Method for following degassing rate by measuring partial pressures measured by mass spectrometry

Patent metadata

Field	Value
Publication number	US-9903801-B2
Application number	US-201414473457-A
Country	US
Kind code	B2
Filing date	Aug 29, 2014
Priority date	Aug 30, 2013
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

A method for following the degassing of a component placed in a vacuum chamber, comprises: measuring partial pressures P i for a set M of reference atomic masses, by means of a mass spectrometer connected to the vacuum chamber; determining a degassing rate η, at least as a function of the measured partial pressures P i ; and, calculating a slope of the variation in the degassing rate. The degassing rate η may advantageously be determined by calculation by means of a relationship of the type:
η = ∑ i ∈ M ⁢ ⁢ α i ⁢ P i ∑ i = 0 N ⁢ ⁢ α i ⁢ P i ⁢
where M denotes the set of reference atomic masses, P i denotes the partial pressures for the atomic masses measured by the mass spectrometer, the coefficients α i denote preset weighting coefficients associated with each partial pressure P i , and N denotes a maximum atomic mass for which the partial pressure P i can be measured by the mass spectrometer.

First claim

The invention claimed is:

1. A method of degassing a component, the method comprising:
placing the component in a vacuum chamber;
reducing a pressure in the vacuum chamber by pumping air out of the vacuum chamber;
periodically measuring, with a mass spectrometer, partial pressures P i for a set M of reference atomic masses, the mass spectrometer being connected to the vacuum chamber;
periodically determining a degassing rate η, at least as a function of the partial pressures P i measured for the set M of reference atomic masses, by calculating:

η
=

∑

i
∈
M

⁢

⁢

α
i

⁢

P
i

∑

i
=
0

N

⁢

⁢

α
i

⁢

P
i

⁢

wherein M denotes the set of reference atomic masses, P i denotes the partial pressures for the atomic masses measured by the mass spectrometer, coefficients α i denote preset weighting coefficients associated with each partial pressure P i , and N denotes a maximum atomic mass for which the partial pressure P i can be measured by the mass spectrometer; and
controlling the degassing as a function of at least one of said degassing rate η and a variation in the degassing rate η.

2. The method according to claim 1 , wherein the set M includes at least the following atomic masses: 16, 18, 30, 32 and 44.

3. The method according to claim 1 , further comprising selecting the set M from a preset list of reference atomic masses prior to calculating the degassing rate.

4. The method according to claim 1 , further comprising selecting the weighting coefficients α i from a preset list of weighting coefficients.

5. The method according to claim 1 , wherein the weighting coefficients α i are all equal to 1.

6. The method according to claim 1 , further comprising
periodically determining a stopping criterion as a function of at least a slope of the variation in the degassing rate η.

7. The method according to claim 6 , wherein the stopping criterion is determined at least by comparing the slope of the variation in the degassing rate η with a preset value.

8. The method according to claim 6 , wherein the stopping criterion is determined at least by comparing a ratio of the determined slope of the variation in the degassing rate to a predetermined slope of the variation in the degassing rate η o .

9. The method according to claim 6 , wherein the stopping criterion is determined as a function of the slope of the variation in the degassing rate η and a ratio of the determined slope of the variation in the degassing rate to an initially determined slope of the variation in the degassing rate η o .

10. The method according to claim 1 , further comprising generating an alert to an operator based on the degassing rate η or the slope of the variation in the degassing rate.

11. A mass spectrometer comprising a control module configured to implement the method according to claim 1 .

12. A degassing device comprising:
a vacuum chamber configured to degas a component; and
a mass spectrometer according to claim 11 .

13. The method according to claim 1 , wherein controlling the degassing comprises modifying a temperature and the pressure in the vacuum chamber.

14. The method according to claim 1 , further comprising periodically calculating and displaying, on a screen, a slope of the variation in the degassing rate η.

15. The method according to claim 1 , further comprising:
periodically calculating a slope of the variation in the degassing rate η;
periodically determining a stopping criterion as a function of said slope of the variation in the degassing rate η; and
alerting an operator based on the stopping criterion.

Assignees

• Thales Sa

Inventors

• Bettacchioli Alain Roger Dante

Classifications

• G01N7/14 Primary

  by allowing the material to emit a gas or vapour, e.g. water vapour, and measuring a pressure or volume difference {(determining urea G01N33/48742)} · CPC title

• H01J49/26

  Mass spectrometers or separator tubes · CPC title

• H01J49/0036

  Step by step routines describing the handling of the data generated during a measurement · CPC title