion focusing electrode;

a quadrupole mass analyzing portion which separates the ion beam obtained from the ion source depending on a charge-to-mass ratio of the ions; and

a detector which catches an ion beam according to the mass separated through the mass analyzing portion and converts it into an electric current signal, wherein;

total pressure measurement in the demarcation space which is formed of the grid electrode and the ion focusing electrode is performed by means having disposed a total pressure measuring electrode, which has a hole smaller than the diameter of the hole formed in the center of the ion focusing electrode, between the ion focusing electrode and the quadrupoles outside of the demarcation space;

the total pressure measuring electrode is electrically insulated and mounted by screw bolts which are held at a ground potential but not in contact with an insulator which is in contact with a positive electric potential; and

partial pressure strength according to a gas type in the vacuum device is measured from a strength of the ion current to be obtained.

7. A vacuum system, comprising:

means which has a demarcation space formed of at least a grid electrode and an ion focusing electrode and measures a molecular density of residual gas molecules in the vacuum system;

an electron impact ion source in which a total pressure measurement electrode for examining an ion density is disposed within the demarcation space which is formed of the grid electrode and the ion focusing electrode to accelerate electrons emitted from an electron emitter which is disposed outside of the grid electrode toward the grid electrode, to ionize gas molecules flying into the demarcation space in a process that the accelerated electrons continue to oscillate in and out of the grid electrode and to emit the ionized ions as an ion beam to outside of the demarcation space through a hole formed in the center of the ion focusing electrode;

a quadrupole mass analyzing portion which separates the ion beam obtained from the ion source depending on a charge-to-mass ratio of the ions; and

a detector which catches an ion beam according to the mass separated through the quadrupole mass analyzing portion and converts it into an electric current signal, wherein;

only a quadrupole mass spectrometer which measures a partial pressure strength according to a gas type in the vacuum system from an ion current intensity to be obtained is mounted, and an ionization vacuum gauge other than the quadrupole mass spectrometer is not provided.