Large-size photomultiplier rotary scanning device and method

Abstract

The invention discloses a large-size photomultiplier tube rotary scanning device, which comprises a rotary scanning platform, a multi-wavelength pulse light source system, a data acquisition system, an intelligent control system and a darkroom environment control system, and is characterized in that the rotary scanning platform is driven by three motors to realize 0.1-degree angular displacement precision and is combined with 9-degree interval distribution of 11 optical fiber interfaces; more than 98% of the area of the PMT cathode surface is covered, and the problem of coverage blind areas of a traditional device is solved. The multi-wavelength light source system provides 350-700nm wide-spectrum ns-level pulsed light, high-precision signal acquisition is realized in cooperation with the continuous optical attenuator and the seven-in-one optical fiber bundle, and data reliability is ensured in combination with fault diagnosis and environmental parameter monitoring of intelligent control. According to the device, through a replaceable supporting module and a longitude-by-latitude line scanning method, the resolution ratio of a two-dimensional response spectrum reaches 0.5 mm / pixel, and key parameters such as gain heterogeneity and the like are effectively evaluated. The invention provides autonomous core equipment for high-energy neutrino detection and cosmic ray origin research, and has remarkable scientific and engineering values.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric conversion, and in particular to a large-size photomultiplier tube rotation scanning device and method. Background Art

[0002] High-energy neutrinos are produced by the interaction of high-energy cosmic rays with matter and radiation within or near their source objects. Because neutrinos are electrically neutral, they are not deflected by magnetic fields in space like cosmic rays, but instead point directly back toward their source. Furthermore, as weakly interacting particles, neutrinos have a very small cross-section for interacting with surrounding particles, allowing them to escape the cores of dense astronomical objects and propagate unimpeded across cosmological distances. Therefore, neutrinos are key messengers in the search for the origins of high-energy cosmic rays. The primary physical objectives of the High-Energy Underwater Neutrino Telescope are to effectively and significantly detect high-energy neutrino sources within the Milky Way, confirm the origin and acceleration mechanism of PeV cosmic rays, explore PeV objects within the Milky Way, identify the origin of ultra-high-energy gamma photons, and provide a definitive answer to the century-old mystery of the origin of galactic cosmic rays. The telescope also aims to achieve a full-sky scan of high-energy neutrino sources above 100 TeV, provide clear constraints on the properties and types of extragalactic neutrino sources, and explore the acceleration process of ultra-high-energy cosmic rays. Photomultiplier tubes (PMTs), the core components of neutrino detectors, convert weak optical signals into electrical signals. While different PMTs are factory-calibrated for performance, we recalibrate them ourselves to ensure they meet experimental requirements due to stability concerns during transportation. Calibration parameters primarily include charge spectrum, time spectrum, gain, time-to-scan (TTS), afterpulse, and nonlinearity.

[0003] At present, the 20-inch photomultiplier tube independently developed by my country is the largest in the world. Since large-sized photomultiplier tubes cannot be simplified into a particle, they will be subject to incident light from various directions and angles during operation. The signals generated by these incident lights are often inconsistent. In order to better restore the incident light information and accurately reconstruct particle events, it is necessary to calibrate the consistency of different positions of the photomultiplier tube. In order to ensure the calibration of different positions, it is necessary to use a point light source to cover the entire cathode surface, which places high demands on the accuracy of the scanning position. Therefore, this application proposes a large-sized photomultiplier tube rotating scanning device. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the present application proposes a large-scale photomultiplier tube rotating scanning device.

[0005] A large-scale photomultiplier tube rotary scanning device includes a rotating scanning frame platform and a multi-wavelength pulse light source system. The rotating scanning frame platform includes a light source switcher, a size-changeable support module, and a scanning frame. The light source switcher includes 12 optical fiber channels, numbered 0 to 11. Each optical fiber channel entrance and exit is equipped with a zoom collimator. A light source switching motor drives a frosted metal sheet to rotate to switch the light-emitting optical fiber. The support module is arranged below the scanning frame and is rotatably and slidably arranged on an optical platform for placing the photomultiplier tube. The scanning frame is equipped with 11 optical fiber interfaces. The scanning frame scans the entire cathode surface of the photomultiplier tube with one rotation. The support module and scanning frame are selected according to the size of the photomultiplier tube.

[0006] The multi-wavelength pulse light source system continuously adjusts within the wavelength range of 350nm-700nm and includes multiple LED modules, a multi-channel programmable pulse driver, and a continuous light attenuator. The LED module integrates a fiber optic signal connector and a fiber optic coupling port. The multi-channel programmable pulse driver has 10 independent channels for driving the LED module to emit light and serving as a trigger signal for the data acquisition system. The continuous light attenuator includes a neutral continuous light attenuation plate, the surface of which is coated with a semi-transparent film with a gradually varying thickness to achieve continuous variation of light transmittance with angle.

[0007] Preferably, it also includes a data acquisition system and an intelligent control system. The data acquisition system collects and stores the photomultiplier tube signal corresponding to each optical fiber position, and performs visualization processing on the collected data signals to obtain the relationship between the various parameter responses of the photomultiplier tube and the incident light intensity and the scanning position; the intelligent control system controls the rotation of the quartz glass attenuation plate on the continuous light attenuator to change the light intensity, controls the rotation of the frosted metal plate on the light source switch to switch the light-emitting optical fiber to realize longitude scanning, and controls the rotation of the scanning frame to realize latitude scanning.

[0008] Preferably, a 1×13 fiber optic splitter is provided at the front end of the light source switcher, and the 12 optical fibers at the outlet of the fiber optic splitter are connected to the 0-11 inlets of the light source switcher, and the 13th optical fiber is used to monitor the stability of the light source; the 0-10 outlets of the light source switcher are connected to the scanning frame through optical fibers, channel 0 corresponds to the zenith angle, channel 10 corresponds to the equatorial position, and channel 11 is vacant.

[0009] Preferably, the multi-wavelength light source system includes a row seat, each row seat is provided with ≤15 LED modules, the LED module is provided with an LED and an optical fiber signal connector inside, and the outside is composed of two upper and lower half shells, one end of which leaks a signal connector for providing a driving pulse, and the other end is a fiber optic port for outputting the coupled light and connecting to the light source switcher.

[0010] Preferably, the continuous optical attenuator further includes a collimation system and a dark chamber, equipped with double aspheric quartz lenses as the collimation system, the neutral continuous optical attenuation sheet is sealed in a black aluminum dark chamber, the center hole is fixed on the stepper motor shaft, and quartz lenses of the optical fiber interface are fixed on both sides of the dark chamber, and the axes of the two quartz lenses coincide.

[0011] Preferably, the neutral continuous light attenuation sheet is made of a quartz glass sheet with a center hole diameter of 10 mm, an outer diameter of 100 mm, and a thickness of 1.0 mm.

[0012] Preferably, the scanning frame is provided with 11 optical fiber interfaces, which are distributed at intervals of 9°, and the angle between the interface axis and the scanning frame rotation axis is 30°±0.5°.

[0013] Preferably, the rotating scanning frame platform also includes a three-degree-of-freedom drive system, which includes an upper rotating motor, a translation slide and a lower rotating motor. The upper rotating motor drives the scanning frame to rotate around the axis to change the angle of illumination; the translation slide enables the support module to move in the horizontal direction, and can scan different positions of the PMT point by point; the lower rotating motor further adjusts the position and angle of the scanning frame, and works in conjunction with the upper rotating motor and the translation slide to achieve three-dimensional scanning of the PMT.

[0014] Correspondingly, a large-size photomultiplier tube rotation scanning method is proposed. The scanning frame and support module of corresponding size are selected according to the size of the photomultiplier tube to be detected. After installation, the initial position is calibrated using a limiter to ensure that the photomultiplier tube is located at the center of the scanning frame with each slide. The photomultiplier tube to be detected is measured using a longitude-by-latitude scanning method. The data acquisition system records the photomultiplier tube signal corresponding to each optical fiber position.

[0015] Preferably, the longitudinal and latitude scanning method comprises the following steps:

[0016] S1. Place the scanning frame in the 0°-180° direction, align the light source switch pointer with port 0, adjust the continuous light attenuator to the minimum transmittance, and adjust the LED voltage and light intensity to make the photomultiplier tube output signal a single photoelectron signal;

[0017] S2: All motors are powered off, optical fiber No. 1 is output, and the response data of the corresponding pole position of the cathode surface of the photomultiplier tube is obtained. After the motors are restored, the optical fibers are switched to optical fibers No. 2 to No. 11 in sequence to achieve latitude-by-latitude scanning from the pole position of a meridian of the cathode surface of the photomultiplier tube to the equator position, thus completing the measurement of a meridian;

[0018] S3, rotating the scanning frame 10° to move the elliptical fiber support to the next meridian, repeating the scanning process of step S2 to complete the measurement of the second meridian, and so on, rotating 10° each time until all meridians are scanned;

[0019] S4. Adjust the continuous light attenuator to increase the intensity of light incident on the cathode surface of the photomultiplier tube. Repeat steps S2 and S3 to complete multiple sets of meridian scans to examine the response changes of the photomultiplier tube under different light intensities.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The precise mechanical design of the rotating scanning platform enables full-area scanning of the cathode surface of ultra-large PMTs (PMTs) measuring 20 inches and larger, with a scanning accuracy of 0.1° angular displacement. Combined with 11 fiber optic interfaces spaced 9° apart, this device enables complete acquisition of response data from the cathode surface. The device innovatively utilizes a three-motor drive system (with a 1:10 speed ratio) and achieves 0.005° position feedback accuracy through closed-loop control, ensuring that the scanning path strictly adheres to spherical coordinate mapping, effectively resolving the coverage blind spots of traditional scanning devices on large devices.

[0022] 2. The multi-wavelength pulse light source system provides 350-700nm wide spectrum adjusted ns-level optical pulses, combined with the 10 -5 to 10 0 The dynamic adjustment range can simulate multiple test scenarios from single photoelectrons to strong light pulses. The multi-channel signal generator of the light source trigger device achieves a time synchronization accuracy of 50ps between channels. Combined with the 95% energy uniformity of the 7-in-1 fiber bundle, it ensures the consistency of optical signals at different locations. The system supports the rapid replacement of 15 LED modules through the row seat structure, significantly improving the efficiency of multi-parameter testing.

[0023] 3. The data acquisition system integrates CAENV792N / QDC and V775N / TDC modules to achieve high-precision signal acquisition with a charge resolution of 0.1pC and a time resolution of 35ps. Combined with the fault self-diagnosis function of the intelligent control system, it can monitor environmental parameters such as temperature, humidity, and air pressure in real time (temperature control accuracy of ±0.5°C) to ensure the reliability of test data. The darkroom environmental control system adopts a double-layer shielding structure (reflectivity <0.1%) and a vacuum balance device to effectively eliminate ambient light interference and support normal pressure / vacuum dual-mode testing. The device is designed with replaceable support modules and is compatible with multiple types of photosensitive probes such as 20 inches / 23 inches / 17 inches / 8 inches, achieving efficient calibration of devices across different sizes. The full parameter test cycle of a single PMT is shortened to less than 3 hours.

[0024] 4. Innovative scanning method of each meridian and each dimension, through three reference point re-measurements and multi-light intensity tests (T=10 -3 , 10 -2 , 10 -1), ensuring data stability deviation ≤2%. The resulting two-dimensional response spectrum (resolution 0.5mm / pixel) can intuitively reflect key parameters such as cathode gain non-uniformity (σ ≤ 5%) and TTS (≤ 1.5ns), providing core technical support for PMT performance optimization and precise calibration of cosmic ray detection equipment. The successful development of this device not only breaks the international technological monopoly on large-scale PMT scanning equipment, but also reduces equipment costs by over 60% through domestic design. It provides independent and controllable core equipment for major scientific projects in my country, such as high-energy neutrino detection and research on the origin of PeV cosmic rays, and is of milestone significance in promoting technological progress in the field of particle astrophysics. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A diagram showing the components of the device of the present invention;

[0026] Figure 2 A schematic diagram of signal transmission between various modules of the device of the present invention;

[0027] Figure 3 Schematic diagram of the mechanical structure of the rotating scanning platform of the present invention (PMT is placed);

[0028] Figure 4 Schematic diagram of the mechanical structure of the rotating scanning platform of the present invention (without PMT);

[0029] Figure 5 This is an operational logic block diagram of the scanning method of the present invention;

[0030] Figure 6 It is a scanning schematic diagram of the present invention;

[0031] Figure 7 Schematic diagram of the scanning results of the present invention.

[0032] Figure numerals: overall frame 1, load-bearing platform 2, upper rotating motor 3, connecting rod 4, scanning frame 5, photomultiplier tube 6, circular support frame 7, first vertical pole 8, support block 9, second vertical pole 10, second support plate 11, first support plate 12, lower rotating motor 13, slider 14, translation rail 15, light source switcher 16, base 17. DETAILED DESCRIPTION

[0033] It should be noted that, unless there is a conflict, the embodiments and features of the embodiments in this application may be combined with each other. This application is further described in detail below with reference to the accompanying drawings and specific embodiments. The specific models of the various devices in this embodiment are merely examples, including but not limited to these models. Other models of devices with the same functionality may also be used.

[0034] Figure 1-4As shown in the figure, an embodiment of the present application provides a large-size photomultiplier tube rotation scanning device, which is composed of a rotation scanning platform, a multi-wavelength pulsed light source system, a data acquisition system, an intelligent control system, and a darkroom environment control system. It is mainly used for comprehensively and highly accurately scanning and testing the performance of large-size photomultiplier tubes (PMTs). It consists of multiple key systems, and each system works in coordination. It can simulate different lighting conditions, accurately collect the response signals of PMTs, and process and analyze the data, providing strong support for the performance evaluation and optimization of PMTs. This device has important application value in fields such as high-energy physics experiments and astronomical observations, and can help researchers better understand the performance characteristics of PMTs and improve the accuracy and reliability of related experiments and observations.

[0035] (1) Rotation scanning platform, including:

[0036] As Figure 3-4 shown in the figure, the rotation scanning platform includes a base 17, a light source switch 1616, a scanning frame 5, and a support module. A "冂"-shaped integral frame 1 is installed on the base 17. A bearing platform 2 is installed on the top of the integral frame 1. An upper rotation motor 3 is installed on the bearing platform 2. A connecting rod 4 is installed at the output end of the upper rotation motor 3. A scanning frame 5 is detachably installed at the end of the connecting rod 4 far from the upper rotation motor 3. Parallel translation slide rails 15 are installed on the base 17 below the scanning frame 5. A matching slider 14 is slidably installed on the translation slide rails 15. A first support plate 12 is installed on the tops of the two sliders 14. A lower rotation motor 13 is installed on the first support plate 12. A second support plate 11 is installed at the output end of the lower rotation motor 13. A support module is installed on the second support plate 11. The support module is arranged below the scanning frame 5. The support module includes a circular support frame 7 and four first vertical rods 8. One end of each first vertical rod 8 is connected to the circular support frame 7, and the other end is connected to the second support plate 11. Four "L"-shaped support blocks 9 are arranged at a distance from the periphery of the circular support frame 7. A second vertical rod 10 is installed at the lower part of each support block 9. The other end of the second vertical rod 10 is connected to the second support plate 11. The light source switch 16 is fixedly installed on the base 17 beside the support module.

[0037] Light source switcher 16. The light source switcher 16 in this embodiment has 12 fiber optic channels, numbered from 0 to 11. The access port of each channel is equipped with a zoom collimator, and its focal length can be adjusted between 5-50mm. This design enables the light source to flexibly adjust the focus of the light beam according to different test requirements to adapt to PMTs of different sizes and characteristics. The frosted metal sheet is driven to rotate by the light source switching motor, and a small through hole is opened on the frosted metal sheet so that only one optical fiber can emit light, realizing the switching function of single optical fiber lighting. In actual use, when different positions of the PMT need to be tested, the light source switcher 16 can quickly switch the luminous fiber optic channel, and the switching time can be controlled within ≤50ms to ensure the high efficiency of the test.

[0038] The front end of the light source switcher 16 is divided into 13 optical fibers from a single optical fiber, which are connected to the light source switcher 16 from the connection board. The optical fiber has a diameter of 1mm and a length of 3m. Twelve of the optical fibers are connected to inlets 0 to 11 of the light source switcher 16, and the 13th is used to monitor the stability of the light source. Inlet ports 0 to 10 are connected to the scanning frame using 11 optical fibers. Channel 0 corresponds to the zenith angle, channel 10 corresponds to the equatorial position, and channel 11 is temporarily vacant. In some specific implementations, the optical fiber beam splitter uses a 1×13 optical fiber splitter made by a fused taper process, with an insertion loss of ≤3dB and an operating wavelength range of 350 to 700nm. The optical fiber beam splitter manufactured by this process has the characteristics of low loss and high stability, which can minimize the energy loss of the light source during transmission while covering a wide wavelength range to meet the wavelength requirements of different experiments.

[0039] The light source switching motor uses a two-phase hybrid stepper motor, model 42BYGH250C, with a step angle of 1.8°. It is coupled with a synchronous belt drive and a transmission ratio of 1:5. This combination precisely controls the rotation angle of the frosted metal plate, ensuring accuracy during each fiber channel switch. Furthermore, the monitoring fiber incorporates an InGaAs photodiode, model PDA10CF-EC, with a responsivity of 0.9A / W at 900nm. This provides real-time monitoring of light source power fluctuations with an accuracy of ±0.1%. This allows for timely detection of changes in light source power during testing, allowing for appropriate adjustments and ensuring accurate test data.

[0040] The three-degree-of-freedom drive system, consisting of an upper rotary motor, a translation slide, and a lower rotary motor, can achieve movement in three directions, thereby performing a comprehensive scan of the PMT.

[0041] The upper rotary motor uses a closed-loop stepper motor, model SM2301C, equipped with a 2500-line incremental encoder. It offers positioning accuracy of ±0.002° and can achieve 360° rotation with a stepping accuracy of 0.1°. In actual testing, the upper rotary motor can drive the scanning gantry to rotate around its axis, precisely changing the angle of illumination to ensure that all angles of the PMT can be scanned.

[0042] The translational slide utilizes a ball screw drive with a 4mm lead, and the slider is equipped with an H-grade linear guide. It has a maximum load capacity of 50kg, a travel range of ±50mm, and a positioning accuracy of 0.01mm. The translational slide enables precise horizontal movement of the support module, enabling point-by-point scanning of different PMT positions, ensuring comprehensive and accurate scanning.

[0043] The lower rotary motor drives the second support plate's overall rotation, with an angular range of 0-360° and a speed ratio of 1:10. An overload protection device is also included, employing a TLL-050 torque limiter with a trigger torque threshold of 15 N·m and a mechanical limit switch accuracy of ±0.02 mm. The lower rotary motor further adjusts the gantry's position and angle, working in conjunction with the upper rotary motor and translational guide rails to achieve three-dimensional scanning of the PMT. The overload protection device promptly cuts off power if the motor load becomes excessive, protecting the motor and equipment. A mechanical limit switch prevents the gantry from exceeding its range of motion, potentially damaging the equipment.

[0044] The support module is designed to accommodate 20-inch, 23-inch, 17-inch, and 8-inch photosensitive probes. This makes the device highly versatile and adaptable to testing PMTs of varying sizes. Stoppers ensure PMT positioning accuracy of ≤0.05mm, ensuring stable and accurate installation of PMTs of varying sizes within the scanner. When switching PMTs of different sizes, simply replace the corresponding support module and use the stoppers for precise positioning, quickly completing test preparation and improving testing efficiency.

[0045] The scanning frame and its elliptical fiber bracket are made of aviation aluminum alloy, grade 6061-T6, CNC-machined and anodized to a thickness of 15μm. Aviation aluminum alloy is characterized by its light weight and high strength. The anodizing treatment improves the surface hardness and corrosion resistance, ensuring the long-term stability and reliability of the scanning frame.

[0046] The scanning frame uses scanning frames of different specifications to accommodate photomultiplier tubes of different sizes. The scanning frame is equipped with 11 SMA905 fiber optic interfaces, each with a 9° angle between them, and a 30°±0.5° angle between the interface axis and the scanning frame's rotation axis. This design allows the optical fiber to illuminate the PMT at specific angles and intervals, thereby more comprehensively covering the PMT's cathode surface. M3×0.5 stainless steel screws are used as the fixing structure, controlling the preload force between 5 and 8 N·m to ensure a fiber head positioning accuracy of ≤5μm. The scanning frame has a single rotation angle of 10°, and one full rotation scans the entire cathode surface. During the test, by precisely controlling the scanning frame's rotation angle and the position of the optical fiber, the PMT's cathode surface can be thoroughly and meticulously scanned, acquiring accurate test data.

[0047] (2) Multi-wavelength pulse light source system, including:

[0048] The wide-spectrum LED module features a continuously adjustable wavelength between 350nm and 700nm. This allows the device to simulate diverse lighting conditions and meet the wavelength requirements of various experiments. In actual testing, researchers can select the appropriate wavelength to test the PMT based on specific experimental requirements, thereby studying its performance characteristics under different wavelengths.

[0049] The wide-spectrum LED module integrates an SMA905 signal connector and a fiber coupling port, and the pulse width can be adjusted between 5ns and 1μs with a step size of 5ns. This design enables the light source to be output in the form of pulses, and the width of the pulse can be precisely controlled. When testing performance indicators such as the response speed of the PMT, by adjusting the pulse width, different light pulse conditions can be simulated, thereby more accurately evaluating the performance of the PMT. Specifically, the wide-spectrum LED module is internally provided with LEDs of different wavelengths and an SMA905 signal connector, both of which are welded on the PCB board. The outside is composed of two half shells, one end of which leaks an SMA connector for providing a driving pulse, and the other end is an SMA fiber port, through which the coupled light is output. The wide-spectrum LED module here can also use other signal connectors. This embodiment is illustrated using the SMA905 signal connector.

[0050] The row mount structure, molded from polyoxymethylene (POM), is designed to accommodate 15 LED modules. POM offers excellent mechanical properties and chemical stability, ensuring stable installation. It is secured to the experimental platform via M6 threaded holes with a ±0.1mm positioning tolerance. The LED modules offer a plug-in / plug-out lifespan of ≥1000 cycles, with replacement time limited to ≤3 minutes. When replacing LED modules with different wavelengths or performance characteristics, operators can quickly and easily make replacements, enhancing experimental flexibility and efficiency.

[0051] A multi-channel programmable pulse driver, used to drive LEDs and serve as a trigger for data acquisition systems, features 10 independent channels. Each channel has independently adjustable pulse width and delay in 5ns increments, with inter-channel jitter less than 50ps. The output amplitude ranges from 0V to 6.6V and supports TTL / CMOS levels. The driver integrates an IRF740 high-speed FET switch with rise / fall time lags of ≤5ns and inter-channel crosstalk of ≤-60dB. This multi-channel programmable pulse driver precisely controls the pulse output of each LED module, ensuring signal synchronization and independence between channels. In actual testing, by varying the output amplitude and pulse width, light pulses of varying intensities and timing characteristics can be simulated, enabling more comprehensive performance testing of the PMT.

[0052] The core components of a continuous optical attenuator are a neutral continuous optical attenuator and a deceleration stepper motor that drives the attenuator. The attenuator is made from a customized quartz glass attenuator with a center hole diameter of 10mm, an outer diameter of 100mm, and a thickness of 1.0mm. A semi-transparent film with a gradient thickness is applied to the surface of the quartz glass attenuator to achieve a continuous change in light transmittance with angle. The gradient semi-transparent film is produced using electron beam evaporation, with a thickness gradient of 0.1 to 5μm and a uniformity of ±5%. This design enables the continuous optical attenuator to continuously and precisely adjust the intensity of the light source. When testing performance indicators such as the linear response of a PMT, the attenuation rate of the continuous optical attenuator can be adjusted to vary the intensity of the light, thereby studying the PMT's response characteristics under varying light intensities.

[0053] Equipped with dual aspheric quartz lenses as the collimation system, the focal length is 100mm, the aperture is 25mm, and the wavefront aberration is ≤λ / 4@633nm. The collimation system can collimate the light emitted by the light source, improving the parallelism of the light and ensuring the uniformity and accuracy of the lighting. The inner wall of the darkroom structure is coated with matte black paint, model AC-110, with a reflectivity of <0.5% and light leakage ≤1μW / cm 2 Driven by a stepper motor, the attenuation rate can be changed from 10 -5 to 10 0 The continuous adjustment of light intensity uniformity error is ≤3%. The dark chamber structure can effectively reduce the interference of external light and ensure the stability and accuracy of the test environment.

[0054] Specifically, the light attenuation plate is sealed within a black aluminum dark chamber, with its center hole fixed to the stepper motor shaft. Quartz lenses with SMA905 interfaces are fixed on either side of the dark chamber, with their axes coinciding. During the test, a host computer controlled the multi-channel programmable pulse driver channels via a USB-RS232 communication line. Each channel was used to trigger different LEDs: Channel 1 generated the synchronous gating signal for the QDC, and Channel 2 generated the synchronous gating signal for the TDC. The host computer controlled the output voltage of the multi-channel programmable pulse driver and the number of rotations of the stepper motor. The pulsed light emitted by the LED was output via a 7-in-1 optical fiber. After attenuation by a continuous optical attenuator, the output light was output from the optical fiber to a collimator, which then irradiated the light pulses onto the PMT photocathode.

[0055] This multi-wavelength pulsed light source system, with a wavelength range of 350nm-700nm, can provide different wavelengths for different application scenarios. A multi-channel programmable pulse driver precisely controls pulse width and interval, enabling multi-parameter, batch, and automated testing of photomultiplier tubes. Detailed testing of multi-wavelength light sources, including LED spectrum, luminous duration, luminous intensity, and luminous stability, is possible. The pulsed light source delivers light pulses with nanosecond-level temporal resolution, and the driver precisely controls pulse width and interval.

[0056] (3) Data collection system, including:

[0057] The CAEN chassis includes an external power supply box and various internal component plug-ins. The power supply box consists of 8 VME slots on the left and 5 NIM slots on the right. There are 9 plug-ins inserted inside. Their specific parameters are shown in Table 1.

[0058] Table 1 Plug-in detailed parameters

[0059] Plugin Name Detailed parameters N979 16 channels, magnification 2, 4, 6, 8, 10 DT8033m 8-channel high-voltage power supply, 4kV / 3mA (max 6W) N978 4 channels, ×10 adjustable gain N841 16-channel leading edge discriminator, threshold -1mV to -255mV V859 Passive dual-section attenuator, dual 0 to 44.5dB, single 0 to 89dB V1743 16-channel 12-bit 3.2GS / s ADC V775N 16-channel TDC, LSB 35 to 300ps V792N 16-channel QDC, LSB 100fC V3718 VME to USB 2.0 / Optical Link Bridge

[0060] The CAENDT8033 independent power supply module features 8 channels of ±4kV output, a ripple factor of <0.01%, and supports remote high-voltage adjustment. In actual testing, this power supply module provides stable high-voltage power to the PMT, ensuring its proper operation. The low ripple factor ensures power supply stability and reduces the impact of power supply fluctuations on test data. The remote high-voltage adjustment function allows operators to adjust the power supply output voltage without having to touch the high-voltage equipment, improving operational safety.

[0061] The VME / NIM hybrid chassis integrates a QDC, TDC, and waveform digitizer plug-in. The QDC utilizes the CAENV792N analog-to-digital converter, which offers 14-bit resolution, a sampling rate of 100 MS / s, and a dynamic range of ±10V. The QDC precisely measures the charge signal output by the PMT. The high resolution and sampling rate ensure accurate and real-time measurements.

[0062] The TDC can be a CAENV775N time-to-digital converter, which has 16 channels, a time resolution of 35 ps, and a measurement range of 0 to 1 μs. The TDC can accurately measure the timing information of the PMT output signal, which is important for studying the PMT's response speed and timing characteristics.

[0063] The waveform digitizer can be the CAENV1742, a 4-channel model with a sampling rate of 250MS / s and a vertical resolution of 12 bits. The waveform digitizer can acquire and analyze the signal waveform output by the PMT, helping researchers understand the signal characteristics and operating status of the PMT.

[0064] The high-voltage terminal block supports bidirectional signal transmission, features impedance matching accuracy of ≤1%, and provides overvoltage protection with a threshold of ±4.2kV. In actual testing, the high-voltage terminal block ensures accurate signal transmission while preventing damage to equipment caused by overvoltage. When the voltage exceeds the threshold, the terminal block automatically disconnects the circuit, protecting equipment and personnel.

[0065] (4) Intelligent control systems, including:

[0066] The stepper motor driver, model TMC2209, utilizes closed-loop control, supports microstepping up to 256 subdivisions, and has a current adjustment range of 0.1 to 2.5A. Closed-loop control monitors the stepper motor's position and status in real time, ensuring accurate and stable motion. The microstepping function further refines the motor's step angle, improving its accuracy. In actual testing, precise control of the stepper motor's motion enables precise position control of the scanning gantry, ensuring scanning accuracy.

[0067] The host computer software, developed based on JavaFX, supports multi-threaded control, dynamically adjusts thread priorities, and maintains an interface response time of ≤100ms. The software supports USB-RS232 / RS485 dual communication modes for multi-threaded task scheduling. The host computer software provides centralized control and management of the entire scanning device, allowing operators to set various parameters such as stepper motor motion parameters, light source wavelength and pulse width, and data acquisition parameters. Multi-threaded control and task scheduling capabilities improve system efficiency, while the short interface response time ensures a smooth user experience.

[0068] The Data Visualization Module generates a two-dimensional (2D) response map of the PMT cathode surface with a resolution of 0.5 mm / pixel and an error analysis accuracy of ≤0.5%. The Data Visualization Module displays collected PMT response data as an intuitive 2D map, allowing researchers to quickly understand the response of the PMT cathode surface and identify potential problems and anomalies. The high error analysis accuracy ensures the accuracy and reliability of the map, providing researchers with more valuable information.

[0069] The data storage module utilizes a solid-state drive array with a data write speed of ≥500MB / s and a redundant backup cycle of ≤1 hour. This array can quickly store large amounts of collected data, ensuring data integrity and security. The redundant backup function prevents data loss and ensures the reliability of experimental data.

[0070] (5) Darkroom environmental control system, including:

[0071] The light-shielded chamber features a double-layer structure: a 5mm-thick inner layer of black plexiglass and an outer layer of 2mm-thick cold-rolled steel. Silicone seals are used at the seams. This design effectively blocks interference from external light, providing a dark, stable environment for PMT testing. During actual testing, the light-shielded chamber prevents the PMT from being affected by external light, ensuring accurate test data.

[0072] The temperature control system is equipped with a PT100 temperature sensor with an accuracy of ±0.1°C and a TEC1-1 semiconductor cooler with a cooling power of 60W. This system precisely controls and maintains the temperature within the darkroom. During testing, temperature fluctuations can affect PMT performance. This system maintains the temperature within an appropriate range, minimizing the impact of temperature on test results.

[0073] Air pressure balance device, equipped with a diaphragm vacuum pump, model MVP015, with an ultimate vacuum degree of 1×10 -3mbar, and the solenoid valve response time is ≤50ms. The pressure balance device maintains a stable pressure within the darkroom, preventing pressure fluctuations from affecting the PMT's performance. In actual testing, pressure fluctuations can cause changes in the gas state within the PMT, affecting its performance. The pressure balance device keeps the pressure within an appropriate range, ensuring accurate test results.

[0074] It should be noted that the darkroom environment control system does not need to be equipped with a separate temperature control system and air pressure balance device. The detector to be tested can be used. In this case, the darkroom is mainly controlled by an external air conditioner.

[0075] like Figure 5-6 As shown, the present invention also provides a method for using a large-size photomultiplier tube rotating scanning device, the method comprising:

[0076] First, based on the size of the large-size photomultiplier tube to be scanned, a suitable support module and scanning frame are selected and installed on the rotating scanning platform. After installation, the initial position is calibrated using a limiter so that each slide can place the PMT in the center of the scanning frame, ensuring that the PMT positioning accuracy is ≤0.05mm, thereby ensuring the stability and accuracy of the PMT during the scanning process.

[0077] Start the darkroom environment control system, close the light shielding cabin, and ensure a good seal with silicone sealing strips. Turn on the temperature control system and set the appropriate temperature according to the test requirements. Use the PT100 temperature sensor to monitor the temperature changes in real time and use the semiconductor cooler to control the temperature within an accuracy of ±0.1°C. At the same time, start the air pressure balance device and use the diaphragm vacuum pump to pump the air pressure in the darkroom to the appropriate range, with the ultimate vacuum reaching 1×10-3 m bar, using the solenoid valve to quickly respond and adjust the air pressure to ensure stable air pressure.

[0078] Enable the intelligent control system and set various parameters using the host computer software. For the stepper motor driver, set the stepper motor's displacement accuracy to ±0.01mm and select the appropriate motion mode and speed based on the test requirements. For the optical attenuator, set the initial attenuation rate and continuously adjust it based on the experimental requirements. For the fiber optic switcher, set the switching mode and interval to ensure that each switching time is ≤50ms.

[0079] Start the multi-wavelength pulse light source system and select the appropriate LED module according to the experimental requirements. The LED module can be quickly replaced through the row seat structure, and the replacement time is controlled within 3 minutes or less. Adjust the wavelength of the wide-spectrum LED module so that it can be continuously adjusted between 350nm-700nm, and set the pulse width between 5ns and 1μs with a step size of 5ns. Control the light source output through a multi-channel programmable pulse driver, set the output amplitude between 0V-6.6V, and the time jitter between channels is <50ps to ensure the signal synchronization and independence between each channel. Use a continuous optical attenuator to accurately adjust the light intensity to achieve an attenuation rate from 10 -5 to 10 0 Continuous adjustment of light intensity uniformity error ≤ 3%.

[0080] The light source switcher 16 switches optical fiber channels according to a set program, with each switching time ≤50ms, achieving single-fiber illumination. Simultaneously, the monitoring fiber monitors light source power fluctuations in real time with an accuracy of ±0.1%. If power fluctuations exceed the allowable range, timely adjustments are made to ensure light source stability.

[0081] The three-degree-of-freedom drive system operates according to control commands. The upper rotary motor rotates 360° with a step accuracy of 0.1°. Through closed-loop control and a 2500-line incremental encoder, positioning accuracy reaches ±0.002°, driving the scanning gantry to rotate around its axis, changing the angle of illumination. The translational slide moves horizontally with a travel range of ±50mm and a positioning accuracy of 0.01mm. A ball screw drive and H-grade linear guide ensure accurate and stable movement. The lower rotary motor drives the entire support plate, with an angular range of 0-360° and a speed ratio of 1:10. Working in conjunction with the upper rotary motor and translational slide, it achieves three-dimensional scanning of the PMT. The scanning gantry rotates 10° at a time, gradually covering more than 98% of the cathode surface.

[0082] The data acquisition system simultaneously collects the PMT output signal. A CAENDT8033 independent power supply module provides the PMT with a stable ±4kV high-voltage power supply with a ripple factor of <0.01% and supports remote high-voltage adjustment. A QDC measures the PMT output charge signal with a charge resolution of 0.1pC. This data is acquired via a CAENV792N analog-to-digital converter at a sampling rate of 100MS / s and a dynamic range of ±10V. A TDC records the timing information of the PMT output signal with a time resolution of 50ps. This data is measured on 16 channels using a CAENV775N time-to-digital converter, with a measurement range of 0 to 1μs. A waveform digitizer acquires the signal waveform using a CAENV1743 waveform digitizer, sampling at a 3.2GS / s rate on four channels with a vertical resolution of 12 bits. The acquired data is transmitted to the intelligent control system via a high-voltage terminal block, which supports bidirectional signal transmission, has an impedance matching accuracy of ≤1%, and provides overvoltage protection with a trip threshold of ±4.2kV.

[0083] An intelligent control system processes and analyzes the collected data. A stepper motor driver precisely controls the stepper motor's motion, ensuring scanning accuracy. The host computer software efficiently processes the collected data through multi-threaded control and task scheduling. The data visualization module generates a two-dimensional response map of the PMT cathode surface with a resolution of 0.5 mm / pixel and an error analysis accuracy of ≤0.5%, visually displaying the response of the PMT cathode surface. The data storage module utilizes a solid-state drive array, storing data in real time at a write speed of ≥500 MB / s and a redundant backup period of ≤1 hour to ensure data security and integrity.

[0084] After the scan is complete, shut down all systems. First, shut down the multi-wavelength pulse light source system to stop light output. Then, shut down the data acquisition system to stop data acquisition. Next, shut down the intelligent control system to stop device control and data processing. Finally, shut down the darkroom environmental control system, open the light shielding chamber, and remove the PMT. Clean and maintain the equipment, check the status of all components, and prepare for the next scan.

[0085] In the further implementation process, this embodiment adopts a longitudinal and latitude scanning method to measure the photomultiplier tube to be detected, such as Figure 5 As shown, the specific scanning process is as follows:

[0086] S1. Place the scanning frame in the 0°-180° direction, align the pointer of the light source switch 16 with port 0, adjust the continuous light attenuator to the minimum transmittance, and adjust the LED voltage and light intensity to make the photomultiplier tube output signal a single photoelectron signal;

[0087] S2. Turn off all motors, start the data acquisition system, output fiber 1, obtain the response data of the corresponding photomultiplier tube cathode surface pole position, and after restoring the motors, switch the optical fibers to fibers 2 to 11 in sequence to achieve a latitude-by-latitude scan from the pole position of a meridian of the photomultiplier tube cathode surface to the equator position, completing the measurement of a meridian; to evaluate the system stability, repeat the scan of fiber 1;

[0088] S3, rotating the scanning frame 10° to move the elliptical fiber support to the next meridian, repeating the scanning process of step S2 to complete the measurement of the second meridian, and so on, rotating 10° each time, for a total of 36 scans, until all meridians are scanned; scan the first meridian again for the final evaluation of system stability;

[0089] After the scan is complete, adjust the continuous light attenuator to increase the intensity of the light incident on the cathode of the photomultiplier tube. Repeat steps S2 and S3 to complete the second and third sets of longitudinal scans to examine the response of the photomultiplier tube under different light intensities. The entire experimental process includes three sets of scans at different light intensities, completing the entire scanning process for one photomultiplier tube.

[0090] During the experiment, the scanning results were as follows Figure 7 As shown in the figure, the data acquisition system records the PMT signal corresponding to each optical fiber position, and finally visualizes the collected data to obtain the relationship between the response of each PMT parameter and factors such as incident light intensity and scanning position.

[0091] In the above test, a multi-channel programmable pulse driver drives an LED. The LED light is connected to the light input port of a continuous optical attenuator via optical fiber. After passing through a quartz glass attenuator, it is connected to a darkroom wiring board via optical fiber and input into the darkroom. An independent power supply is also connected to the wiring board via a high-voltage power cable. The wiring board has a bidirectional connector that is internally connected to the PMT. A computer controls the various motors, adjusts the continuous optical attenuator, light source switcher 16, and scanning frame to their default positions, turns off the darkroom lights, and runs a program on an external computer. The program controls the motors and performs the test according to the above scanning logic. After a set of tests is completed, the scanning frame and support module are replaced with the appropriate size based on the size of the subsequent PMT, and the test is repeated.

[0092] Based on the single photoelectron information obtained from the test, we can test the PMT's operating high voltage, gain and high voltage response curve, single photon spectrum peak-to-valley ratio, TTS, relative quantum efficiency, dark noise count rate, linearity, anode dynode gain ratio, afterpulse rate, etc.

[0093] By replacing scanning frames and support modules of different sizes, spherical scanning tests can be performed on the world's largest purely domestically produced 20-inch photomultiplier tubes or 23-inch optical modules, as well as 17-inch photomultiplier tubes and 8-inch photomultiplier tubes. It is simple to install and operate, and can accurately test the efficiency differences at different positions on the surface of large-size photomultiplier tubes.

[0094] Through the above implementation process, this large-scale photomultiplier tube rotating scanning device can achieve high-precision scanning and performance testing of PMTs of different sizes, providing reliable data support for research and applications in related fields. Furthermore, the coordinated operation and precise control of various systems ensure the efficiency, accuracy, and stability of the testing process.

[0095] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the present application and its equivalents, the present application is intended to include these modifications and variations.

[0096] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various equivalent changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A large-size photomultiplier tube rotating scanning device, characterized by: The system comprises a rotating scanning frame platform and a multi-wavelength pulse light source system. The rotating scanning frame platform includes a light source switcher, a resizable support module, and a scanning frame. The light source switcher includes 12 optical fiber channels, numbered 0 to 11. Each optical fiber channel entrance and exit is equipped with a zoom collimator. A light source switching motor drives a frosted metal sheet to rotate to switch the light-emitting optical fiber. The support module is arranged below the scanning frame and can be rotated and slid on the optical platform to place the photomultiplier tube. The scanning frame is equipped with 11 optical fiber interfaces. The scanning frame scans the entire cathode surface of the photomultiplier tube during one rotation. The support module and scanning frame with appropriate sizes are selected according to the size of the photomultiplier tube. The multi-wavelength pulse light source system continuously adjusts within the wavelength range of 350nm-700nm and includes multiple LED modules, a multi-channel programmable pulse driver, and a continuous light attenuator. The LED module integrates a fiber optic signal connector and a fiber optic coupling port. The multi-channel programmable pulse driver has 10 independent channels for driving the LED module to emit light and serving as a trigger signal for the data acquisition system. The continuous light attenuator includes a neutral continuous light attenuation plate, the surface of which is coated with a semi-transparent film with a gradually varying thickness to achieve continuous variation of light transmittance with angle.

2. The large-size photomultiplier tube rotating scanning device according to claim 1, characterized in that: The system also includes a data acquisition system and an intelligent control system. The data acquisition system collects and stores the photomultiplier tube signal corresponding to each optical fiber position, performs visualization processing on the collected data signal, and obtains the relationship between the response of each parameter of the photomultiplier tube and the incident light intensity and the scanning position; The intelligent control system controls the rotation of the quartz glass attenuation plate on the continuous light attenuator to change the light intensity, controls the rotation of the frosted metal plate on the light source switcher to switch the light-emitting optical fiber to achieve longitude scanning, and controls the rotation of the scanning frame to achieve latitude scanning.

3. The large-size photomultiplier tube rotating scanning device according to claim 1, characterized in that: A 1×13 fiber optic splitter is provided at the front end of the light source switcher. The 12 optical fibers at the outlet of the fiber optic splitter are connected to the 0-11 inlets of the light source switcher, and the 13th optical fiber is used to monitor the stability of the light source; the 0-10 outlets of the light source switcher are connected to the scanning frame through optical fibers, channel 0 corresponds to the zenith angle, channel 10 corresponds to the equatorial position, and channel 11 is vacant.

4. The large-size photomultiplier tube rotating scanning device according to claim 1, characterized in that: The multi-wavelength light source system includes a row seat, each of which is equipped with ≤15 LED modules. The LED module is equipped with an LED and an optical fiber signal connector inside. The outside is composed of two half shells, one end of which leaks a signal connector for providing a driving pulse, and the other end is an optical fiber port for outputting coupled light and connecting to a light source switcher.

5. The large-size photomultiplier tube rotating scanning device according to claim 1, characterized in that: The continuous light attenuator also includes a collimation system and a dark chamber. It is equipped with dual aspheric quartz lenses as the collimation system. The neutral continuous light attenuation sheet is sealed in a black aluminum dark chamber. The center hole is fixed on the stepper motor shaft. Quartz lenses with SMA905 interfaces are fixed on both sides of the dark chamber, and the axes of the two quartz lenses coincide.

6. The large-size photomultiplier tube rotating scanning device according to claim 5, characterized in that: The neutral continuous light attenuation sheet is made of a quartz glass sheet with a center hole diameter of 10 mm, an outer diameter of 100 mm, and a thickness of 1.0 mm.

7. The large-size photomultiplier tube rotating scanning device according to claim 6, characterized in that: The scanning frame is provided with 11 optical fiber interfaces, which are distributed at intervals of 9 degrees, and the angle between the interface axis and the scanning frame rotation axis is 30 degrees ± 0.5 degrees.

8. The large-size photomultiplier tube rotating scanning device according to claim 7, characterized in that: The rotating scanning frame platform also includes a three-degree-of-freedom drive system, which includes an upper rotating motor, a translation slide and a lower rotating motor. The upper rotating motor drives the scanning frame to rotate around the axis to change the angle of illumination; the translation slide enables the support module to move in the horizontal direction, and can scan different positions of the PMT point by point; the lower rotating motor further adjusts the position and angle of the scanning frame, and works in conjunction with the upper rotating motor and the translation slide to achieve three-dimensional scanning of the PMT.

9. A large-size photomultiplier tube rotation scanning method, characterized by: According to the size of the photomultiplier tube to be tested, a scanning frame and support module of corresponding size are selected. After installation, the initial position is calibrated using a limiter to ensure that the photomultiplier tube is located in the center of the scanning frame with each slide. The photomultiplier tube to be tested is measured using a longitude-by-latitude scanning method, and the data acquisition system records the photomultiplier tube signal corresponding to each optical fiber position.

10. The large-size photomultiplier tube rotation scanning method according to claim 9, characterized in that: The method for scanning latitude by latitude and longitude comprises the following steps: S1. Place the scanning frame in the 0°-180° direction, align the light source switch pointer with port 0, adjust the continuous light attenuator to the minimum transmittance, and adjust the LED voltage and light intensity to make the photomultiplier tube output signal a single photoelectron signal; S2: All motors are powered off, optical fiber No. 1 is output, and the response data of the corresponding pole position of the cathode surface of the photomultiplier tube is obtained. After the motors are restored, the optical fibers are switched to optical fibers No. 2 to No. 11 in sequence to achieve latitude-by-latitude scanning from the pole position of a meridian of the cathode surface of the photomultiplier tube to the equator position, thus completing the measurement of a meridian; S3, rotating the scanning frame 10° to move the elliptical fiber support to the next meridian, repeating the scanning process of step S2 to complete the measurement of the second meridian, and so on, rotating 10° each time until all meridians are scanned; S4. Adjust the continuous light attenuator to increase the intensity of light incident on the cathode surface of the photomultiplier tube. Repeat steps S2 and S3 to complete multiple sets of meridian scans to examine the response changes of the photomultiplier tube under different light intensities.

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