Photomultiplier quenching device and single particle aerosol time-of-flight mass spectrometer

Abstract

The application discloses a photoelectric multiplier extinction device and a single-particle aerosol time-of-flight mass spectrometer, and the photoelectric multiplier extinction device comprises a mirror barrel, a diaphragm mounting barrel and a diaphragm; the mirror barrel is in a hollow barrel structure with both ends being open, and the two ends of the mirror barrel are connected to an ellipsoidal mirror and a photoelectric multiplier respectively; the diaphragm mounting barrel comprises a mounting portion and an extinction portion, the mounting portion is sealingly connected to a port of the mirror barrel, a light passing hole is formed in the center of the mounting portion, and the diaphragm is sealingly mounted in the light passing hole; the extinction portion is located in the mirror barrel and extends in the direction of the extension of the mirror barrel towards the ellipsoidal mirror, a light extinction hole is formed in the center of the extinction portion, and the inner wall surface of the mirror barrel, the hole wall surface of the light extinction hole and the end surface of the extinction portion close to the mirror all comprise light absorption material surfaces. The application can reduce the incident amount of the clutter interference signal in the detection area of the photoelectric multiplier, make the photoelectric multiplier work stably and improve the accuracy of the detection result.

Description

Technical Field

[0001] This application relates to the field of mass spectrometry technology, and in particular to a photomultiplier extinction device and a single-particle aerosol time-of-flight mass spectrometer. Background Technology

[0002] Aerosols are relatively stable mixtures of gas and particulate matter, formed by the uniform dispersion of liquid or solid particles in a gas. The aerodynamic particle size is typically 0.002-100 μm. To obtain comprehensive information about aerosols, it is necessary to detect the chemical composition of both the gas and the particulate matter. Common techniques for detecting gaseous components include gas chromatography-flame particle detection, gas chromatography-mass spectrometry (GC-MS), proton transfer reaction mass spectrometry (PTMS), photoionization mass spectrometry (PISA), and chemical ionization mass spectrometry (CISA). For the detection of particulate matter chemical composition, techniques can be divided into two main categories: offline and online. Offline techniques often use membrane filters to collect particulate matter and combine them with ion chromatography, atomic absorption spectrometry, gas chromatography-mass spectrometry (GC-MS), and neutron-excited X-ray emission spectroscopy for analysis. Online techniques can employ aerosol mass spectrometry and single-particle aerosol time-of-flight mass spectrometry (TOF-MS).

[0003] Currently, detecting the chemical composition of gases and particulate matter in aerosols often requires two or more instruments to obtain results, and differences in different instruments and detection technologies can affect the results. Therefore, using a single set of detection instruments for online, real-time detection of the chemical composition of gases and particulate matter in aerosols is particularly necessary and offers better economic benefits.

[0004] In existing technologies, single-particle aerosol time-of-flight mass spectrometry (TOF-MS) is a high-temporal-resolution instrument for monitoring and analyzing the composition of single-particle aerosols in the atmosphere. It features the ability to simultaneously detect the particle size, multiple chemical components, and mixing states of individual fine particles in the atmosphere. A single-particle aerosol TOF-MS consists of an aerodynamic lens sample introduction system, a laser diameter measurement system, a laser ionization system, and a mass spectrometry detection system to acquire mass spectrum signals and confirm the composition of single-particle aerosols.

[0005] Aerosol particles in the atmosphere enter the vacuum system inside the instrument under atmospheric pressure. Under the action of an aerodynamic lens, the particles are focused into a collimated particle beam. Upon leaving the aerodynamic lens, the beam undergoes supersonic gas expansion and enters the diameter measurement zone. In the diameter measurement zone, there are two laser beams with a fixed spacing. The particle passes through both laser beams sequentially, and the transit time between the two beams is obtained. This time is used to calculate both the aerodynamic diameter of the particle and the time it takes for the particle to reach the center of the ionization zone. When the particle reaches the center of the ionization zone, the ionization laser is activated, and the particle is ionized. The positive and negative ions generated by ionization are detected separately by a bipolar time-of-flight mass analyzer, obtaining the mass spectrum of each positive and negative ion. This allows for the analysis of components such as metals, sulfates, nitrates, ammonium salts, organic carbon, and elemental carbon within the particle.

[0006] Ellipsoidal mirrors and photomultipliers are positioned corresponding to the locations of the two laser beams. The transit time of the particle between the two laser beams is obtained through the two photomultipliers. For details, refer to... Figure 1a As shown, an ellipsoidal reflector 200 and a photomultiplier 300 are arranged opposite each other, connected by a lens barrel 110a. A lens mounting bracket 120a is located on the side of the lens barrel 110a closest to the photomultiplier 300. A plano-concave lens 130a is mounted at the center of the lens mounting bracket 120a via a lens clamping plate 140a. During operation, particles generate scattered light signals after colliding with the laser. These scattered light signals are reflected by the ellipsoidal reflector at their respective positions and, under the further converging effect of the plano-concave lens, enter the detection area of ​​the corresponding photomultiplier. The signals received sequentially by the detection areas of the two photomultipliers are amplified and shaped before being input into a timing circuit. The timing circuit records the transit time of the particle between the two laser beams.

[0007] However, in actual laser diameter measurement, the signal received by the photomultiplier's detection zone includes not only scattered light signals (i.e., the useful signal) but also clutter interference signals. When the clutter interference signal is strong, it will interfere with the photomultiplier's detection zone's reception of the scattered light signal, making the photomultiplier unable to work stably, and in severe cases, even making it impossible to obtain detection results.

[0008] Theoretical analysis suggests that due to the non-ideal state of the incident laser beam or insufficient processing precision of the ellipsoidal reflector, the collision between particles and the laser simultaneously generates scattered light signals and laser clutter signals. Both signals are reflected by the ellipsoidal reflector and converged into the detection area of ​​the photomultiplier. Furthermore, the photomultiplier possesses extremely high sensitivity and ultra-fast response time, capable of converting even weak light signals into electrical signals, resulting in a large amount of unwanted laser clutter interference signals.

[0009] In related technologies, attempts have been made to adjust the incident laser beam to make it axially incident with a clean periphery, and to improve the curvature and coating processes of the ellipsoidal reflector to make it closer to the ideal state. However, the actual test results are still unsatisfactory. Summary of the Invention

[0010] To address at least one of the problems mentioned in the background art, embodiments of this application provide a photomultiplier extinction device and a single-particle aerosol time-of-flight mass spectrometer. The photomultiplier extinction device is installed between an ellipsoidal reflector and a photomultiplier, which can reduce the amount of clutter interference signals incident in the detection area of ​​the photomultiplier, enabling the photomultiplier to work stably and improving the accuracy of the detection results.

[0011] To achieve the above objectives, the first aspect of this application provides a photomultiplier extinction device for connecting an ellipsoidal reflector and a photomultiplier in a single-particle aerosol time-of-flight mass spectrometer, wherein the ellipsoidal reflector and the detection area of ​​the photomultiplier are arranged opposite to each other.

[0012] The photomultiplier extinction device includes a reflector tube, an neutral density filter mounting tube, and a neutral density filter;

[0013] The mirror tube extends along the line connecting the ellipsoidal mirror and the detection area. The mirror tube has a hollow cylindrical structure with openings at both ends. One end of the mirror tube is connected to the ellipsoidal mirror, and the other end of the mirror tube is connected to the photomultiplier.

[0014] The neutral density filter mounting cylinder includes a mounting part and an extinction part. The mounting part is sealed and connected to the port of the mirror cylinder near the detection area. A through-hole is provided in the center of the mounting part.

[0015] The light-reducing filter is sealed and installed inside the light-passing hole on the side near the detection area;

[0016] The extinction part is connected to the mounting part and is located inside the mirror tube. The extinction part extends along the extension direction of the mirror tube towards the ellipsoidal mirror, and the extension length of the extinction part is 1 / 2 to 2 / 3 of the length of the mirror tube. An extinction hole is provided at the center of the extinction part, and the extinction hole is interconnected with the light-passing hole. The diameter of the extinction hole is 1 / 3 to 1 / 2 of the inner diameter of the mirror tube.

[0017] The inner wall surface of the mirror tube, the wall surface of the extinction hole, and the end face of the extinction part near the mirror all include light-absorbing material surfaces.

[0018] In one feasible implementation, the aperture wall surface includes a light-absorbing material surface.

[0019] In one feasible implementation, the extinction hole includes a first extinction hole and a second extinction hole that are interconnected.

[0020] The first extinction hole is located at the end of the extinction part away from the ellipsoidal reflector, and the first extinction hole is a through hole; the second extinction hole is located at the end of the extinction part close to the ellipsoidal reflector, and the second extinction hole is a tapered hole that flares out toward the end close to the ellipsoidal reflector.

[0021] In one feasible implementation, an annular mounting groove is formed on the wall surface of the light-passing hole, and a neutral density filter sealing ring is provided in the mounting groove, with the neutral density filter embedded in the neutral density filter sealing ring.

[0022] In one feasible implementation, the circumferential surface of the neutral density filter mounting cylinder located inside the mirror barrel is in close contact with the inner wall surface of the mirror barrel, and an annular first sealing groove is formed on one of the circumferential surface of the neutral density part and the inner wall surface of the mirror barrel, and a first sealing ring is provided in the first sealing groove.

[0023] A second annular sealing groove is provided on the outer wall surface of the reflector tube, and a second sealing ring is provided in the second sealing groove.

[0024] In one feasible implementation, a mirror barrel flange is provided at the port of the mirror barrel near the detection area, and the mounting part is provided with a mounting flange extending out of the mirror barrel, and the mirror barrel flange and the mounting flange are bolted together.

[0025] In one feasible implementation, the ellipsoidal reflector is provided with a reflector flange at one end near the reflector tube, the reflector flange is provided with a reflector convex stop, the reflector convex stop is fitted into the tube hole at the corresponding end of the reflector tube, and the reflector flange is connected to the reflector tube by bolts.

[0026] In one feasible implementation, a reflective matting sheet is also included. The photomultiplier is provided with a light-transmitting sheet, which is located on the side of the photomultiplier near the mounting portion. Along the line connecting the ellipsoidal reflector and the detection area, the orthographic projection of the light-transmitting sheet at least covers the detection area.

[0027] A stop groove is provided at the center of the end face of the mounting part near the detection area. The stop groove is connected to the light-passing hole. The reflective extinction sheet is installed in the stop groove. A through reflective extinction hole is provided at the center of the reflective extinction sheet. The hole wall surface of the reflective extinction hole includes a light-absorbing material surface.

[0028] In one feasible implementation, the reflective extinction aperture includes a first reflective extinction aperture and a second reflective extinction aperture that are interconnected.

[0029] The first reflective extinction hole is located at the end of the reflective extinction sheet away from the detection area, and the first reflective extinction hole is a through hole; the second reflective extinction hole is located at the end of the reflective extinction sheet close to the detection area, and the second reflective extinction hole is a tapered hole that flares out towards the detection area.

[0030] A second aspect of this application provides a single-particle aerosol time-of-flight mass spectrometer, including an ellipsoidal reflector, a photomultiplier, and a photomultiplier extinction device as described above. The ellipsoidal reflector is disposed opposite to the detection area of ​​the photomultiplier, and the photomultiplier extinction device is connected between the ellipsoidal reflector and the photomultiplier.

[0031] In one feasible implementation, the photomultiplier includes a housing and a photomultiplier body. The photomultiplier body has the detection area. The photomultiplier body is installed in the housing. The housing has a detection port corresponding to the detection area. The housing is sealed to the mounting part of the photomultiplier extinction device.

[0032] This application provides a photomultiplier extinction device and a single-particle aerosol time-of-flight mass spectrometer. The photomultiplier extinction device is connected between an ellipsoidal mirror and a photomultiplier, and includes a mirror tube, a neutral density filter mounting tube, and a neutral density filter.

[0033] The two ends of the reflector tube are connected to a photomultiplier and an ellipsoidal reflector, respectively. The hollow structure in the middle can provide a transmission space for the laser signal generated after the laser collides with the particles.

[0034] The extinction section of the neutral density filter mounting tube is located inside the mirror tube. The extinction section extends along the mirror tube towards the ellipsoidal mirror, and both the inner wall of the mirror tube and the end face of the extinction section facing the ellipsoidal mirror include light-absorbing material surfaces. An extinction hole is formed at the center of the extinction section, and the hole wall includes a light-absorbing material surface. The inner wall of the mirror tube absorbs clutter interference signals generated by the laser beam, the ellipsoidal mirror, or other issues before entering the extinction section. The end face of the extinction section near the mirror tube absorbs some scattered light signals and a large amount of clutter interference signals reflected near the edge of the ellipsoidal mirror, actively distributing the scattered light signals and clutter interference signals before they enter the extinction hole, trapping a large amount of clutter interference signals and some scattered light signals outside the extinction hole. The hole wall also absorbs clutter interference signals generated by the laser beam, the ellipsoidal mirror, or other issues. Therefore, the arrangement of each light-absorbing material surface reduces clutter interference signals incident on the detection area of ​​the photomultiplier.

[0035] Meanwhile, the extension length of the extinction section and the aperture setting of the extinction hole can provide transmission space for the scattered light signal to enter the detection area of ​​the photomultiplier. This ensures that while reducing the incident amount of clutter interference signals, there is still a sufficient amount of scattered light signal to converge into the detection area of ​​the photomultiplier, so that the detection area of ​​the photomultiplier can detect the scattered light signal, thereby enabling the single-particle aerosol time-of-flight mass spectrometer to obtain detection results.

[0036] The mounting section is located at the port on the side of the reflector barrel near the detection area of ​​the photomultiplier. The mounting section is sealed to the reflector barrel, and the neutral density filter is sealed to the mounting section. The two sealed connections work together to prevent ambient air from entering the reflector barrel, thus avoiding leakage caused by the internal vacuum environment during operation and ensuring stable operation of the diameter measurement system.

[0037] The light-reducing filter is installed inside the light-passing hole and positioned close to the detection area of ​​the photomultiplier. This allows for light reduction and filtering of the light signal entering the detection area of ​​the photomultiplier, which helps to further reduce noise interference signals entering the detection area of ​​the photomultiplier.

[0038] In summary, by setting up a photomultiplier extinction device between the ellipsoidal reflector and the photomultiplier, the amount of clutter interference signal incident in the detection area of ​​the photomultiplier can be reduced, and the scattered light signal with sufficient incident amount can be converged to the detection area of ​​the photomultiplier, enabling the photomultiplier to work stably and improving the accuracy of the detection results.

[0039] The single-particle aerosol time-of-flight mass spectrometer includes an ellipsoidal mirror, a photomultiplier, and the aforementioned photomultiplier extinction device. The photomultiplier extinction device is connected between the ellipsoidal mirror and the photomultiplier and has the same beneficial effect. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1a This is a schematic diagram of the connection structure of a photomultiplier, a lens barrel, and an ellipsoidal reflector provided in the prior art.

[0042] Figure 1 A schematic diagram of the connection structure of the photomultiplier, the photomultiplier extinction device and the ellipsoidal reflector provided in the embodiments of this application;

[0043] Figure 2 This is a schematic diagram of the structure of the photomultiplier extinction device provided in the embodiments of this application;

[0044] Figure 3 This is a front view of the neutral density filter mounting cylinder provided in an embodiment of this application;

[0045] Figure 4 for Figure 3 AA view;

[0046] Figure 5 This is a diagram of the photomultiplier detection signal received by a photomultiplier in the prior art.

[0047] Figure 6 This is a diagram of the photomultiplier detection signal received by the photomultiplier in an embodiment of this application.

[0048] Explanation of reference numerals in the attached figures:

[0049] 110a - Lens barrel; 120a - Lens mounting bracket; 130a - Plano-concave lens; 140a - Lens clamping plate;

[0050] 100-Photomultiplier extinction device;

[0051] 110 - Mirror barrel; 111 - Mirror barrel flange; 112 - Second sealing groove;

[0052] 120 - Neutral density filter mounting cylinder; 121 - Mounting part; 1211 - Mounting flange; 1212 - Light transmission hole;

[0053] 1213 - Mounting groove; 1214 - Stop groove; 122 - Matte finish section; 1221 - First matte finish hole; 1222 - Second matte finish hole; 1223 - First sealing groove;

[0054] 130-ND filter;

[0055] 140 - Reflective matting plate; 141 - First reflective matting aperture; 142 - Second reflective matting aperture;

[0056] 151-First sealing ring; 152-Second sealing ring; 153-Neutral neutral density filter sealing ring; 154-Photoelectric sensor

[0057] Multiplier seal ring;

[0058] 200-ellipsoidal reflecting mirror;

[0059] 300 - Photomultiplier; 301 - Photomultiplier body; 3011 - Transmitter sheet;

[0060] 310 - Box body;

[0061] 320 - Transparent lid. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. It is worth noting that the embodiments described in the accompanying drawings are only some embodiments of this application, and not all embodiments. That is, the embodiments described with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0063] The following will combine Figures 1-6 An extinction device 100 for a photomultiplier provided in an embodiment of this application will be described.

[0064] This application provides a photomultiplier extinction device 100, referring to... Figures 1-4 As shown, the photomultiplier extinction device 100 is connected between the ellipsoidal reflector 200 and the photomultiplier 300 of the single-particle aerosol time-of-flight mass spectrometer, with the ellipsoidal reflector 200 and the detection area of ​​the photomultiplier 300 being arranged opposite to each other.

[0065] The photomultiplier extinction device 100 includes a mirror tube 110, an neutral density filter mounting tube 120, and a neutral density filter 130.

[0066] The mirror tube 110 extends along the line connecting the ellipsoidal mirror 200 and the detection area. The mirror tube 110 has a hollow cylindrical structure with openings at both ends. One end of the mirror tube 110 is connected to the ellipsoidal mirror 200, and the other end of the mirror tube 110 is connected to the photomultiplier 300.

[0067] The neutral density filter mounting tube 120 includes a mounting part 121 and a light-absorbing part 122. The mounting part 121 is sealed and connected to the port of the mirror tube 110 near the detection area. A through light-passing hole 1212 is opened in the center of the mounting part 121.

[0068] The neutral density filter 130 is sealed and installed inside the light-passing aperture 1212 on the side near the detection area.

[0069] The extinction section 122 is connected to the mounting section 121 and is located inside the mirror tube 110. The extinction section 122 extends along the extension direction of the mirror tube 110 towards the ellipsoidal mirror 200, and the extension length of the extinction section 122 is 1 / 2 to 2 / 3 of the length of the mirror tube 110. An extinction hole is provided at the center of the extinction section 122, and the extinction hole communicates with the light-passing hole 1212. The diameter of the extinction hole is 1 / 3 to 1 / 2 of the inner diameter of the mirror tube 110.

[0070] The inner wall surface of the mirror tube 110, the wall surface of the extinction hole, and the end face of the extinction part 122 near the ellipsoidal mirror 200 all include light-absorbing material surfaces.

[0071] The ellipsoidal reflector 200 has a near-end focusing point and a far-end focusing point. The near-end focusing point serves as the collision point between the particle and the laser, while the far-end focusing point corresponds to the detection area of ​​the photomultiplier 300. In this way, the laser signal generated by the collision between the laser and the particle can be focused to the far-end focusing point by the reflection of the ellipsoidal reflector 200 and received by the detection area.

[0072] The two ends of the reflector barrel 110 are connected to the photomultiplier 300 and the ellipsoidal reflector 200, respectively. The hollow structure in the middle provides a transmission space for the laser signal generated after the laser collides with the particles. In one embodiment, the reflector barrel 110 can be a circular cylindrical structure, and the central axis of the reflector barrel 110 coincides with the line connecting the two focal points of the ellipsoidal reflector 200, which facilitates the alignment of the detection area, the neutral density filter 130, and the ellipsoidal reflector 200.

[0073] Each wall surface and end face includes a light-absorbing material surface. In specific embodiments, the light-absorbing material can be coated with a light-absorbing material as in the prior art to form a light-absorbing material surface, or the reflector barrel 110 and the light-absorbing part 122 can be integrally formed from the light-absorbing material to form a light-absorbing material surface. The light-absorbing material surface does not transmit light that shines on it, nor does it produce reflection, a large number of glare spots, or reflections, thereby achieving a light-absorbing and light-absorbing effect.

[0074] The extinction section 122 of the neutral density filter mounting cylinder 120 is located inside the mirror cylinder 110. The extinction section 122 extends along the mirror cylinder 110 towards the ellipsoidal mirror 200, and both the inner wall surface of the mirror cylinder 110 and the end face of the extinction section 122 facing the ellipsoidal mirror 200 include light-absorbing material surfaces. An extinction hole is formed at the center of the extinction section 122, and the hole wall surface includes a light-absorbing material surface. The inner wall surface of the mirror cylinder 110 can absorb clutter interference signals generated by the laser beam, the ellipsoidal mirror 200, or other issues before entering the extinction section 122. (Refer to...) Figure 2 It is known that the scattered light signal reflected from the edge of the ellipsoidal mirror 200 is mainly distributed around the outer periphery of the extinction aperture. The end face of the extinction section 122 near the mirror barrel 110 can absorb part of the scattered light signal and a large amount of clutter interference signal reflected from the edge of the ellipsoidal mirror 200, so that the scattered light signal and clutter interference signal are actively distributed before entering the extinction aperture, and a large amount of clutter interference signal and part of the scattered light signal are trapped outside the extinction aperture. The aperture wall surface of the extinction aperture can also absorb clutter interference signals caused by the laser beam, the ellipsoidal mirror 200 or other problems. Therefore, the arrangement of each light-absorbing material surface reduces the clutter interference signal incident on the detection area of ​​the photomultiplier 300.

[0075] The extension length of the extinction section 122 is greater than or equal to half the extension length of the mirror tube 110. This avoids the situation where a large amount of scattered light signals and clutter interference signals would concentrate at the extinction aperture and enter the detection area of ​​the photomultiplier 300 due to an excessively small extension length, causing the photomultiplier 300 to malfunction. Conversely, if the extension length of the extinction section 122 is less than or equal to two-thirds the extension length of the mirror tube 110, this avoids the situation where an excessively large extension length would cause the scattered light signals and clutter interference signals to be completely extinct, reducing the amount of scattered light signals incident in the detection area and preventing the acquisition of detection results.

[0076] The diameter of the extinction aperture is greater than or equal to one-third of the inner diameter of the mirror tube 110. This avoids the risk that a small aperture diameter, while extincting clutter interference signals, would also significantly reduce scattered light signals, potentially failing to meet the incident light limit in the detection area. Conversely, if the diameter is too large, a large amount of clutter interference signals would enter the extinction aperture, increasing the extinction pressure on the aperture and consequently allowing a large amount of clutter interference signals to enter the detection area and affect the detection results.

[0077] The extension length of the extinction section 122 and the aperture setting of the extinction hole provide transmission space for the scattered light signal to enter the detection area of ​​the photomultiplier 300. This ensures that while reducing the incident amount of clutter interference signals, there is still a sufficient amount of scattered light signal to converge into the detection area of ​​the photomultiplier 300, so that the detection area of ​​the photomultiplier 300 can detect the scattered light signal, thereby enabling the single-particle aerosol time-of-flight mass spectrometer to obtain detection results.

[0078] The mounting part 121 is located at the port of the reflector barrel 110 near the detection area of ​​the photomultiplier 300. The mounting part 121 is sealed to the reflector barrel 110, and the neutral density filter 130 is sealed to the mounting part 121. The two sealed connections work together to prevent ambient air from entering the interior of the reflector barrel 110, thus avoiding vacuum leakage during operation and ensuring stable operation of the diameter measurement system.

[0079] The neutral density filter 130 is installed inside the light-passing aperture 1212 and positioned close to the detection area of ​​the photomultiplier 300. This allows it to filter and reduce the light signal entering the detection area of ​​the photomultiplier 300, further reducing noise interference signals. In one embodiment, the diameter of the central hole on the mounting portion 121 can be slightly larger than the diameter of the hole at the end of the extinction aperture furthest from the ellipsoidal reflector 200. This ensures that all light signals transmitted through the extinction aperture can pass through the neutral density filter 130, thus enabling the neutral density filter 130 to reduce the light intensity of all incident light signals.

[0080] In summary, by setting a photomultiplier extinction device 100 between the ellipsoidal reflector 200 and the photomultiplier 300, the amount of clutter interference signal incident in the detection area of ​​the photomultiplier 300 can be reduced, and the scattered light signal with sufficient incident amount can be concentrated in the detection area of ​​the photomultiplier 300, enabling the photomultiplier 300 to work stably and improving the accuracy of the detection results.

[0081] Reference Figure 5 The following is a description of the use of... Figure 1a The image shows the photomultiplier detection signal obtained from sample gas testing using a single-particle aerosol time-of-flight mass spectrometer with the existing technology structure shown. Figure 6 The following is an example of using this application. Figure 1 The photomultiplier detection signal was obtained by detecting the same sample gas using a single-particle aerosol time-of-flight mass spectrometer with the structure shown. All other conditions (such as the incident laser beam adjustment device and the fabrication process of the ellipsoidal mirror) were identical for both methods.

[0082] Among them, Figure 5 and Figure 6In the diagram, the horizontal axis represents time, and the vertical axis represents signal strength, displaying the voltage value. The intermittent spike pulse signal is the useful signal C2 formed by the scattered light signal to be measured, while the signal between adjacent pulse signals is the noise floor signal C1 (clutter interference signal). Figure 5 The noise floor signal is Figure 6 The noise floor is 5 to 6 times lower. By comparison, it can be seen that by adding a laser extinction device to the photomultiplier, the purpose of reducing the amount of clutter interference signal incident in the detection area of ​​the photomultiplier can be achieved.

[0083] In one feasible implementation, refer to Figure 4 As shown, the wall surface of the light-passing aperture 1212 includes a light-absorbing material surface.

[0084] In this way, when the light signal enters the light-passing aperture 1212, the aperture wall of the light-passing aperture 1212 can also absorb and filter out some of the noise interference signal, enhance the extinction effect of the noise interference signal, and improve the accuracy of the detection results.

[0085] In one feasible implementation, refer to Figure 1 , Figure 2 and Figure 4 As shown, the matting aperture includes a first matting aperture 1221 and a second matting aperture 1222 that are interconnected.

[0086] The first extinction hole 1221 is located at the end of the extinction section 122 away from the ellipsoidal reflector 200, and the first extinction hole 1221 is a cylindrical through hole of equal diameter. The second extinction hole 1222 is located at the end of the extinction section 122 close to the ellipsoidal reflector 200, and the second extinction hole 1222 is a conical hole that flares out toward the end close to the ellipsoidal reflector 200.

[0087] The ratio of the extension lengths of the first extinction hole 1221 and the second extinction hole 1222 can be 2:1 to 3:2. Thus, the second extinction hole 1222 forms a conical surface with a certain extension length. This conical surface is located on the transmission path of some scattered light signals and clutter interference signals. Compared to the extinction section 122, the conical surface is closer to the straight end face of the ellipsoidal reflector 200, forming a larger effective area of ​​light-absorbing material. This allows the conical surface hole to assist the extinction section 122 in approaching the end face of the ellipsoidal reflector 200, effectively extincting some scattered light signals and clutter interference signals. Furthermore, the tapered setting of the conical surface does not cause a significant reduction in the incident amount of scattered light signals and will not affect the detection results.

[0088] In one feasible implementation, refer to Figure 2 and Figure 4As shown, an annular mounting groove 1213 is provided on the wall surface of the light-passing hole 1212. An anti-light filter sealing ring 153 is installed in the mounting groove 1213, and an anti-light filter 130 is embedded in the anti-light filter sealing ring 153.

[0089] In this way, by embedding the neutral density filter 130 into the light passage hole 1212 through the sealing groove, the neutral density filter 130 is fixed, and the external ambient air on the side of the photomultiplier 300 is sealed and isolated from the inside of the mirror barrel 110.

[0090] The diameter measurement system of the single-particle aerosol time-of-flight mass spectrometer includes a diameter measurement cavity body with mounting holes. A reflector tube 110 is fitted into the mounting holes, an ellipsoidal reflector 200 is located inside the diameter measurement cavity body, and a photomultiplier 300 is located outside the diameter measurement cavity body. During operation, the inside of the diameter measurement cavity body is a vacuum system. The neutral density filter 130 prevents ambient air from entering the reflector tube 110, avoiding any impact on the vacuum state inside the diameter measurement cavity body due to poor sealing of the neutral density filter 130, thus preventing interference with the operation of the diameter measurement system.

[0091] In one feasible implementation, refer to Figure 1 and Figure 2 As shown, the circumferential surface of the light-reducing plate mounting cylinder 120 located inside the mirror barrel 110 is in close contact with the inner wall surface of the mirror barrel 110, and an annular first sealing groove 1223 is formed on one of the circumferential surface of the light-reducing part 122 and the inner wall surface of the mirror barrel 110, and a first sealing ring 151 is provided in the first sealing groove 1223.

[0092] A second annular sealing groove 112 is provided on the outer wall surface of the mirror tube 110, and a second sealing ring 152 is provided in the second sealing groove 112.

[0093] In this way, a sealed connection can be formed between the reflector barrel 110 and the neutral density filter mounting barrel 120, and between the reflector barrel 110 and the mounting hole of the diameter measuring cavity body, thereby preventing external ambient air from entering the interior of the reflector barrel 110 and the diameter measuring cavity body, and preventing it from affecting the operation of the diameter measuring system.

[0094] In one feasible implementation, refer to Figure 1 Combination Figure 3 As shown, a mirror tube flange 111 is provided at the port of the mirror tube 110 near the detection area, and a mounting flange 1211 is provided on the mounting part 121 extending out of the mirror tube 110. The mirror tube flange 111 and the mounting flange 1211 are bolted together.

[0095] A sealing gasket can be installed between the reflector barrel 110 and the mounting part 121 to achieve positioning and sealing connection, improve the sealing between the reflector barrel 110 and the neutral density filter mounting barrel 120, prevent external ambient air from entering the reflector barrel 110 and prevent it from affecting the operation of the diameter measuring system.

[0096] In one feasible implementation, refer to Figure 1 As shown, an ellipsoidal reflector 200 is provided with a reflector flange at one end near the reflector barrel 110. The reflector flange is provided with a reflector convex stop, which is fitted into the barrel hole at the corresponding end of the reflector barrel 110. The reflector flange and the reflector barrel 110 are connected by bolts.

[0097] This ensures that the ellipsoidal reflector 200 and the reflector tube 110 are coaxially aligned, facilitating the alignment of the ellipsoidal reflector 200 and the neutral density filter 130, and achieving a better light extinction effect.

[0098] In one feasible implementation, refer to Figure 1 As shown, the single-particle aerosol time-of-flight mass spectrometer also includes a reflective extinction plate 140 and a photomultiplier 300 with a light-transmitting plate 3011. The light-transmitting plate 3011 is located on the side of the photomultiplier 300 near the mounting part 121. Along the line connecting the ellipsoidal reflector 200 and the detection area, the orthographic projection of the light-transmitting plate 3011 at least covers the detection area.

[0099] The light-transmitting sheet 3011 allows laser light to pass through. In some embodiments, the light-transmitting sheet 3011 may be a glass sheet.

[0100] A stop groove 1214 is provided at the center of the end face of the mounting part 121 near the detection area. The stop groove 1214 is connected to the light-passing hole 1212. The reflective extinction plate 140 is installed in the stop groove 1214. A through reflective extinction hole is provided at the center of the reflective extinction plate 140. The hole wall surface of the reflective extinction hole includes the light-absorbing material surface.

[0101] In this way, considering that the light-transmitting sheet 3011 may have a certain reflectivity to laser, a reflective extinction sheet 140 is provided on the side of the light-transmitting sheet 3011 near the mounting part 121, and the hole wall surface of the reflective extinction hole is formed with a light-absorbing material surface, which can extinct the reflected light and prevent these reflected lights from forming noise interference signals.

[0102] In one feasible implementation, refer to Figure 1 As shown, the reflective extinction aperture includes a first reflective extinction aperture 141 and a second reflective extinction aperture 142 that are interconnected.

[0103] The first reflective extinction hole 141 is located at the end of the reflective extinction plate 140 away from the detection area, and the first reflective extinction hole 141 is a cylindrical through hole of equal diameter. The second reflective extinction hole 142 is located at the end of the reflective extinction plate 140 close to the detection area, and the second reflective extinction hole 142 is a tapered hole that flares out towards the detection area.

[0104] In this way, the first reflective extinction aperture 141 allows a sufficient amount of scattered light signal to be incident on the detection area, and has a certain extinction effect on clutter interference signals caused by the laser beam, the ellipsoidal mirror 200, or other issues. The second reflective extinction aperture 142 faces the light-transmitting plate 3011. Compared with the straight end face of the reflective extinction plate 140 near the light-transmitting plate 3011, it forms a larger annular conical surface, which can increase the effective working area of ​​the light-absorbing material surface and improve the extinction effect on reflected light.

[0105] The following will combine Figure 1 The single-particle aerosol time-of-flight mass spectrometer provided in the embodiments of this application will be described.

[0106] This application provides a single-particle aerosol time-of-flight mass spectrometer, including an ellipsoidal reflector 200, a photomultiplier 300, and a photomultiplier extinction device 100 as described above. The ellipsoidal reflector 200 and the detection area of ​​the photomultiplier 300 are arranged opposite to each other, and the photomultiplier extinction device 100 is connected between the ellipsoidal reflector 200 and the photomultiplier 300.

[0107] The single-particle aerosol time-of-flight mass spectrometer provided in this application includes a photomultiplier extinction device 100 with the structure described above, and has the same beneficial effects, which will not be repeated here.

[0108] In one feasible implementation, refer to Figure 1 As shown, the photomultiplier 300 includes a housing 310 and a photomultiplier body 301. The photomultiplier body 301 has a detection area. The photomultiplier body 301 is installed inside the housing 310. The housing 310 has a detection port corresponding to the detection area. The housing 310 is sealed to the mounting part 121 of the photomultiplier extinction device 100.

[0109] A through cover 320 is provided between the housing 310 and the mounting part 121. The through cover 320 has a through hole at its center allowing laser light to pass through. A through cover protrusion is provided on the side of the through cover 320 closest to the mounting part 121, and this protrusion is fitted into the stop groove 1214 of the light-passing hole 1212. A housing 310 protrusion is provided on the side of the housing 310 closest to the through cover 320, and this protrusion is fitted into the through hole of the through cover 320.

[0110] In this way, the photomultiplier 300 and the mounting part 121 are positioned and installed by the cooperation of the opening and the convex stop, so that the detection area is set opposite to the ellipsoidal reflector 200.

[0111] The aforementioned light-transmitting sheet 3011 can be mounted on the photomultiplier body 301 and corresponds to the detection area. A sealing groove is provided inside the housing 310 around the detection port, and a photomultiplier sealing ring 154 is installed in the sealing groove. The design of the light-transmitting sheet 3011 and the sealing groove can prevent external ambient light from interfering with the detection area.

[0112] It should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" in the description of this application should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0113] The terms “upper,” “lower,” “front,” “back,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0114] The term "multiple" means two or more, unless otherwise precisely specified. The terms "first," "second," "third," "fourth," etc., (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can include implementations in sequences other than those illustrated or described herein.

[0115] The terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A photomultiplier extinction device, characterized in that, For connecting the ellipsoidal reflector and the photomultiplier in a single-particle aerosol time-of-flight mass spectrometer, wherein the ellipsoidal reflector and the detection area of ​​the photomultiplier are arranged opposite to each other; The photomultiplier extinction device includes a reflector tube, an neutral density filter mounting tube, and a neutral density filter; The mirror tube extends along the line connecting the ellipsoidal mirror and the detection area. The mirror tube has a hollow cylindrical structure with openings at both ends. One end of the mirror tube is connected to the ellipsoidal mirror, and the other end of the mirror tube is connected to the photomultiplier. The neutral density filter mounting cylinder includes a mounting part and an extinction part. The mounting part is sealed and connected to the port of the mirror cylinder near the detection area. A through-hole is provided in the center of the mounting part. The light-reducing filter is sealed and installed inside the light-passing hole on the side near the detection area; The extinction part is connected to the mounting part and is located inside the mirror tube. The extinction part extends along the extension direction of the mirror tube towards the ellipsoidal mirror, and the extension length of the extinction part is 1 / 2 to 2 / 3 of the length of the mirror tube. An extinction hole is provided at the center of the extinction part, and the extinction hole is interconnected with the light-passing hole. The diameter of the extinction hole is 1 / 3 to 1 / 2 of the inner diameter of the mirror tube. The inner wall surface of the mirror tube, the wall surface of the extinction hole, and the end face of the extinction part near the mirror all include light-absorbing material surfaces.

2. The photomultiplier extinction device according to claim 1, characterized in that, The wall surface of the light-passing aperture includes a light-absorbing material surface.

3. The photomultiplier extinction device according to claim 1, characterized in that, The extinction hole includes a first extinction hole and a second extinction hole that are interconnected. The first extinction hole is located at the end of the extinction part away from the ellipsoidal reflector, and the first extinction hole is a through hole; the second extinction hole is located at the end of the extinction part close to the ellipsoidal reflector, and the second extinction hole is a tapered hole that flares out toward the end close to the ellipsoidal reflector.

4. A photomultiplier extinction device according to any one of claims 1-3, characterized in that, An annular mounting groove is formed on the wall surface of the light-passing hole, and a light-reducing sheet sealing ring is provided in the mounting groove. The light-reducing sheet is embedded in the light-reducing sheet sealing ring.

5. A photomultiplier extinction device according to any one of claims 1-3, characterized in that, The circumferential surface of the neutral density filter mounting cylinder located inside the mirror barrel is in close contact with the inner wall surface of the mirror barrel, and an annular first sealing groove is formed on one of the circumferential surface of the neutral density part and the inner wall surface of the mirror barrel, and a first sealing ring is provided in the first sealing groove. A second annular sealing groove is provided on the outer wall surface of the reflector tube, and a second sealing ring is provided in the second sealing groove.

6. A photomultiplier extinction device according to any one of claims 1-3, characterized in that, A mirror tube flange is provided at the port of the mirror tube near the detection area, and the mounting part is provided with a mounting flange extending out of the mirror tube. The mirror tube flange and the mounting flange are bolted together. The ellipsoidal reflector has a reflector flange at one end near the reflector tube. The reflector flange has a reflector cam stop, which is fitted into the tube hole at the corresponding end of the reflector tube. The reflector flange and the reflector tube are connected by bolts.

7. The photomultiplier extinction device according to any one of claims 1-3, characterized in that, It also includes a reflective matting sheet, and the photomultiplier is provided with a light-transmitting sheet. The light-transmitting sheet is located on the side of the photomultiplier near the mounting part. Along the line connecting the ellipsoidal reflector and the detection area, the orthographic projection of the light-transmitting sheet at least covers the detection area. A stop groove is provided at the center of the end face of the mounting part near the detection area. The stop groove is connected to the light-passing hole. The reflective extinction sheet is installed in the stop groove. A through reflective extinction hole is provided at the center of the reflective extinction sheet. The hole wall surface of the reflective extinction hole includes a light-absorbing material surface.

8. The photomultiplier extinction device according to claim 7, characterized in that, The reflective extinction aperture includes a first reflective extinction aperture and a second reflective extinction aperture that are interconnected. The first reflective extinction hole is located at the end of the reflective extinction sheet away from the detection area, and the first reflective extinction hole is a through hole; the second reflective extinction hole is located at the end of the reflective extinction sheet close to the detection area, and the second reflective extinction hole is a tapered hole that flares out towards the detection area.

9. A single-particle aerosol time-of-flight mass spectrometer, characterized in that, The device includes an ellipsoidal reflector, a photomultiplier, and a photomultiplier extinction device as described in any one of claims 1-8, wherein the ellipsoidal reflector is disposed opposite to the detection area of ​​the photomultiplier, and the photomultiplier extinction device is connected between the ellipsoidal reflector and the photomultiplier.

10. The single-particle aerosol time-of-flight mass spectrometer according to claim 9, characterized in that, The photomultiplier includes a housing and a photomultiplier body. The photomultiplier body has the detection area. The photomultiplier body is installed in the housing. The housing has a detection port corresponding to the detection area. The housing is sealed to the mounting part of the photomultiplier extinction device.

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