MASS SPECTROMETER AND METHOD FOR ESTABLISHING VACUUM SYSTEM THEREOF

Abstract

The present invention provides a mass spectrometer and a method for establishing a vacuum system thereof, the mass spectrometer having a hermetical chamber in communication with an external environment only through a vacuum interface, the chamber comprising a first chamber and a second chamber, the second chamber having an adsorption pump disposed therein, the first chamber being in communication with the second chamber through a flow restricting structure. The present solution can be applied to bench-top and even portable mass spectrometers, taking into account the low energy consumption, miniaturization and vacuum requirements of such mass spectrometers.

Claims

1. A mass spectrometer characterized by comprising: a hermetical chamber communicated with external environment only through one or more vacuum interface, the chamber comprising a first chamber and a second chamber, an adsorption pump located in the second chamber, and a flow restricting structure through which the first chamber and the second chamber are communicated with each other.

2. The mass spectrometer of claim 1, characterized in that an ion trap is arranged in the first chamber, and the gas pressure range of the first chamber is P1≥10.sup.−2 Pa.

3. The mass spectrometer of claim 2, characterized in that a detector, a mass analyzer and/or an ion source are also disposed in the first chamber.

4. The mass spectrometer of claim 2, characterized in that the gas pressure of the second chamber is kept below activation gas pressure of the adsorption pump.

5. The mass spectrometer of claim 4, characterized in that the adsorption pump is a getter pump using alloy as getter material, and the gas pressure range of the second chamber is P2≤10.sup.−2 Pa.

6. The mass spectrometer of claim 1, characterized in that the vacuum interface comprises a vacuum pump interface communicated with the second chamber, and the second chamber communicates with the external vacuum pump via the vacuum pump interface, whereby the gas pressure of the second chamber is pre-pumped to a low-enough safe pressure for adsorption pump activation operation.

7. The mass spectrometer of claim 1, characterized in that the adsorption pump is a primary pump of the mass spectrometer.

8. The mass spectrometer of claim 1, characterized by further comprising a sample introducing means for introducing a sample into the first chamber.

9. The mass spectrometer of claim 8, characterized in that the sample introduction means is a gas chromatography sample introducing means, a capillary sample introducing means or a membrane sample introducing means.

10. The mass spectrometer of claim 9, characterized in that the carrier gas of the gas chromatography is hydrogen, helium or nitrogen.

11. The mass spectrometer of claim 9, characterized in that the sample introducing means further comprises a thermal desorption assembly.

12. The mass spectrometer of claim 1, characterized in that the mass spectrometer is a compact mass spectrometer.

13. The mass spectrometer of claim 1, characterized in that the flow restricting structure is a flow restricting aperture, a flow restricting valve or a flow restricting tube.

14. The mass spectrometer of claim 1, characterized in that the adsorption pump is one or a combination of one or more of a getter pump, an ion pump, a cryopump.

15. The mass spectrometer of claim 14, characterized in that the adsorption pump comprises a first adsorption pump and a second adsorption pump, the first adsorption pump is a getter pump using alloy as getter material, and the second adsorption pump is an ion pump, the getter pump is a primary pump of the mass spectrometer, and the ion pump communicates with the first chamber or the second chamber.

16. The mass spectrometer of claim 14, characterized in that the adsorption pump is an ion pump, the mass spectrometer includes a sector magnetic deflection mass analyzer, and the sector magnetic deflection mass analyzer and the ion pump share the magnet.

17. A method for establishing a vacuum system of a mass spectrometer, the vacuum system comprising a first chamber and a second chamber communicated by mean of a flow restricting structure, an ion trap disposed in the first chamber, and an adsorption pump disposed in the second chamber, and the method comprising the steps of: pre-pumping, by an external vacuum pump, the second chamber until the gas pressure of the second chamber is reduced below activation gas pressure of the adsorption pump; activating the adsorption pump; starting the adsorption pump to reduce the gas pressure of the first chamber to be within the working gas pressure range of the ion trap, and sealing the first chamber and the second chamber, disconnecting the external vacuum pump, and using the adsorption pump as a primary pump of the vacuum system to maintain vacuum level of the first chamber and the second chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 is a schematic view showing the structure of a mass spectrometer according to a first embodiment of the invention.

[0038] FIG. 2 is a schematic view showing the structure of a mass spectrometer according to a second embodiment of the invention.

[0039] FIG. 3 is a schematic view showing the structure of a mass spectrometer according to a third embodiment of the invention.

[0040] FIG. 4 is a schematic view showing the structure of a mass spectrometer according to a fourth embodiment of the invention.

[0041] FIG. 5 is a flow chart showing a method for establishing a vacuum system of a mass spectrometer in the fourth embodiment of the invention.

REFERENCE NUMERALS

[0042] First chamber 1; Second chamber 2; Adsorption pump 3; Flow restricting structure 4; Ion trap 5; Capillary sample introducing means 61; Membrane sample introducing means 62; Vacuum pump interface 7.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. On the basis of the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making inventive labor fall within the scope of protection of the present invention.

Terms

[0044] As used herein, the term “adsorption pump” refers to a trapping pump that operates based on the adsorption principle and forms a vacuum environment by chemical adsorption, low-temperature adsorption, adsorption after ionization, and the like, and includes a getter pump, an ion pump, a cryopump, and the like.

[0045] As used herein, the term “getter pump” refers to a chemisorption pump consisting of a getter with a large surface area. Most commonly used are non-evaporable getters (NEG) sintered from alloy materials such as zirconium vanadium iron alloys. After activation (heating in vacuum), it can absorb various reactive gases such as hydrogen, oxygen, water, carbon monoxide, carbon dioxide and nitrogen through three processes of surface adsorption, surface dissociation and bulk diffusion.

[0046] As used herein, the term “compact mass spectrometer” refers to a mass spectrometer having a size, volume, weight and power consumption that is significantly smaller than conventional laboratory mass spectrometers, small desktop or portable in volume; weight less than 20 kg.

[0047] As used herein, the term “activation gas pressure” refers to a low-enough safe pressure for adsorption pump activation operation, typically in the range of ≤1 Pa.

First Embodiment

[0048] Referring to FIG. 1, this embodiment provides a compact mass spectrometer, the mass spectrometer has a hermetical chamber, the chamber is in communication with the external environment only through a vacuum interface. The vacuum interface is normally not open, only open when sample injection or other special conditions are required. When the vacuum interface is not open, the chamber of the mass spectrometer is substantially completely closed, so that the vacuum level inside the mass spectrometer is substantially maintained as long as the vacuum interface is not open.

[0049] The hermetical chamber interior comprises a first chamber 1 and a second chamber 2, the second chamber 2 being provided with an adsorption pump 3, the first chamber 1 and the second chamber 2 being in communication with each other via a flow restricting structure 4. The adsorption pump 3 is a pump operating based on the adsorption principle, which uses chemical adsorption, low-temperature adsorption, adsorption after ionization, etc. to form a vacuum environment. Since the adsorption amount is limited, it is impossible to continue adsorbing the gas after reaching the adsorption equilibrium, it is not suitable to operate at a high gas pressure, otherwise the service life is greatly decreased. In addition, the adsorption pump 3 typically requires activation before it is first operated. Activation of the adsorption pump 3 requires lowering the second chamber 2 in which the adsorption pump 3 is located below the activation gas pressure (typically in the range of ≤1 Pa) and activating it by heating, energizing, or the like. The adsorption pump 3 can be stably operated after activation. In addition, in order for the adsorption pump 3 to continue to be stably operated, the gas pressure in the second chamber 2 should also be stably maintained at the working gas pressure of the adsorption pump 3, which is typically less than 10.sup.−2 Pa. In this embodiment, the adsorption pump 3 may be one or a combination of one or more of a getter pump, an ion pump, a cryopump.

[0050] Regarding the first chamber 1, the first chamber 1 is typically used for housing functional components, such as ion generation, feeding, control, storage or analysis and the like, of a mass spectrometer, such as an ion source, ion optics, mass analyzer, detector or the like. As one or more of the ion source, the ion optics, the mass analyzer, the detector, etc., it is generally necessary to operate in a suitable gas pressure environment. Optionally by setting the gas pressure range of the first chamber 1 at P1>10.sup.−2 Pa, functional components such as the ion trap 5 and the like can be satisfied to operate in a preferred barometric environment, while the manipulation, storage and mass analysis and the like of ions are performed efficiently, in this embodiment, it is preferable to use the ion trap 5, which is relative smaller in size compared to other ion optics, mass analyzers and the like, so that the size requirements of the components of the miniaturized mass spectrometer are well met.

[0051] It should be noted that the ion source, the ion optics, the mass analyzer, and the detector may be entirely disposed in the first chamber 1, or may be partially disposed in the first chamber 1 and partially disposed in the second chamber 2 or other chambers or the external environment, without departing from the spirit and scope of the present invention. Preferably, a detector, a mass analyzer and/or an ion source are centrally disposed within the first chamber 1, by centralizing the detector, the mass analyzer and/or the ion source in the first chamber 1, i.e. the first chamber 1 acts as the main chamber housing the apparatus, while the second chamber 2 is assisted by the flow-restricting structure 4 to provide a buffer for the vacuumed gas flow, the second chamber 2 can take up less space and keep the gas pressure of the first chamber 1 stable.

[0052] This embodiment uses the adsorption pump 3 to vacuum the first chamber 1 and the second chamber 2, and under the action of the flow restricting structure 4, such that the first chamber 1 and the second chamber 2 can provide different gas pressure environments to form a two-stage differential pumping. Specifically, mounting an adsorption pump 3 in the second chamber 2, and providing a flow restricting structure 4 between the first chamber 1 and the second chamber 2, the adsorption pump 3 may be used as the primary pump to maintain vacuum conditions of the mass spectrometer, and the working gas pressure of the first chamber 1 is adjusted by configuring or adjusting the size of the opening of the flow restricting structure 4 or the flow rate of the sample introducing device (corresponding to the vacuum interface in this embodiment) so that the gas pressure of the first chamber 1 is within an gas pressure range suitable for the operation of its internal components.

[0053] On the other hand, since the first chamber 1 and the second chamber 2 are hermetical with respect to the external environment, as long as the chamber is vacuumed below the activation gas pressure of the adsorption pump 3 before deliver from the factory and the adsorption pump 3 is activated, the activated adsorption pump 3 can satisfy the load requirements for vacuuming the hermetical chamber without the need to provide the vacuum system with a turbo pump or any other type of large-volume pre-pumped pump, facilitating the miniaturization and lightening of the vacuum system.

[0054] In embodiments of the invention, the flow restricting structure 4 includes, but is not limited to, one or more of a flow restricting aperture a flow restricting valve, or a flow restricting tube and the like. The pore size, pipe diameter, etc. of the flow restricting structure 4 may be determined based on a combination of the gas pressure requirements of the first chamber 1, the flow rate of the sample introducing device, and the pumping speed of the adsorption pump 3. The presence of the flow restricting structure 4 not only regulates the gas pressure level of the first chamber 1, but also stabilizes the gas pressure environment within the first chamber 1 by restricting the vacuumed flow so that the functional components within the first chamber 1 operate in a stable gas pressure environment.

[0055] In summary, since the mass spectrometer in this embodiment uses the adsorption pump 3 as a primary pump, which is vacuumed based on the adsorption principle after activation of the adsorption pump 3, the energy consumption thereof is almost negligible, and the size of the adsorption pump 3 is small and is particularly suitable for use as a vacuum system of a portable mass spectrometer without external power supply, making a portable or even a palmtop mass spectrometer possible. Moreover, both the first chamber 1 and the second chamber 2 are all hermetical chambers, and the gas pressure condition in the chambers can be maintained for a long period of time, and the vacuum environment maintained for a long period of time can prevent the adsorption pump 3 from reaching adsorption saturation too quickly, which is advantageous for extending the service life of the adsorption pump 3.

[0056] In other embodiments of the invention, the adsorption pump 3 may be an ion pump, the mass analyzer of the mass spectrometer may be a sector magnetic deflection mass analyzer, and the sector magnetic deflection mass analyzer and the ion pump share a magnet. The manner in which the magnetic sector magnetic deflection mass analyzer and the ion pump share magnets can effectively simplify the apparatus and reduce the volume of the apparatus. In this embodiment, the adsorption pump is an individual ion pump, i.e. the mass spectrometer includes no other type of adsorption pump, in order to effectively simplify the apparatus while meeting the test requirements.

[0057] The ion source can be, for example, electrospray, corona discharge, dielectric barrier discharge, glow discharge, electron impact, photoionization, and the like.

[0058] The mass analyzer may be, for example, an ion trap, quadrupole, time-of-flight, sector magnetic deflection, ion cyclotron resonance, or the like.

[0059] The detector may be, for example, an electron multiplier, a Faraday cartridge, a photomultiplier tube, a microchannel plate, or the like.

[0060] In this embodiment, the first chamber 1 is in communication with the external environment only through a capillary sample introducing means 61 having a valve for opening/closing the sample introducing, and the valve can be closed to maintain a vacuum environment inside the mass spectrometer when the mass spectrometer does not need to perform the sample introducing, avoiding air ingress to reduce the service life of the adsorption pump 3. When an analytical test is required, the valve can be opened and a capillary sample introducing means 61 can be used to perform the sample introducing. In some embodiments, the sample introducing means may further comprise a thermal desorption assembly for converting a solid or liquid sample to a gaseous sample for analysis.

Second Embodiment

[0061] FIG. 2 is a schematic view showing a structure of a mass spectrometer in a second embodiment of the present invention.

[0062] In this embodiment, the main structure of the mass spectrometer comprises a first chamber 1, a second chamber 2, an adsorption pump 3, a flow restricting structure 4, an ion trap 5. Besides that in this embodiment, the adsorption pump 3 further includes two types of adsorption pumps 3 such as a getter pump and an ion pump, other components and reference numerals are the same as those shown in FIG. 1 of the first embodiment, and will not be described in detail here.

[0063] As shown in FIG. 2, in this embodiment, the adsorption pump 3 arranged in the second chamber 2 comprises a first adsorption pump 31, which is a getter pump with an alloy as getter material, and a second adsorption pump 32, which is an ion pump, the adsorption pump is the primary pump of the mass spectrometer, the ion pump can be in communication with the first chamber 1 or with the second chamber 2, in this embodiment the ion pump is in communication with the second chamber 2.

[0064] Getter pump which fully use chemisorption without evaporation and electromagnetic contamination, are typically used in large systems as auxiliary pumps for increasing the pumping speed and increasing the vacuum level, i.e., after pre-pumping with turbo pumps or molecular pumps, the getter pump is used to further vacuum to increase the vacuum level. Whereas in this embodiment, the combination of the adsorption pump 3 using a getter pump and an ion pump acts as a primary pump for the mass spectrometer, and by configuring the chamber as a whole as a hermetical chamber to maintain the hermetical conditions required for the getter pump itself to operate, it is not necessary to configure the vacuum system with a turbo pump, a molecular pump or any other bulky and energy-intensive pre-pumping pump, facilitating the miniaturization and lightening of the vacuum system. Preferably, in this embodiment, the getter pump is a getter pump with alloy as the getter material, which has the advantages of high pumping speed (>10 l/s for air), large amount of getter, light weight (it can be lightened to 16 g), no vibration, no power supply for pumping at room temperature after activation, and can be used repeatedly, and is suitable for establishing vacuum systems of miniaturized mass spectrometers.

[0065] The ion pump can help remove inert gases that are more difficult to adsorb by the getter pump, and also has a certain pumping rate for the air. The combination of the two can effectively adsorb or remove gases of different constituents in the sample gas or air, and in particular, the getter pump has several times of the pumping speed and thousands of times of the adsorption capacity for hydrogen gas, and is well suited for tests using hydrogen gas as a carrier gas such as gas chromatography or tests containing hydrogen gas at a high concentration in the sample gas.

Third Embodiment

[0066] FIG. 3 is a schematic view showing a structure of a mass spectrometer in a third embodiment of the invention.

[0067] In this embodiment, the main structure of the mass spectrometer comprises a first chamber 1, a second chamber 2, an adsorption pump 3, a flow restricting structure 4, an ion trap 5. Besides that in this embodiment, the sample introducing means is a membrane sample introducing means 62 (membrane interface), other components and reference numerals are the same as those shown in FIG. 2 of the second embodiment, and will not be described in detail herein. The use of the membrane sample introducing means 62 effectively compromises the vacuum maintenance and the convenience to introduce the sample in the first and second chambers 1, 2.

Fourth Embodiment

[0068] FIG. 4 is a schematic view showing the structure of a mass spectrometer in a fourth embodiment of the invention.

[0069] In this embodiment, the main structure of the mass spectrometer comprises a first chamber 1, a second chamber 2, an adsorption pump 3, a flow restricting structure 4, an ion trap 5. Besides that in this embodiment the vacuum interface of the chamber of the mass spectrometer in communication with the external environment further comprises a vacuum pump interface 7, other components and reference numerals are the same as shown in FIG. 1 of the first embodiment and will not be described in detail here.

[0070] In this embodiment, the mass spectrometer further comprises a vacuum pump interface 7 in communication with the second chamber 2, via which the second chamber 2 can be in communication with an external vacuum pump (not shown in the figure) for pre-pumping the gas pressure of the second chamber 2 to within the activation gas pressure range of the adsorption pump 3.

[0071] In the above manner, the pre-pumping of the second chamber 2 by the external vacuum pump facilitates the gas pressure inside the second chamber 2 to reach quickly the gas pressure environment required for the activation of the adsorption pump 3, and after the end of the activation, the external vacuum pump can be disconnected to maintain only the electric energy required for the operation of the adsorption pump 3 by the internal power supply to stably maintain the normal operation of the vacuum system of the mass spectrometer in time.

[0072] With reference to FIG. 5, this embodiment further provides a method for establishing a vacuum system for a mass spectrometer. The vacuum system comprises a first chamber 1 and a second chamber 2 communicated by mean of a flow restricting structure 4, with an ion trap 5 disposed in the first chamber 1 and an adsorption pump 3 disposed in the second chamber 2, the method of forming comprises the steps of: [0073] S1: pre-pumping, by an external vacuum pump, the second chamber 2 until the gas pressure of the second chamber 2 is reduced below activation gas pressure of the adsorption pump 3; [0074] S2: activating adsorption pump 3; [0075] S3: starting the adsorption pump 3 to reduce the gas pressure of the first chamber 1 to be within the working gas pressure range of the ion trap 5, and [0076] S4: sealing the first chamber 1 and the second chamber 2, and disconnecting the external vacuum pump, using the adsorption pump 3 as the primary pump of the vacuum system to maintain the vacuum level of the first chamber 1 and the second chamber 2.

[0077] In the above manner, the vacuum system can be provided with a vacuum pump connected at the vacuum pump interface 7 just prior to initial use, for example before delivering from the factory, to complete the pre-vacuuming and activation of the adsorption pump 3, and subsequent vacuum levels can be maintained with the adsorption pump 3. After shipment, the chamber can also be opened for service or maintenance using the vacuum pump interface 7, increasing the convenience of production and maintenance of the mass spectrometer.

[0078] It is to be noted that, although in the above embodiments, the vacuum system of the mass spectrometer comprises only two stages of a first chamber 1 and a second chamber 2, however, the embodiments described above are only illustrative, in other embodiments of the invention, three-stage or more vacuum systems may be used, i.e., additional chambers may be provided between the first chamber 1 and the second chamber 2, and the ion source, ion trap 5 and the like ion generating means, ion optics, detector, or mass analyzer may be positioned as desired.

[0079] In the above-described embodiments of the invention, the adsorption pump 3 may be used as a primary pump. The adsorption pump 3 has advantages of high pumping speed (pumping speed for air>10 l/s, weight of getter material is only 16 g), large adsorption capacity, light weight, room temperature pumping without power supply after activation, and can be used repeatedly, adopting the adsorption pump 3 as a primary pump, reduces the volume of the mass spectrometer, reduces the power consumption and weight of the mass spectrometer, and makes it easier to achieve portability.

[0080] In the above embodiment of the invention, preferably at least one of the adsorption pumps 3 used in the mass spectrometer is a getter pump with an alloy as getter material and the gas pressure of the second chamber 2 is in the range P2<10.sup.−2 Pa. The getter pump of alloy material has the advantages of high pumping speed, large adsorption capacity, light weight, room temperature pumping without power supply after activation, and can be repeatedly activated and used, and is suitable for miniaturization of mass spectrometer. The gas pressure range P2<10.sup.−2 Pa of the second chamber 2 is a gas pressure environment suitable for the working of getter pump with alloys as getter material, advantageously extending the service life of the getter pump.

[0081] The foregoing are merely preferred embodiments of the present invention and is not intended to limit the invention. It is intended to cover various modifications, equivalents, and improvements within the spirit and principles of the present invention.