Mass spectrometer for detecting leaks via a tracer gas

Abstract

The present invention relates to a mass spectrometer (10) for detecting leaks via tracer gas, the mass spectrometer (10) comprising: an ionization component (3) for ionizing the tracer gas; at least one magnetic field source (501) generating a magnetic field (I) dependent on a current I supplied to the source (501) and intended to sort ionized elements; a component (7) for detecting the ionized tracer gas; characterized in that the mass spectrometer includes a component (II) for adjusting the magnetic field, the adjusting component being configured to allow at least two separate adjustments having different sensitivities.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometers, and more specifically, to the detection of leaks by tracer gas mass spectrometry. Background Technology

[0002] It should be noted that a mass spectrometer is a device that uses the movement of ions in an electric and / or magnetic field to classify them according to their mass / charge ratio. For example... Figure 1 As shown, a mass spectrometer 1 typically includes an ionization component 3, an analyzer 5, and a detection component 7.

[0003] The ionization component 3 is configured to ionize one or more chemical elements to be analyzed. This ionization also produces ions that will subsequently be sorted and selected according to their mass / charge ratio.

[0004] This sorting can be achieved in various ways, but more specifically, the focus here is on the selection made at least by means of a magnetic field to disperse ions.

[0005] The sorted ions are then sent to a detection element 7, such as a detector that converts the received ion stream into an electric current. The current output from the detector then undergoes signal processing, making it possible to obtain more accurate measurements related to the ions.

[0006] This type of mass spectrometer can be specifically used to detect leaks or monitor the airtightness of objects, for example, by measuring and quantifying tracer gases such as helium or dihydrogen. However, other types of tracer gases, such as dihydrogen or carbon dioxide, can also be used.

[0007] However, mass spectrometers used for leak detection are designed for industrial environments where many environmental factors can interfere with measurements or settings, specifically temperature changes, vibrations, movement, equipment maintenance, etc.

[0008] In addition, the mass spectrometer used to detect leaks must be as versatile as possible, specifically, to operate with a variety of tracer gases, to adapt, for example, to the available tracer gases and / or the level of leak sought. Summary of the Invention

[0009] The present invention thus makes it possible to remedy one or more of the problems mentioned above by providing a mass spectrometer for detecting leaks by tracer gas, said mass spectrometer comprising:

[0010] - An ionization component designed to ionize the tracer gas;

[0011] - At least one magnetic field source that generates a magnetic field designed for sorting ionized elements. The magnetic field depends on the current I supplied to the magnetic field source;

[0012] - A component for detecting the ionized tracer gas.

[0013] According to the present invention, the mass spectrometer includes a function for adjusting the magnetic field generated by the magnetic field source. The adjustment component is configured to allow at least two dissimilar adjustments with different sensitivities.

[0014] Depending on the possible features, the adjustment element includes pre-adjustment (or coarse adjustment) and fine adjustment.

[0015] According to another possible feature, one of the adjustments makes it possible to establish a nominal magnetic field. Another adjustment enables the generation of the nominal magnetic field. Magnetic field changes near the value

[0016] Electromagnetic field generated by magnetic field source Therefore, in this case, it is the nominal magnetic field. and magnetic field changes sum.

[0017] According to another possible feature, the magnetic field source includes an electromagnet.

[0018] It should be noted that the magnetic field source may also be a magnetic sector incorporating one or more electromagnets.

[0019] According to another possible feature, the regulating member includes at least two regulating commands, a combination circuit configured to combine the values ​​of the at least two commands, and a circuit for controlling the current I circulating in the magnetic field source.

[0020] According to another possible feature, the at least two regulation commands are electrical quantities, such as voltage.

[0021] According to another possible characteristic, the magnetic field The value of the electrical quantity depends on the values ​​of the at least two adjustment commands.

[0022] According to another possible feature, the mass spectrometer includes N adjustment commands and / or N magnetic field sources, where N is an integer greater than or equal to 3.

[0023] Multiple adjustment commands and / or magnetic field sources make it possible to handle a large number of tracer gases and facilitate the adjustment of the mass spectrometer according to the invention.

[0024] According to another possible feature, the combined circuit includes:

[0025] - Multiple resistors R1, R2, R3 and R4;

[0026] - Operational amplifier AO1, which is associated with resistors R1, R2, R3 and R4 to form a non-inverting summing circuit.

[0027] According to another possible feature, the control circuit includes a grounding resistor R S An operational amplifier AO2 associated with transistor T1 forms a voltage-to-current converter type circuit.

[0028] The present invention also relates to a system for detecting leaks via tracer gas, characterized in that the system comprises a mass spectrometer as defined above. Attached Figure Description

[0029] The invention will be better understood, and other objects, details, features, and advantages of the invention will become more apparent in the following description of specific embodiments thereof, with reference to the accompanying drawings, which are given for illustrative purposes only and not for limiting purposes, wherein:

[0030] -marked as [ Figure 1 ]of Figure 1 It is a highly schematic representation of the mass spectrometer and its main functional components;

[0031] -marked as [ Figure 2 ]of Figure 2 This is a highly schematic representation of an example of a circuit used to monitor the airtightness of an object by means of a tracer gas and a mass spectrometer according to the invention;

[0032] -marked as [ Figure 3 ]of Figure 3 yes Figure 2 A magnified schematic representation of a mass spectrometer;

[0033] -marked as [ Figure 4 ]of Figure 4 It is used for regulation Figure 2 A schematic diagram of the components of the magnetic field source of a mass spectrometer. Detailed Implementation

[0034] [ Figure 2 [This is a highly schematic representation of an example of a leak detection system 100 via a tracer gas, including a mass spectrometer 10 according to the invention. It should be noted that the mass spectrometer 10 includes...] Figure 1 The same functional parts as the mass spectrometer 1, and therefore the same or similar components will be labeled with the same designation and will not be described in detail.

[0035] The system 100 therefore includes:

[0036] - Test chamber 101, which is configured to contain the object whose airtightness will be tested;

[0037] - Leakage detection device 102, which is connected to test chamber 101 and includes mass spectrometer 10, main vacuum pump 107 and auxiliary vacuum pump 109;

[0038] - Gas source 103, which is connected to the object and configured to fill the object with a tracer gas such as hydrogen or helium.

[0039] For example, the main vacuum pump 107 of the turbomolecular pump has an inlet connected to the test chamber 101, but is also connected to the mass spectrometer 10. The auxiliary vacuum pump 109 is itself connected to the outlet of the main vacuum pump 107.

[0040] The system 100 also includes multiple valves 111 and 113:

[0041] - A first valve 111 is disposed on a pipe that connects a gas source 103 to the object being tested, the object itself being disposed in a test chamber 101, the valve 111 making it possible to adjust the amount of tracer gas injected into the object being tested;

[0042] - A second valve 113 is located on the pipe that connects the test chamber 101 to the main vacuum pump 107.

[0043] The main pump 107 generates a high vacuum, which is used to evacuate the tracer gas that has been introduced into the test chamber 101 due to leakage from the test object. Subsequently, within the main pump 107, the tracer gas flows primarily in the direction of the auxiliary pump 109, but some of the tracer gas moves into the mass spectrometer 10 for analysis.

[0044] The main vacuum pump 107 is, for example, a turbomolecular pump, a diffusion pump, or any other type of molecular pump, making it possible to achieve a detection order of at least 10 -3 Leakage-compatible vacuum level in mbar.L / sec.

[0045] like Figure 3 As shown, the mass spectrometer 10 therefore includes an ionization component 3, which includes, for example, an ion source 301 having a cathode 301a and an anode 301b. The ion source 301 is surrounded by a sieve in which openings (or diaphragms) are formed, thereby enabling the ion beam F to be emitted toward the analyzer 5.

[0046] Analyzer 5 itself is configured to select relevant ions, specifically by means of a magnetic field. This occurs because the analyzer 5 specifically includes a magnetic field source 501, which is configured to generate a plane orthogonal to the path of the ions (i.e., orthogonal to...). Figure 3 A magnetic field (a plane capable of bending the path of ions)

[0047] Magnetic field source 501 is more specifically a source whose magnetic field depends on the current "supplying" the source.

[0048] Therefore, the magnetic field source 501 is, for example, an electromagnet, i.e., a ferromagnetic material on which windings are disposed, and the magnetic field generated depends on the current circulating in the windings (specifically, the direction and intensity of the circulation). It should be noted that the source 501 can also be, for example, a magnetic sector.

[0049] Therefore, in the magnetic field In the presence of [a specific force / mechanism], the ion beam F is redirected. This is due to the Lorentz force and the uniform magnetic field in the plane perpendicular to the ion's path. The ion will be given a curved path (the point of impact of the ion, and thus its deviation, making it possible to know its mass from its charge).

[0050] Due to magnetic field The redirected ion beam F is then oriented toward one or more diaphragms, with the detection element 7 positioned behind the diaphragm.

[0051] The detection component 7 includes, for example, one or more sensors 703 and / or 705 and electronic circuitry 701 connected to the sensors 703 and 705 to process electrical signals from them.

[0052] It should be noted that the mass spectrometer 10 may also include the following components (not shown): one or more electrostatic lenses, accelerator plates, etc., for coupling, focusing, collection, etc. These components may be located at the ionization source 3, the analyzer 5, or the detection component 7, or between said components 3, 5, and 7.

[0053] Therefore, when adjusting the magnetic field in analyzer 5 In order to accurately determine the presence of a tracer gas of a defined mass M in the middle of at least one diaphragm 501a or 501b (acting as a selector), other gases with the same charge but different masses than M will deflect at different radii in analyzer 4. Gases with masses less than M will deflect at smaller radii, while gases with masses greater than M will deflect at radii larger than those associated with the gas of mass M.

[0054] In order to allow magnetic fields The mass spectrometer 10 includes a component 400 for adjusting the magnetic field generated by the source 501, for example, by the electromagnet. This component... Figure 4 More specifically shown in the text.

[0055] in this way Figure 4 As described above, the adjusting member 401 is connected to the coil of the electromagnet 501 and is configured to change the intensity of the current I circulating in the coil.

[0056] The regulating component 401 therefore includes two distinct regulating commands 401 and 403, a circuit 405 for controlling the current of the electromagnet 501, and a combined circuit 407 for the commands 401 and 403. The combined circuit 407 is configured to receive the commands 401 and 403 as inputs and thus produce a function F as output that depends on the values ​​of the commands 401 and 403.

[0057] The resulting function F is then sent to the control circuit 405, causing the current I to be adjusted according to the values ​​of the commands 401 and 403.

[0058] The commands 401 and 403 are, for example, digital-to-analog converters that deliver voltages V1 and V2 as inputs to the combinational circuit 407, respectively. However, it should be noted that any electrical quantity can be adapted with appropriate arrangement.

[0059] Specifically, the combined circuit 407 includes:

[0060] - Multiple resistors R1, R2, R3 and R4;

[0061] - Operational amplifier AO1, which is associated with resistors R1, R2, R3 and R4 to form a non-inverting summing circuit.

[0062] Therefore, the combined circuit 407 will have a voltage V at its output that depends on the input voltage values ​​V1 and V2 and the resistors R1, R2, R3 and R4, of the following type. S :

[0063]

[0064] By reasonably selecting the values ​​of the resistors R1, R2, R3, and R4, for example by taking R1 = R3 = R4 = R and R2 = kR, where k is a constant greater than 1 and preferably much larger than 1, the function F is simplified to:

[0065]

[0066] The two commands V1 and V2 will therefore have different weights, and will thus significantly affect the output voltage V. S The value of . It should be noted that voltage V2 affects the output voltage V. S The effect is K times the effect of voltage V1.

[0067] The control circuit 405 itself includes a grounding resistor R. SAn operational amplifier AO2, associated with transistor T1, forms a voltage-to-current (or transconductance) converter type circuit. Transistor T1 is, for example, a bipolar transistor (or MOSFET type), with its base (or gate) connected to the output of operational amplifier AO2, its collector (or source) connected to electromagnet 501, and its emitter (or drain) connected to resistor R. S .

[0068] Output voltage V from combinational circuit 407 S The input sent to the inverting input of operational amplifier AO2, and the non-inverting input connected to the ground resistor R, are both connected to the inverting input. S and the emitter of transistor T1 (more specifically, connected to the resistor R located at the emitter of transistor T1 and ground). S (nodes between).

[0069] Output voltage V' from operational amplifier AO2 S Therefore, the value of the current I circulating through transistor T1 and electromagnet 501 is adjusted. According to the following formula, the current I depends on the voltages V1 and V2 of commands 401 and 403:

[0070]

[0071] magnetic field Therefore, it depends (more specifically, proportional to the electromagnet) on the strength of the current I circulating in the coil of electromagnet 501, and thus the field This depends on commands 401 and 403.

[0072] The current I circulating in the electromagnet 501 can also be defined as follows:

[0073] I = I0 + ΔI

[0074] Where I0 is the nominal current that depends on voltage V1, and it generates a nominal magnetic field. Furthermore, ΔI depends on the small current change of V2 near the nominal current I0, which generates the nominal magnetic field. Magnetic field changes near the value

[0075] Therefore, one of the adjustment commands, 401, makes it possible to establish a nominal magnetic field. Another adjustment command makes it possible to generate a nominal magnetic field. Magnetic field changes near the value

[0076] Alternatively, the adjustment component 400 may be defined as including an adjustment command 401 equivalent to pre-adjustment (or coarse adjustment), while the adjustment command 403 is fine adjustment.

Claims

1. A mass spectrometer (10) for detecting leaks via tracer gas, said mass spectrometer (10) comprising: -Ionization component (3), which is designed to ionize the tracer gas; - At least one magnetic field source (501) that generates a magnetic field designed to sort ionized elements. The magnetic field depends on the current I supplied to the magnetic field source (501); - Detection component (7) for detecting the ionized tracer gas; The mass spectrometer is characterized in that it includes a function for adjusting the magnetic field generated by the magnetic field source (501). The adjustment member (400) is configured to allow at least two dissimilar adjustments with different sensitivities. The regulating component includes at least two regulating commands (401 and 403), a combination circuit (407) configured to combine the values ​​of the at least two regulating commands (401 and 403), and a control circuit (405) for controlling the current I circulating in the magnetic field source (501).

2. The mass spectrometer according to claim 1, characterized in that, The adjustment components include pre-adjustment and fine adjustment.

3. The mass spectrometer according to claim 1, characterized in that, One of the adjustments allows a nominal magnetic field to be established. Another adjustment allows the generation of the nominal magnetic field. Magnetic field changes near the value .

4. The mass spectrometer according to claim 1, characterized in that, The magnetic field source (501) includes an electromagnet.

5. The mass spectrometer according to claim 1, characterized in that, The at least two adjustment commands are electrical quantities V1 and V2.

6. The mass spectrometer according to claim 5, characterized in that, The electrical quantities V1 and V2 are voltages.

7. The mass spectrometer according to claim 5, characterized in that, The magnetic field The values ​​of the electrical quantities V1 and V2 depend on the at least two adjustment commands.

8. The mass spectrometer according to claim 1, characterized in that, The combined circuit (407) includes: - Multiple resistors R1, R2, R3 and R4; - Operational amplifier AO1, which is associated with resistors R1, R2, R3 and R4 to form a non-inverting summing circuit.

9. The mass spectrometer according to claim 1, characterized in that, The control circuit (405) includes a grounding resistor (R). S An operational amplifier AO2 associated with a transistor (T1) and an operational amplifier AO2 are combined to form a voltage-to-current converter type circuit.

10. The mass spectrometer according to claim 1, characterized in that, The mass spectrometer includes N adjustment commands and / or N magnetic field sources, where N is an integer greater than or equal to 3.

11. A system for detecting leaks via tracer gas, characterized in that, The system includes a mass spectrometer (10) according to any one of the preceding claims.

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