Analytical device

Abstract

This allows for the measurement of the vacuum level in a vacuum chamber and provides an analytical device that can be miniaturized. [Solution] The analytical device comprises an ionization unit that generates ions by ionizing a sample, a vacuum chamber into which ions are introduced and the inside is kept under vacuum, a detector that detects ions, and a small vacuum gauge 1 that measures the vacuum level of the vacuum chamber. The small vacuum gauge 1 includes a cylindrical CAN package, a substrate housed within the CAN package, and a vacuum level sensor formed on the substrate.

Description

Technical Field

[0001] The present disclosure relates to an analytical apparatus.

Background Art

[0002] In analytical apparatuses such as mass spectrometers and ion analyzers, ions generated by ionizing a sample are separated and detected in a vacuum chamber. The mass spectrometer disclosed in Japanese Patent Application Laid-Open No. 2023-28190 (Patent Document 1) discloses a first vacuum chamber and a second vacuum chamber in which ion convergence is performed, and an analysis chamber for separating and detecting ions. It is described that each vacuum chamber is maintained at an appropriate degree of vacuum by being evacuated by a vacuum pump.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, the degree of vacuum in a vacuum chamber is monitored using a Pirani gauge. A Pirani gauge is a vacuum gauge that measures the degree of vacuum by utilizing the fact that when gas molecules collide with a platinum wire through which an electric current is flowing, the value of the electric current flowing through the platinum wire changes. Therefore, by installing a Pirani gauge in the vacuum chamber or in the vacuum pipe connecting the vacuum chamber and the vacuum pump, the degree of vacuum in the vacuum chamber can be measured.

[0005] However, since a Pirani gauge requires a certain size in terms of its structure, it is conceivable that the Pirani gauges provided in the vacuum chamber and the vacuum pipe may be an obstacle to miniaturizing the analytical apparatus.

[0006] This disclosure was made to solve these problems and aims to provide an analytical device that can measure the vacuum level of a vacuum chamber and can be miniaturized. [Means for solving the problem]

[0007] An analytical apparatus according to one aspect of this disclosure comprises an ionization unit that generates ions by ionizing a sample, a vacuum chamber into which ions are introduced and which is kept under vacuum, a detector for detecting ions, and a miniature vacuum gauge for measuring the vacuum level of the vacuum chamber. The miniature vacuum gauge includes a cylindrical CAN package, a substrate housed within the CAN package, and a vacuum level sensor formed on the substrate. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide an analytical device that can measure the vacuum level of a vacuum chamber and can be miniaturized. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the analytical apparatus according to the embodiment. [Figure 2] This is a view of a small vacuum gauge from an oblique angle above, before it is installed in a vacuum chamber or vacuum piping. [Figure 3] This figure shows an example of how to install a small vacuum gauge. [Figure 4] This figure shows an example of how to install a small vacuum gauge. [Figure 5] This diagram illustrates the sizes of the miniature vacuum gauge and the Pirani gauge. [Figure 6] This figure shows the typical values ​​for a small vacuum gauge. [Figure 7] This figure shows the TYP value and output equation graph of a small vacuum gauge. [Figure 8] This figure shows the parameters of the output equation for a small vacuum meter. [Figure 9] This figure shows the accuracy of a small vacuum gauge before calibration. [Figure 10] This figure shows the accuracy of the small vacuum gauge after calibration.

Embodiments for Carrying out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0011] [Configuration of the Analyzer] FIG. 1 is a schematic configuration diagram of an analyzer 100 according to an embodiment. The analyzer 100 is, for example, a mass spectrometer or an ion analyzer. More specifically, the analyzer 100 is, for example, an analyzer that utilizes the behavior of ions, molecules, etc. in a vacuum, such as LC-MS (Liquid Chromatography Mass Spectrometry), ICP (Inductively coupled plasma) emission analyzer, helium (He) leak detector, etc.

[0012] In one embodiment, the analyzer 100 is a mass spectrometer, and in a more specific example, it is LC-MS.

[0013] The analyzer 100 includes a small vacuum gauge 1, a main body 5, a vacuum pipe 7, and a vacuum pump 9 according to the embodiment. Note that the size ratio of each part in FIG. 1 is different from the actual size ratio.

[0014] The main body 5 is a part that performs analysis in the analyzer 100. The main body 5 includes an ESI probe 58, an ionization chamber 59, a vacuum chamber 50, and a detector 55. The housing of the main body 5 is generally made of metal.

[0015] The ESI probe 58 generates ions by ionizing a sample in the ionization chamber 59. The ESI probe 58 corresponds to an embodiment of an "ionization device". In one embodiment, the ESI probe 58 is an ESI probe with a heating assist gas that is frequently used in a mass spectrometer.

[0016] The vacuum chamber 50 has its interior maintained under vacuum. Ions are introduced into the vacuum chamber 50 from the ionization chamber 59. In the vacuum chamber 50, the detector 55 detects ions.

[0017] The configuration of the main body 5 will be described in more detail below. The ionization chamber 59 is at approximately atmospheric pressure. The vacuum chamber 50 includes a first vacuum chamber 51, a second vacuum chamber 52, a third vacuum chamber 53, and a fourth vacuum chamber (analysis chamber) 54. Each of the first vacuum chamber 51 to the fourth vacuum chamber 54 is evacuated by a vacuum pump 9. The analyzer 100 has a configuration of a multi-stage differential evacuation system in which the degree of vacuum increases in order from the ionization chamber 59 toward the first vacuum chamber 51, the second vacuum chamber 52, the third vacuum chamber 53, and the fourth vacuum chamber 54.

[0018] An ESI probe 58 is provided as an ion source in the ionization chamber 59. The ESI probe 58 atomizes a sample as minute charged droplets into the ionization chamber 59, thereby ionizing various components contained in the sample. The ionization chamber 59 and the first vacuum chamber 51 are connected through a narrow-diameter desolvation tube 57. Ions generated in the ionization chamber 59 are sucked into the desolvation tube 57 riding on a gas flow formed by the differential pressure between both ends of the desolvation tube 57. The desolvation tube 57 is heated to a predetermined temperature (for example, several hundred degrees). When a charged droplet in which the solvent has not been sufficiently vaporized is sucked into the desolvation tube 57, the vaporization of the solvent is promoted when passing through the desolvation tube 57, and ions are generated.

[0019] Ion guides 511, 521, and 531 are positioned in the first vacuum chamber 51, the second vacuum chamber 52, and the third vacuum chamber 53, respectively. A predetermined voltage is applied to each of the multiple electrodes constituting the ion guides 511, 521, and 531 from a power supply unit (not shown), thereby creating an electric field that focuses and transports ions in the space surrounded by the multiple electrodes. Ions from the sample introduced into the first vacuum chamber 51 are focused by the ion guide 511 and sent to the second vacuum chamber 52 through a small hole provided at the top of the skimmer 512. Ions introduced into the second vacuum chamber 52 are focused by the ion guide 521 and sent to the third vacuum chamber 53. Ions introduced into the third vacuum chamber 53 are focused by the ion guide 531 and sent to the fourth vacuum chamber 54.

[0020] In the fourth vacuum chamber 54, a quadrupole mass filter 541 and a detector 55 are arranged along the ion optical axis. A predetermined voltage is applied from a power supply unit (not shown) to the multiple rod electrodes that make up the quadrupole mass filter 541, thereby creating an electric field that selectively allows ions having a specific mass-to-charge ratio m / z (or being within a specific m / z range) to pass through, while diverting other ions. Of the various ions introduced into the fourth vacuum chamber 54, only those having, for example, a specific m / z pass through the quadrupole mass filter 541 and reach the detector 55.

[0021] The detector 55 outputs an ion intensity signal corresponding to the amount of incident ions. This ion intensity signal is input to a data processing circuit (not shown), where data processing is performed. In one embodiment, the data processing circuit is a computer including a memory and a processor such as a CPU (Central Processing Unit). For example, by scanning the voltage applied to the electrodes constituting the quadrupole mass filter 541 within a predetermined range, the m / z of ions that can pass through the quadrupole mass filter 541 changes. As a result, the data processing unit can create a mass spectrum showing the change in ion intensity over a predetermined m / z range.

[0022] The vacuum pump 9 evacuates the vacuum chamber 50. The vacuum pump 9 includes a rotary pump 91 and a turbomolecular pump 92. The rotary pump 91 evacuates the entire vacuum chamber 50 from atmospheric pressure to a predetermined level of vacuum. In one embodiment, the turbomolecular pump 92 is a triple-inlet turbomolecular pump. The turbomolecular pump 92 evacuates each of the second vacuum chambers 52 to the fourth vacuum chambers 54 at a predetermined flow rate to an even higher level of vacuum.

[0023] Vacuum piping 7 connects the vacuum chamber 50 and the vacuum pump 9. The miniature vacuum gauge 1 measures the vacuum level of the vacuum chamber 50. The miniature vacuum gauge 1 is installed in the vacuum chamber 50 and / or the vacuum piping 7. More specifically, the miniature vacuum gauge 1 may be installed in at least one of the first to fourth vacuum chambers 51 to 54, or in at least one of the vacuum piping 7 connecting each of the first to fourth vacuum chambers 51 to 54 to the corresponding inlet of the vacuum pump 9. When the miniature vacuum gauge 1 is installed in the vacuum piping 7, or when it is placed in the vacuum chamber 50, the effects of temperature (described later) and the effects of malfunction during maintenance of the ion guide can be reduced.

[0024] [Configuration of a small vacuum gauge] Figure 2 is a view of the miniature vacuum gauge 1 from an oblique angle above before installation in the vacuum chamber 50 or vacuum piping 7. Figures 3 and 4 show examples of installation of the miniature vacuum gauge 1. Figures 3 and 4 illustrate the case where the miniature vacuum gauge 1 is installed in the vacuum piping 7 (more specifically, on the wall of the vacuum piping 7), but it can also be installed in the vacuum chamber 50 in the same way. In Figures 3 and 4, the extension direction of the vacuum piping 7 is defined as the X direction, the extension direction of the leg portion 109 of the miniature vacuum gauge 1 is defined as the Y direction, and the direction perpendicular to the XY direction is defined as the Z direction. Referring to Figure 3, the side in the negative Y direction relative to the wall of the vacuum piping 7 is the inside of the vacuum piping 7 and is a vacuum environment. The side in the positive Y direction relative to the wall of the vacuum piping 7 is the outside of the vacuum piping 7 and is the atmospheric environment side. Figure 3 is a cross-sectional view of the structure surrounding the miniature vacuum gauge 1 in the XY plane. Figure 4 is a cross-sectional view of the structure surrounding the miniature vacuum gauge 1 in the YZ plane.

[0025] Referring to Figures 2 to 4, the miniature vacuum gauge 1 includes a CAN package 10, a circuit board 12, a sensor 11, and an electronic circuit 13.

[0026] The CAN package 10 is a cylindrical package. The CAN package 10 includes a bottom portion 101 that forms the bottom of the cylinder and a wall portion 102 that surrounds the bottom portion 101. The CAN package 10 also includes legs 109 provided on the side of the bottom portion 101 where the substrate 12 is not installed. After the CAN package 10 is installed in the vacuum chamber 50 or vacuum piping 7, any unnecessary portions of the legs 109 may be cut off.

[0027] The circuit board 12 is housed within the CAN package 10. Sensor 11 is a sensor for measuring vacuum level, mounted on the substrate 12, and corresponds to one embodiment of a "vacuum level sensor". In one embodiment, sensor 11 is a sensor that measures vacuum level using a thermocouple. Sensors that measure vacuum level using a thermocouple are more durable and reliable than those that use platinum wires, which are prone to breakage, like Pirani gauges. Also, since there is no need to replace the platinum wires, maintenance is not required. The small vacuum gauge 1 is, for example, the TPM227 from Kodenshi.

[0028] In one embodiment, the substrate 12 is installed on the bottom 101 of the CAN package 10. With this configuration, the sensor 11 is protected from the surroundings by the wall portion 102.

[0029] In one embodiment, a sensor 11 and an electronic circuit 13 are formed on a substrate 12 using MEMS (Micro Electro Mechanical Systems) technology. The sensor 11 is connected to the electronic circuit 13. The electronic circuit 13 is connected to a leg portion 109 provided on the opposite side via a bottom portion 101. The output value (voltage value) of the sensor 11 is output to the outside via the electronic circuit 13 and the leg portion 109. By using MEMS technology, it is possible to miniaturize the small vacuum gauge 1.

[0030] The size of the miniature vacuum gauge 1 is relatively small, specifically less than 10 mm in size. For example, if the height of the wall portion 102 of the miniature vacuum gauge 1 (h in Figure 3, hereinafter also referred to as the "length of the miniature vacuum gauge") is 10 mm or less, it is equal to or less than the radial height of other components (for example, components that connect pipes) arranged around the outer circumference of the vacuum chamber 50 or vacuum piping 7, making it easy to miniaturize the analytical device 100.

[0031] Furthermore, as another example, if the diameter of the small vacuum gauge 1 is 10 mm or less, the area it occupies on the outer surface of the vacuum chamber 50 or vacuum piping 7 is small, so there is no need to make the outer surface of the vacuum chamber 50 or vacuum piping 7 large, and the analysis device 100 can be easily miniaturized. For example, in the example in Figures 3 and 4, a hole 6 into which the wall portion 102 of the small vacuum gauge 1 and the O-ring 31 are fitted is formed in the wall surface of the vacuum piping 7, but if a larger vacuum gauge is installed in the hole 6, problems arise such as the O-ring 31 not fitting, or the vacuum gauge itself not fitting into the hole 6 at all.

[0032] In one embodiment, the size of the small vacuum gauge 1 is IC size (approximately 5 mm in diameter x 3 mm in height).

[0033] In one embodiment, the miniature vacuum gauge 1 is installed in the vacuum piping 7 via an O-ring 31. Since the wall portion 102 of the CAN package 10 is cylindrical, it can be stably held in place when fitted inside the O-ring. Therefore, the wall portion 102 of the CAN package 10 can be stably installed in the circular opening via the O-ring. In the example shown in Figure 3, the wall portion 102 of the miniature vacuum gauge 1 is fitted into a hole 6 formed in the vacuum piping 7, and the O-ring 31 is installed to fill the gap between the hole 6 and the wall portion 102. This seals the space between the hole 6 and the wall portion 102. Similarly, when the miniature vacuum gauge 1 is installed in the vacuum chamber 50 via the O-ring 31, the O-ring 31 is installed to seal the space between the hole formed in the vacuum chamber 50 and the wall portion 102.

[0034] The inventors verified through actual experiments that there are no problems with airtightness and pressure measurement even when a small vacuum gauge 1 is installed on the wall (curved surface) of a cylindrical vacuum pipe 7. Specifically, the inventors calculated the appropriate O-ring diameter and compression allowance for the diameter and diameter tolerance of the hole 6 in the vacuum pipe 7, and performed airtightness and pressure measurements using the selected O-ring, proving that there were no problems with the measured values.

[0035] The miniature vacuum gauge 1 is positioned with the sensor 11 facing the vacuum environment and the legs 109 facing the atmospheric environment. In the example shown in Figures 3 and 4, the legs 109 are connected to the electronic circuit of the substrate 34 on the atmospheric environment side. As a result, the output value (voltage value) of the sensor 11 is input to a data processing circuit (e.g., a computer) via the electronic circuit 13, the legs 109, and the electronic circuit of the substrate 34, and converted into a measured value in the data processing device. This measured value is pressure (atmospheric pressure). The substrate 34 is, for example, an FR4 (Flame Retardant Type 4) substrate. The substrate 34 is fixed to the vacuum chamber 50 or vacuum piping 7 by screws 33. In the example shown in Figures 3 and 4, a spacer 32 is provided between the substrate 34 and the vacuum piping 7 to facilitate the stable placement of the flat substrate 34 on the curved surface of the vacuum piping 7. In other examples, instead of providing a spacer 32, a flat section may be provided in the vacuum piping 7, and the sensor 11 may be installed on this flat section.

[0036] Furthermore, as an ingenious design by the inventors for installing the miniature vacuum gauge 1, the miniature vacuum gauge 1 is held in place by a spacer 32 (or a substrate 34 if there is no spacer 32) to prevent it from moving to the outside of the vacuum pipe 7. For this reason, a retaining portion 71 is formed on the inner wall surface of the vacuum pipe 7 to prevent the miniature vacuum gauge 1 from moving inside the vacuum pipe 7, but there is no need to form a retaining portion on the outer wall surface. This makes it easier to process the vacuum pipe 7 than when a retaining portion is also formed on the outer wall surface. In addition, the miniature vacuum gauge 1 can be installed in vacuum pipes 7 with thinner walls than when a retaining portion is formed on the outer wall surface.

[0037] [Comparison with Pirani Gauge in the Comparative Example] Figure 5 is a diagram illustrating the sizes of the small vacuum gauge 1 according to the embodiment and the Pirani gauge according to the comparative example. In this specification, when simply referred to as "Pirani gauge," it refers to a Pirani gauge of a structure and size that has been conventionally used for pressure measurement, as exemplified in the following comparative example. Although the structures of the Pirani gauges of a structure and size that have been conventionally used for pressure measurement and the micro-Pirani vacuum gauge described later differ from each other, both are vacuum gauges that measure the degree of vacuum by utilizing the fact that the value of the current flowing through the Pirani wiring changes when gas molecules collide with the Pirani wiring while an electric current is flowing through it, and are therefore collectively referred to as "Pirani vacuum gauges."

[0038] The size ratio of the miniature vacuum gauge 1 and the Pirani gauge in Figure 5 differs from the actual size ratio. In one embodiment, the size of the miniature vacuum gauge 1 is 4.65 mm in diameter and 2.7 mm in length. On the other hand, the size of the Pirani gauge in the comparative example is 18 mm in diameter and 56 mm in length. The Pirani gauge in the comparative example is more than 3.9 times larger in diameter and more than 20.7 times larger in length than the miniature vacuum gauge 1 in this embodiment. In other words, the miniature vacuum gauge 1 in this embodiment is more than 74% smaller in diameter and more than 95% smaller in length than the Pirani gauge in the comparative example. Furthermore, a Pirani gauge usually requires a casing to house the platinum wire and hermetic seal in order to protect the platinum wire. The size of the Pirani gauge including the casing is larger than the size of the Pirani gauge itself, which is approximately 2 cm in diameter and 6 cm in length.

[0039] When installing a Pirani gauge in an analytical instrument, a relatively expensive hermetic seal is required to ensure electrical connection between the platinum wire (Pirani wiring) and the outside environment (atmospheric environment) while maintaining airtightness at the installation site. Furthermore, spot welding is required to connect the hermetic seal to the Pirani gauge, which contributes to the increased cost of the Pirani gauge.

[0040] Furthermore, if the Pirani gauge includes a casing, airtight welding is required to connect the casing to the analytical instrument, which also contributes to increased costs when using Pirani gauges.

[0041] Furthermore, when installing the Pirani gauge in the main body of the analyzer, the casing's opening must be positioned parallel to the ion beam to prevent ion or gas flows from colliding with the platinum wire. Also, to maintain the measurement accuracy of the Pirani gauge, it must be installed away from areas of the main body that become hot. Additionally, because the platinum wire is very thin (for example, about 25 μm in diameter) and easily broken by mechanical shock, it must be installed in a recessed location where it will not be accidentally touched during maintenance of the main body.

[0042] Furthermore, in mass spectrometers, the vacuum level of the first vacuum chamber is generally measured, but a gas flow containing ions is generated in the first vacuum chamber due to the differential pressure between the ends of the desolvation tube. Therefore, the Pirani gauge needs to be positioned and oriented so that the gas flow from the first vacuum chamber does not collide with the platinum wire.

[0043] Furthermore, since the desolvation tube is heated to several hundred degrees Celsius, this heat is transferred to the first vacuum chamber through the housing (generally made of metal). Some of this heat is also transferred to the first vacuum chamber by the gas flow. Additionally, since the set temperature of the desolvation tube and the set temperature of the ESI probe with heating assist gas are both user-configurable parameters, the way heat is transferred to the first vacuum chamber varies depending on the settings. Therefore, the Pirani gauge needs to be placed in a location unaffected by temperature changes.

[0044] Furthermore, since the ion guide in the first vacuum chamber is a component that the user maintains themselves, the Pirani gauge needs to be installed in a way that prevents accidental contact during maintenance of the ion guide in the first vacuum chamber.

[0045] As described above, Pirani gauges are relatively large, and their installation locations are limited, which hinders the miniaturization of the analytical instrument itself. Related to this, the housing of the instrument needs to be formed in a complex shape, which increases costs.

[0046] Furthermore, when a Pirani gauge is installed in the vacuum piping connecting the main unit and the vacuum pump, the Pirani gauge is relatively long relative to the radial direction of the vacuum piping (approximately 6 cm including the hermetic seal), which creates dead volume and hinders the miniaturization of the device.

[0047] For example, in a mass spectrometer, if you try to place another unit (such as a power supply unit) next to the vacuum piping, a gap the length of a Pirani gauge will remain between the vacuum piping and the power supply unit.

[0048] As described above, conventional analytical instruments, including those using Pirani gauges, suffer from high costs and difficulty in miniaturization due to the size and structural characteristics of Pirani gauges.

[0049] On the other hand, according to the analytical apparatus 100 including the compact vacuum gauge 1 of this embodiment, cost reduction and miniaturization are possible.

[0050] First, the small vacuum gauge 1 itself is only a fraction of the size of a Pirani gauge, so it doesn't take up much space. Related to this, its small size allows for a wide range of installation options when attaching it to the analytical device 100. Furthermore, the shape of the hole 6 to be drilled in the installation area can be small and simple.

[0051] Furthermore, in the compact vacuum gauge 1, since the sensor 11 is housed in the CAN package 10, when it is installed in the vacuum chamber 50, there is no need to take precautions to prevent ion flow and gas flow from interfering with the sensor's measurement values, nor is there any need to take precautions to prevent accidentally shocking the sensor 11 during maintenance. Therefore, there is no need to process the housing into a complex shape, and the range of possible installation locations is further expanded.

[0052] Furthermore, when the small vacuum gauge 1 is installed in the vacuum piping 7, the dead volume around the installation area is reduced, allowing for greater flexibility in the layout of other units within the analyzer, which in turn facilitates miniaturization of the analyzer 100.

[0053] Furthermore, since the miniature vacuum gauge 1 is held in place by an inexpensive O-ring 31 and substrate 34, a casing and hermetic seal for holding the vacuum gauge are unnecessary, unlike those required for Pirani gauges. As a result, when using the miniature vacuum gauge 1, the installation area can be kept airtight at a low cost without using expensive spot welding and airtight welding.

[0054] While the small vacuum gauge 1 can also be installed in the vacuum chamber 50 or vacuum piping 7 by other methods such as soldering, brazing, welding, or bonding, it is preferable to install it using an O-ring from the standpoint of reducing costs and labor.

[0055] As described above, the analytical device 100 can measure the vacuum level of a vacuum chamber and provides an analytical device that can be miniaturized.

[0056] Therefore, the mass spectrometer including the compact vacuum gauge 1 according to this embodiment can be manufactured more compactly and inexpensively than the mass spectrometer using a general Pirani gauge, as described in the comparative example. Relatedly, the vacuum chamber 50 can be made smaller, which shortens the vacuuming time and improves user convenience. As a result, it becomes easier for users who previously had difficulty using mass spectrometers to obtain them, thus expanding the possibilities for performing mass analysis in new fields.

[0057] However, conventionally, Pirani gauges have been used exclusively for measuring vacuum levels in analytical instruments such as mass spectrometers, and therefore, no conversion formula (output equation) for converting the output value of the small vacuum gauge 1 into pressure was prepared in the analytical instrument. Accordingly, in order to obtain a measurement value that is closer to the true vacuum level in the analytical instrument, the inventors created an output equation as shown in the following example.

[0058] [Correction for output and individual differences in small vacuum gauges] In this embodiment, the TPM227 from Kodenshi Corporation was used as the small vacuum gauge 1.

[0059] In order to obtain a measurement closer to the true vacuum level when using the miniature vacuum gauge 1, and to reduce individual differences in vacuum level measurements, the inventors derived the output equation as follows and performed individual calibration of the miniature vacuum gauge 1.

[0060] In this specification, the conversion formula for converting the output value of a vacuum gauge to pressure (atmospheric pressure) is also referred to as the "output equation." Note that both the output value of the Pirani gauge and the output value of the miniature vacuum gauge 1 are voltage values.

[0061] While the output equation for a conventional Pirani gauge can be expressed in a single equation, the output equation for the small vacuum gauge 1 is difficult to express in a single equation. Therefore, the inventors divided the required pressure range into multiple pressure intervals and derived the output equation. To derive the output equation, they used assumed equations (with undetermined parameter values) and known measured values ​​for each pressure interval, and optimized the parameter values ​​using the least squares method. Using this output equation, it is possible to obtain measured values ​​that are close to the true vacuum level.

[0062] Specifically, the inventors obtained a table of typical values ​​(TYP values) for a small vacuum gauge from the manufacturer (Figure 6). They then represented the relationship between the output value and pressure in Figure 6 as the "Manufacturer's Nominal TYP Value" graph in Figure 7. Next, based on the trend in the graph in Figure 7, the inventors divided the required pressure range into four pressure intervals, P0 to P3. Finally, they performed least-squares approximation for each pressure interval to create the output equation. Figure 8 is a table showing the parameter values ​​of the output equation for each pressure interval.

[0063] Next, the inventors verified whether the measurements from multiple small vacuum gauges 1, obtained using the output equation, matched the actual pressure (atmospheric pressure) measured using a Pirani gauge. In other words, the inventors verified whether the measurements from the small vacuum gauges 1 and the measurements from the Pirani gauge matched within the pressure range for which measurement was required.

[0064] As a result, it was found that for the pressure range requiring measurement, the measurements from multiple miniature vacuum gauges 1 matched those from the Pirani gauge. However, the inventors found that in some pressure ranges (low pressure ranges), the required accuracy could not be met due to variations in the output values ​​of individual miniature vacuum gauges 1. Therefore, measurements were taken at a single point (one pressure) in the low pressure range using both the Pirani gauge and the miniature vacuum gauge 1. By multiplying the output equation by the deviation rate of the miniature vacuum gauge measurement relative to the Pirani gauge measurement as a correction coefficient, it was experimentally verified that the required accuracy could be met even in the low pressure range. This correction method reduces individual differences in vacuum values, allowing pressure to be measured with the required accuracy even in constant pressure ranges.

[0065] Specifically, the inventors compared the measured values ​​of the miniature vacuum gauge 1 from four different lots (Lot A to Lot B) with the measured values ​​of a Pirani gauge (Figure 9). In Figure 9, in most pressure ranges, the measured values ​​of all miniature vacuum gauges 1 fell within the target accuracy range (inside the two target accuracy lines). However, as indicated by the circles, in the low pressure range of 10 Pa or less, the measured values ​​of some miniature vacuum gauges fell outside the target accuracy range. In the example in Figure 9, the target accuracy range is ±30% of the measured value of the Pirani gauge in the pressure range of 1 to 300 Pa. Therefore, in the low pressure range of 10 Pa or less, calibration was performed by multiplying the output equation by the deviation rate from the TYP value pressure as a correction coefficient. As a result of this calibration, the measured values ​​of the miniature vacuum gauge 1 fell within the target accuracy range, as shown in Figure 10.

[0066] According to the method for deriving the output equation described above, the vacuum level in the medium vacuum region of mass spectrometers, ion analyzers, etc., can be measured with accurate values. Furthermore, by using the above measurement correction method in conjunction with this method, individual differences in the small vacuum gauge 1 can be reduced, and a more accurate vacuum level can be measured.

[0067] [Other forms] A micro-pirani sensor may be used as the sensor for the miniature vacuum gauge 1. A micro-pirani sensor is a sensor that measures vacuum using tiny pirani wiring fabricated on a substrate using MEMS technology. For example, tiny titanium wire can be used as the tiny pirani wiring. In other words, the miniature vacuum gauge 1 is a miniature pirani vacuum gauge made using MEMS technology. More specifically, the miniature vacuum gauge 1 may be a micro-pirani vacuum gauge in which a micro-pirani sensor is housed in a CAN package using MEMS technology. Similar to miniature vacuum gauges that measure vacuum using thermocouples, micro-pirani vacuum gauges have advantages over pirani gauges, such as the ability to miniaturize the main body of the analytical instrument and a lower possibility of accidental contact during maintenance.

[0068] For the miniature vacuum gauge 1, other small packages (for example, the packages used in POSIFA's PVC3000 series) may be used instead of the CAN package 10.

[0069] While a custom-made package can be used for the small vacuum gauge 1, using a commercially available CAN package 10 saves time and expense in creating the package.

[0070] While a rectangular package may also be used, a cylindrical package is superior because it is easier to drill holes for installation and easier to seal with an O-ring. However, when using a small vacuum gauge with a short length (h in Figure 3), it is also possible to attach the small vacuum gauge with a surface seal.

[0071] Furthermore, in the miniature vacuum gauge 1, instead of a package, a small sensor may be mounted on a small plate-shaped member using MEMS technology.

[0072] Similarly, the miniature vacuum gauge 1 may be one in which the micropirani sensor is located in a small package other than a CAN package, or on a small plate-shaped member. For example, the POSIFA PVC3000 series or the POSIFA PVC4101 may be used.

[0073] [Aspect] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following embodiments.

[0074] (Section 1) An analytical apparatus according to one embodiment comprises an ionization unit that generates ions by ionizing a sample, a vacuum chamber into which ions are introduced and the inside is kept under vacuum, a detector for detecting ions, and a small vacuum gauge for measuring the vacuum level of the vacuum chamber. The small vacuum gauge includes a cylindrical CAN package, a substrate housed within the CAN package, and a vacuum level sensor formed on the substrate.

[0075] According to the analytical apparatus described in paragraph 1, it is possible to measure the vacuum level of a vacuum chamber and to provide an analytical apparatus that can be miniaturized.

[0076] (Section 2) In the analytical apparatus described in paragraph 1, the size of the small vacuum gauge is 10 mm or less.

[0077] According to the analytical apparatus described in paragraph 2, it is a fraction of the size of a Pirani gauge, and does not take up much space. Related to this, because it is small, it can be installed in a wide range of locations when attached to an analytical apparatus. Furthermore, the shape of the hole to be drilled in the installation part can be small and simple.

[0078] (Section 3) In the analytical apparatus described in paragraph 1 or 2, the miniature vacuum gauge measures the degree of vacuum using a thermocouple.

[0079] (Section 4) In the analytical apparatus described in any one of paragraphs 1 to 3, the miniature vacuum gauge is a miniature Pirani vacuum gauge manufactured using MEMS technology.

[0080] (Section 5) In the analytical apparatus described in any one of paragraphs 1 to 4, the small vacuum gauge is installed in the vacuum chamber via an O-ring.

[0081] According to the analytical apparatus described in Section 5, an O-ring can be used to seal the gap between the hole formed in the vacuum chamber and the small vacuum gauge.

[0082] (Section 6) The analytical apparatus described in any one of paragraphs 1 to 5 further comprises a vacuum pump for evacuating the vacuum chamber and vacuum piping connecting the vacuum chamber and the vacuum pump. A small vacuum gauge is installed in the vacuum piping via an O-ring.

[0083] According to the analytical apparatus described in Section 6, an O-ring can be used to seal the gap between the hole formed in the vacuum tubing and the small vacuum gauge.

[0084] (Section 7) The analytical apparatus described in any one of paragraphs 1 to 6 is a mass spectrometer.

[0085] The mass spectrometer described in Section 7 can be manufactured to be smaller and less expensive than a typical mass spectrometer using a Pirani gauge.

[0086] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0087] 1 Miniature vacuum gauge, 5 Main body, 6 Hole, 7 Vacuum piping, 9 Vacuum pump, 10 CAN package, 11 Sensor, 12, 34 Circuit board, 13 Electronic circuit, 31 O-ring, 32 Spacer, 33 Screw, 50 Vacuum chamber, 51 First vacuum chamber, 52 Second vacuum chamber, 53 Third vacuum chamber, 54 Fourth vacuum chamber, 55 Detector, 57 Desolvation tube, 58 ESI probe, 59 Ionization chamber, 91 Rotary pump, 92 Turbomolecular pump, 100 Analytical instrument, 101 Bottom, 102 Wall, 109 Legs, 511, 521, 531 Ion guide, 512 Skimmer, 541 Quadrupole mass filter.

Claims

1. An ionization unit that generates ions by ionizing the sample, The aforementioned ions are introduced into a vacuum chamber, and the inside is kept under vacuum. A detector for detecting the aforementioned ions, The vacuum chamber is equipped with a small vacuum meter for measuring the degree of vacuum, The aforementioned small vacuum gauge is A cylindrical CAN package, A substrate housed within the aforementioned CAN package, An analytical apparatus including a vacuum sensor formed on the substrate.

2. The analytical apparatus according to claim 1, wherein the size of the small vacuum gauge is 10 mm or less.

3. The analytical apparatus according to claim 1 or 2, wherein the miniature vacuum gauge measures the degree of vacuum using a thermocouple.

4. The analytical apparatus according to claim 1 or 2, wherein the miniature vacuum gauge is a miniature Pirani vacuum gauge fabricated using MEMS technology.

5. The analytical apparatus according to claim 1 or 2, wherein the small vacuum gauge is installed in the vacuum chamber via an O-ring.

6. The aforementioned analytical device is A vacuum pump for evacuating the aforementioned vacuum chamber, The system further comprises vacuum piping connecting the vacuum chamber and the vacuum pump, The analytical apparatus according to claim 1 or 2, wherein the small vacuum gauge is installed in the vacuum piping via an O-ring.

7. The analytical apparatus according to claim 1 or 2, wherein the analytical apparatus is a mass spectrometer.

Images