Device and method for measuring photocathode of photomultiplier

Abstract

The invention relates to the technical field of photoelectric detection, and discloses a measuring device and method for a photocathode of a photomultiplier, and the device comprises a light source assembly which serves as a starting condition of equipment driving and is used for emitting measuring light; the collimator is arranged on one side of the light source assembly and used for collimating light emitted by the light source assembly; the optical fiber is arranged at the rear end of the collimator and is used for transmitting the light emitted by the collimator; the camera obscura is arranged on one side of the collimator and is used for shielding stray light of ambient light and a low-frequency magnetic field; and the sensing head is arranged in the camera obscura and is connected with the right port, far away from the collimator, of the optical fiber. By adopting the technical scheme of synchronously measuring the sensitivity of the film layer and the cathode of the photoelectric cathode, compared with a mode of independently testing the thickness of the film layer and the sensitivity of the cathode in the prior art, the problems of low measurement efficiency and poor relevance of test data are effectively solved, and the integrity and the accuracy of performance evaluation of the photoelectric cathode are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection, and particularly to a measuring device and method for a photocathode of a photomultiplier tube. Background Art

[0002] A photomultiplier tube is a photodetector device that can convert a weak optical signal into an electrical signal and amplify it multiplicatively, and is widely used in fields such as spectral analysis, biological detection, and high-energy physics. Its structure generally includes an incident window, a photocathode, an electron multiplication component, an anode, and a tube shell, etc. Among them, the photocathode, as a key component for realizing photoelectric conversion in the photomultiplier tube, its performance has a decisive effect on parameters such as the overall sensitivity, response speed, and signal-to-noise ratio of the photomultiplier tube. In order to evaluate the performance of the photocathode, various testing means are often used in the prior art, including reflectivity testing, elemental composition testing, and cathode sensitivity testing. Among them, reflectivity testing is mainly used to measure the thickness of the photocathode film layer; elemental composition testing is used to analyze the elemental stoichiometry of the photocathode material; and cathode sensitivity testing is used to evaluate the response ability and photoelectric conversion efficiency of the photocathode to incident light.

[0003] However, the existing testing methods each have certain limitations. The accuracy of reflectivity testing is limited, and it is difficult to be used alone for the fine control of the film layer structure; elemental composition testing usually requires the disassembly of the photomultiplier tube, and the photocathode is prone to degradation when exposed to the air environment, which is not conducive to the accuracy and repeatability of the test results, nor is it suitable for the rapid detection of a large number of samples; although cathode sensitivity testing can reflect the photoelectric conversion performance, it lacks structural information on the film layer thickness and material composition.

[0004] In addition, there is still a lack of a dedicated measuring device and method in the prior art that can integrate various testing means into one, while taking into account both the testing efficiency and non-destructiveness. There are also no relevant technical solutions for a comprehensive measuring system for the photocathode of a photomultiplier tube in the published literature. Therefore, there is an urgent need to provide a measuring device and method for the photocathode of a photomultiplier tube with a reasonable structure, accurate measurement, simple operation, and suitable for batch detection to meet the actual needs of optoelectronic device manufacturing and quality control. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a measuring device and method for a photocathode of a photomultiplier tube, which solves the problems that the existing testing device for the photocathode of a photomultiplier tube cannot accurately evaluate the sensitivity distribution of the photocathode, and lacks a high-efficiency and low-cost detection means for the photocathode film layer.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: A measuring device for a photocathode of a photomultiplier tube, comprising:

[0007] A light source assembly, which is used as an enabling condition for device driving and emits measurement light;

[0008] A collimator, which is arranged on one side of the light source assembly and collimates the light emitted by the light source assembly;

[0009] An optical fiber, which is arranged at the rear end of the collimator and transmits the light emitted by the collimator;

[0010] A dark box, which is arranged on one side of the collimator and shields ambient light stray light and low-frequency magnetic fields;

[0011] A sensing head, which is arranged inside the dark box and is connected to the right port of the optical fiber far from the collimator, and is used to output the interference light generated by the light in the optical fiber and the input reflected light, and transmit it back through the optical fiber;

[0012] A fixing component, which is arranged inside the dark box and is used to fix the photomultiplier tube to be tested and enable it to move in a two-dimensional plane;

[0013] A low-voltage source, which is connected to the input end of the photomultiplier tube to be tested and is used to transmit the light reflected by the photomultiplier tube to be tested to the optical fiber;

[0014] A microammeter, whose input end is connected to the cathode output end of the photomultiplier tube to be tested through a wire;

[0015] A beam splitter, which is connected to the bottom port of the optical fiber and is used to split the interference light in the optical fiber to obtain a spectrogram;

[0016] A computer and acquisition software, whose input ends are respectively connected to the beam splitter and the microammeter, and are connected to the low-voltage source through the output end, and are used to process and analyze the information of the photomultiplier tube to be tested obtained.

[0017] Preferably, the light source assembly includes a light source and a drive circuit. The rear end of the drive circuit is connected to the collimator, and the light source and the drive circuit are electrically connected.

[0018] Preferably, the fixing component includes a moving platform and a fixture. The moving platform is arranged inside the dark box. The moving platform and the fixture are connected by bolts, and the fixture and the sensing head are vertically distributed.

[0019] Preferably, the light source includes a white light diode, a green light diode and a blue light diode, and the central wavelength of the light source is 390nm - 420nm.

[0020] Preferably, the collimator internally includes two groups of vacuum diaphragms, both of which are 5um - 100um.

[0021] Preferably, the distance between the collimator and the photomultiplier tube to be tested is 10mm - 50mm.

[0022] Preferably, the dark box is filled with permalloy and the interior is painted black entirely.

[0023] Preferably, the voltage range of the low-voltage source is 0V - 500V.

[0024] Preferably, the sensitivity of the microammeter is 10 -12 -10 -15 A.

[0025] A method for measuring a photomultiplier photoelectric cathode, comprising the following steps:

[0026] S1. Fix the photomultiplier to be measured on a moving platform with a fixture and close the dark box;

[0027] S2. Set the collimator parameters in the computer and acquisition software, and at the same time set the step size, moving range, interval time of the moving platform and the loading voltage of the low-voltage source. Then start the drive circuit to drive the light source to emit light with a power of milliwatts. After being collimated by the collimator, the light enters the optical fiber;

[0028] S3. The light entering the optical fiber is converged by the sensing head, irradiates the photoelectric cathode surface of the photomultiplier to generate a photocurrent, which is collected by the microammeter. At the same time, the sensing head also receives the light reflected from the photomultiplier to be measured, transmits it into the optical fiber to generate interference, and the interference light is split by the beam splitter to obtain an optical intensity spectrogram;

[0029] S4. According to the computer and acquisition software set in step S2, the current value is collected from the microammeter and the optical intensity spectrogram is collected from the beam splitter at this time, and then they are processed and analyzed to obtain the cathode sensitivity distribution of the photoelectric cathode of the photomultiplier to be tested and the information of the thickness of the photoelectric cathode film layer.

[0030] The present invention provides a device and method for measuring a photomultiplier photoelectric cathode. It has the following beneficial effects:

[0031] 1. By adopting the technical solution of synchronously measuring the photoelectric cathode film layer and the cathode sensitivity, the present invention can obtain the corresponding relationship between the two in real time in the same test process. Compared with the prior art of separately and independently testing the film layer thickness and the cathode sensitivity, it effectively solves the problems of low measurement efficiency and poor correlation of test data, and improves the integrity and accuracy of the performance evaluation of the photoelectric cathode.

[0032] 2. The present invention constructs a local illumination system composed of a drive circuit, an optical fiber, and a sensing head, and cooperates with the real-time acquisition mechanism of a microammeter and a beam splitter, enabling the synchronous acquisition of optoelectronic signals and interference optical signals, and realizing the joint analysis of the electrical performance of the photocathode and the film structure. Compared with the prior art in which the testing means are scattered and the feedback is lagging, the testing process of the present invention is more compact and the response is faster, and it can provide more targeted process monitoring and data support for the improvement of the photocathode process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the device architecture of the present invention;

[0034] Figure 2 is a diagram of the test results of the device of the present invention;

[0035] Figure 3 is a flowchart of the method steps of the present invention.

[0036] Among them, 1. Light source; 2. Drive circuit; 3. Collimator; 4. Optical fiber; 5. Dark box; 6. Sensing head; 7. Moving platform; 8. Fixture; 9. Low-voltage source; 10. Microammeter; 11. Beam splitter; 12. Computer and acquisition software. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Embodiment 1:

[0039] Please refer to the attached Figure 1 - attached Figure 2 , the embodiment of the present invention provides a measuring device for a photomultiplier photocathode, including:

[0040] A light source assembly, which is used as the enabling condition for device driving and is used to emit measurement light;

[0041] The collimator 3, which is arranged on one side of the light source assembly and is used to collimate the light emitted by the light source assembly;

[0042] The optical fiber 4, which is arranged at the rear end of the collimator 3 and is used to transmit the light emitted by the collimator 3;

[0043] The dark box 5, which is arranged on one side of the collimator 3 and is used to shield ambient light stray light and low-frequency magnetic fields;

[0044] A sensing head 6, which is arranged inside the dark box 5 and is connected to the right port of the collimator 3 far from the optical fiber 4, is used to output the light in the optical fiber 4 and input the reflected light to generate interference light, and then transmit it back through the optical fiber 4;

[0045] A fixing component, which is arranged inside the dark box 5, is used to fix the photomultiplier tube to be tested and enable it to move in a two-dimensional plane;

[0046] A low-voltage source 9, which is connected to the input end of the photomultiplier tube to be tested, is used to transmit the light reflected by the photomultiplier tube to be tested to the optical fiber 4;

[0047] A microammeter 10, whose input end is connected to the cathode output end of the photomultiplier tube to be tested through a wire;

[0048] A spectroscope 11, which is connected to the bottom port of the optical fiber 4, is used to split the interference light in the optical fiber 4 to obtain a spectrogram;

[0049] A computer and acquisition software 12, whose input ends are respectively connected to the spectroscope 11 and the microammeter 10, and are connected to the low-voltage source 9 through the output end, is used to process and analyze the information of the photomultiplier tube to be tested obtained;

[0050] The light source assembly includes a light source 1 and a drive circuit 2. The rear end of the drive circuit 2 is connected to the collimator 3, and the light source 1 and the drive circuit 2 are electrically connected;

[0051] The fixing component includes a moving platform 7 and a fixture 8. The moving platform 7 is arranged inside the dark box 5. The moving platform 7 and the fixture 8 are connected by bolts, and the fixture 8 and the sensing head 6 are vertically distributed;

[0052] The light source 1 includes a white light diode, a green light diode and a blue light diode, and the central wavelength of the light source 1 is 390nm - 420nm;

[0053] The inside of the collimator 3 includes two groups of vacuum diaphragms, and they are both 5um - 100um;

[0054] The distance between the collimator 3 and the photomultiplier tube to be tested is 10mm - 50mm;

[0055] The dark box 5 is filled with permalloy and the inside is painted black;

[0056] The voltage range of the low-voltage source 9 is 0V - 500V;

[0057] The sensitivity of the microammeter 10 is 10 -12 -10 -15 A.

[0058] Specifically, before the test operation, the photomultiplier tube to be tested needs to be firmly installed on the moving platform 7 through the fixture 8; the fixture 8 ensures that the tube body does not shake during the test, and at the same time, through the drive of the moving platform 7, the photocathode can be accurately positioned and moved point by point in the two-dimensional plane, which helps to comprehensively collect the performance data of different regions and improve the accuracy of the sensitivity distribution analysis;

[0059] After the positioning is completed, the operator initializes and sets the test parameters through the computer and the acquisition software 12, including the position of the collimator 3, the step size and the scanning range of the moving platform 7, and the loading voltage of the low-voltage source 9, etc.; among them, the voltage range of the low-voltage source 9 is 0V to 500V, which can be flexibly adjusted according to the characteristics of different photomultiplier tubes to ensure the stability of the test electric field and effectively simulate the actual working state;

[0060] After the drive circuit 2 is started, the light source 1 starts to emit test light; the light source 1 can be a white light diode, a green light diode or a blue light diode, and preferably a blue light source with a wavelength between 390nm and 420nm, because its response efficiency on most photocathode materials is higher, which can improve the test sensitivity and imaging clarity;

[0061] The emitted light first enters the collimator 3, and there are two groups of vacuum diaphragms with a size of 5μm to 100μm inside, which are used to accurately limit the beam diffusion range and achieve high-quality parallel light output; this collimation structure ensures the consistency of the incident light direction, improves the illumination uniformity, and avoids the influence of spot defocus on the test data; at the same time, the distance between the collimator 3 and the photomultiplier tube to be tested is designed to be 10mm to 50mm, and after optimization and matching, it takes into account both the spot coverage range and the focusing accuracy;

[0062] The collimated light is transmitted to the sensing head 6 through the optical fiber 4, and the sensing head 6 performs secondary focusing on the light beam and then irradiates it on the surface of the photocathode; this local irradiation method can realize the micro-area excitation of any position of the photocathode and accurately obtain the local response data, which has a higher spatial resolution compared with the traditional overall irradiation method;

[0063] After the photocathode responds to the light excitation to generate a photocurrent, this electrical signal is collected by a high-sensitivity microammeter 10, and its measurement sensitivity can reach 10 -12 A to 10 -15 A, which can accurately capture the weak signal changes and ensure the stability and reliability of the test data; the collected current data is transmitted to the computer and the acquisition software 12 in real time for recording and processing to obtain the sensitivity distribution map of the photocathode;

[0064] Meanwhile, a part of the light is reflected by the surface of the photocathode during irradiation and enters the optical fiber 4 again to form an interference optical signal; the interference light is processed by the optical splitter 11 to generate an optical intensity spectrogram for analyzing optical characteristics such as film thickness; the reflection interference method can extract the film structure information without damaging the tube structure, making up for the deficiency of traditional testing that requires disassembling the device;

[0065] The entire measurement process is carried out in the dark box 5. The dark box 5 is filled with permalloy and coated with a black light-absorbing layer on the inner wall, which can effectively shield environmental stray light and low-frequency magnetic field interference, providing a stable and low-noise enclosed space for testing;

[0066] Finally, both the photoelectric signal and the spectral data are transmitted to the computer and the acquisition software 12 for joint processing, so as to synchronously obtain the film thickness information of the photocathode and the spatial distribution of the cathode sensitivity, realizing the accurate evaluation of the two parameters; this method greatly improves the test efficiency and data consistency, providing key data support for the process control and performance improvement of the photocathode.

[0067] Embodiment 2:

[0068] Please refer to the attached Figure 3 , a measurement method for the photocathode of a photomultiplier tube, comprising the following steps:

[0069] S1. Fix the photomultiplier tube to be measured on the moving platform 7 with the fixture 8 and close the dark box 5;

[0070] S2. Set the parameters of the collimator 3 in the computer and the acquisition software 12. At the same time, set the step size, moving range, interval time of the moving platform 7 and the loading voltage of the low-voltage source 9. Then start the drive circuit 2 to drive the light source 1 to emit light with a power of milliwatts. After being collimated by the collimator 3, the light enters the optical fiber 4;

[0071] S3. The light entering the optical fiber 4 is converged by the sensing head 6 and irradiates the photocathode surface of the photomultiplier tube to generate a photocurrent, which is collected by the microammeter 10. At the same time, the sensing head 6 also receives the light reflected from the photomultiplier tube to be measured and transmits it into the optical fiber 4 to generate interference. The interference light is split by the optical splitter 11 to obtain an optical intensity spectrogram;

[0072] S4. According to the computer and the acquisition software 12 set in step S2, the current value is collected from the microammeter 10 and the optical intensity spectrogram is collected from the optical splitter 11 at this time, and then they are processed and analyzed to obtain the cathode sensitivity distribution of the photocathode of the photomultiplier tube to be tested and the photocathode film thickness information.

[0073] Specifically, the specific effect of the test method in this Embodiment 2 is the same as that of the solution and Embodiment 1, and will not be elaborated here.

[0074] Working principle: Before measurement, the photomultiplier tube to be tested needs to be fixed with the fixture 8 so that it can move along with the moving platform 7. After the fixation is completed, the parameters of the collimator 3, the moving platform 7 and the low-voltage source 9 are set through the computer and the acquisition software 12. After the parameter setting is completed, the light source 1 is turned on through the drive circuit 2. At this time, the light source 1 starts to emit light. The emitted light will first be collimated at the position of the collimator 3 and then enter the optical fiber 4 for transmission. At this time, the light will first pass through the position of the sensing head 6, be converged by it, and irradiate the cathode position of the photomultiplier tube to generate a photocurrent, which is collected by the microammeter 10 and the data is transmitted into the computer and the acquisition software 12. Moreover, when the light is irradiating, due to the reflection problem, the light will be re-transmitted into the optical fiber 4 to generate interference light. The interference light undergoes a splitting operation through the beam splitter 11 to form an optical intensity spectrogram. Finally, the data is transmitted into the computer and the acquisition software 12 and processed and analyzed together with the data transmitted by the microammeter 10 to obtain the cathode sensitivity distribution of the photocathode of the photomultiplier tube to be tested and the information on the thickness of the photocathode film layer.

[0075] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for measuring a photocathode of a photomultiplier tube, characterized in that: include: A light source component, which is used as an enabling condition for the device driver to emit light for measurement; A collimator (3), which is arranged on one side of the light source assembly and is used to collimate the light emitted by the light source assembly; An optical fiber (4), which is arranged at the rear end of the collimator (3) and is used to transmit the light emitted by the collimator (3); A dark box (5), which is arranged on one side of the collimator (3) and is used to shield ambient light, stray light and low-frequency magnetic field; A sensor head (6) is arranged inside the dark box (5) and connected to the right port of the optical fiber (4) away from the collimator (3), and is used to generate interference light between the light in the output optical fiber (4) and the input reflected light, and transmit it back through the optical fiber (4); A fixing assembly, which is arranged inside the dark box (5) and is used to fix the photomultiplier tube to be tested and enable it to move in a two-dimensional plane; A low-voltage source (9) is connected to the input end of the photomultiplier tube to be tested and is used to transmit the light reflected by the photomultiplier tube to be tested to the optical fiber (4); A microammeter (10), the input end of which is connected to the cathode output end of the photomultiplier tube to be tested through a wire; A spectrometer (11) connected to the bottom port of the optical fiber (4) and used for splitting the interference light in the optical fiber (4) to obtain a spectrum; The computer and acquisition software (12) are respectively connected to the spectrometer (11) and the micro-ammeter (10) at their input ends, and are connected to the low-voltage source (9) via their output ends, for processing and analyzing the obtained information of the photomultiplier tube to be tested.

2. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The light source assembly comprises a light source (1) and a driving circuit (2); the rear end of the driving circuit (2) is connected to a collimator (3); and the light source (1) and the driving circuit (2) are electrically connected.

3. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The fixing assembly comprises a moving platform (7) and a clamp (8); the moving platform (7) is arranged inside the dark box (5); the moving platform (7) and the clamp (8) are connected via bolts; and the clamp (8) and the sensor head (6) are arranged in a vertical state.

4. The device for measuring the photocathode of a photomultiplier tube according to claim 2, characterized in that: The light source (1) comprises a white light diode, a green light diode and a blue light diode, and the central wavelength of the light source (1) is 390nm-420nm.

5. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The collimator (3) includes two groups of vacuum apertures inside, both of which are 5um-100um.

6. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The distance between the collimator (3) and the photomultiplier tube to be measured is 10 mm-50 mm.

7. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The dark box (5) is filled with Permalloy, and the interior is completely painted black.

8. The device for measuring the photocathode of a photomultiplier tube according to claim 1, characterized in that: The voltage range of the low voltage source (9) is 0V-500V; The sensitivity of the microammeter (10) is 10 -12 -10 -15 A.

9. A method for measuring a photomultiplier tube photocathode, according to a device for measuring a photomultiplier tube photocathode according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, fix the photomultiplier tube to be tested on the moving platform (7) with a fixture (8), and close the dark box (5); S2, setting the parameters of the collimator (3) in the computer and the acquisition software (12), and setting the step size, moving range, interval time of the moving platform (7) and the loading voltage of the low-voltage source (9), and then starting the driving circuit (2) to drive the light source (1) to emit light with a power of milliwatts, which enters the optical fiber (4) after being collimated by the collimator (3); S3, the light entering the optical fiber (4) is converged by the sensor head (6), irradiated on the photocathode surface of the photomultiplier tube to generate photocurrent, and collected by the microammeter (10). At the same time, the sensor head (6) also receives the light reflected from the photomultiplier tube to be tested, and transmits it to the optical fiber (4) to generate interference. The interference light is split by the spectrometer (11) to obtain a light intensity spectrum. S4. The computer and acquisition software (12) set up according to step S2 will collect the current value from the microammeter (10) and the light intensity spectrum from the spectrometer (11), and then process and analyze them to obtain the cathode sensitivity distribution of the photocathode of the photomultiplier tube to be tested and the photocathode film thickness information.

10. The method for measuring the photocathode of a photomultiplier tube according to claim 9, characterized in that: Before measuring, the photomultiplier tube to be measured needs to be fixed with a clamp (8) so that it can move with the mobile platform (7). After the fixing is completed, the parameters of the collimator (3), the mobile platform (7) and the low-voltage source (9) are set through the computer and the acquisition software (12). After the parameter setting is completed, the light source (1) 1 is adjusted to the on state through the driving circuit (2). At this time, the light source (1) starts to irradiate light. The irradiated light will first pass through the position of the collimator (3) for collimation, and then enter the optical fiber (4) for transmission. At this time, the light will first pass through the position of the sensor head (6) and be converged through it. , irradiated to the cathode position of the photomultiplier tube to generate photocurrent, which is collected by the microammeter (10) and the data is transmitted to the computer and the collection software (12). In addition, while the light is irradiated, due to the reflection problem, the light is retransmitted to the optical fiber (4) through reflection to generate interference light. The interference light is split by the spectrometer (11) to form a light intensity spectrum. Finally, the data is transmitted to the computer and the collection software (12) and processed and analyzed together with the data transmitted by the microammeter (10) to obtain the cathode sensitivity distribution of the photocathode of the photomultiplier tube to be tested and the photocathode film thickness information.

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