CN111537855A

CN111537855A - Highly-automatic photomultiplier performance testing device and testing method

Info

Publication number: CN111537855A
Application number: CN202010551678.4A
Authority: CN
Inventors: 李澄; 江琨; 唐泽波; 李昕; 赵晓坤; 唐逸敏
Original assignee: University of Science and Technology of China USTC
Current assignee: University of Science and Technology of China USTC
Priority date: 2020-06-16
Filing date: 2020-06-16
Publication date: 2020-08-14

Abstract

A photomultiplier performance test device comprises a camera bellows, a light source system, a high-voltage system, an electronics system and a data acquisition and control system; the camera bellows is used for providing a light-shading and geomagnetic shielding environment for the photomultiplier to be detected; the light source system is used for providing a light source with a required specific wavelength for the photomultiplier to be detected; the high-voltage system is used for providing required direct-current high voltage for the photomultiplier to be tested; an electronics system for receiving and measuring the output signal of the photomultiplier tube; the data acquisition and control system is used for controlling the type of the photomultiplier testing parameters and the setting of the testing instrument; controlling the luminous intensity and frequency of the light source system; controlling and monitoring the high voltage and current provided by the high voltage system to the photomultiplier; providing a gate signal, a trigger signal and a reference time for the electronics system; reading measurement data of an electronic system; and calling analysis software to analyze the test data and obtain test parameters.

Description

Highly-automatic photomultiplier performance testing device and testing method

Technical Field

The invention relates to the technical field of photoelectric detection, in particular to accurate measurement of multi-parameter performance of a high-performance photomultiplier.

Background

The photoelectric sensor is an indispensable device for optical detection, wherein a photomultiplier tube (PMT for short) is widely applied to the fields of optical analysis instruments, cameras, positron annihilation imaging, radioimmunoassay, mass spectrometers, laser scanners, industry, environmental monitoring, national defense and the like, and the technical level of the photoelectric sensor is of great importance to national economy and scientific and technical development.

Particularly in nuclear and particle physical experiments, the high-performance PMT can be used for particle flight time measurement, optical signal detection of a trigger detector, Cerenkov optical detection, photoelectric conversion of an electromagnetic energy device and the like, and has the advantages of wide application, great demand and irreplaceable effect. In such scientific research, it is not enough to refer to the performance parameters provided by the product manual, and how to select high-performance PMT to meet the design requirement is a fundamental problem in development. In practical application, the following test works must be completed:

1) the manufacturer's test standards do not meet the experimental requirements. For example, PMT gain is scaled according to the illumination sensitivity of a standard light source, and the integrated charge amount of a specific light signal of a detector is often used in experiments.

2) The performance of PMT devices of the same model varies somewhat, and manufacturers are unable to provide the exact parameters for each PMT. The experiment requires testing the performance of each PMT device to give the overall performance parameters.

3) The experiment has requirements on PMT specific parameters, and manufacturers cannot provide the PMT, such as: gain non-linearity, post-pulse signal characteristics, dark noise count rate in a particular experimental environment, and the like.

Therefore, a special testing device needs to be established to meet the requirements of scientific experiments on large-scale, rapid and accurate measurement of PMT performance.

A representative prior art solution is a photomultiplier performance testing apparatus developed for experiments in the micro-nuclear reactor in the gulf of california university at los angeles school (UCLA). The experimental device for the microcubes in the Bay is composed of 8 microcubes detectors, a water Cerenkov detector and a resistive plate chamber, wherein the water Cerenkov detector and the resistive plate chamber are wrapped around the 8 microcubes detectors, 2496 large-size (8-inch) low-background PMTs are used for detecting optical signals generated by reaction of the microcubes in the counter electrons and protons, and Cerenkov light generated by background particles in the environment passing through the water Cerenkov detector.

The testing device can measure the performance of 16 PMTs at the same time, and the specific parameters of the measurement comprise: single photon peak, gain, dark noise, front and back pulses, and signal rise and fall times, etc. As shown in fig. 1, for each measurement, a control panel and a data analysis panel of the test platform need to manually click corresponding buttons in the control panel for multiple times to perform data acquisition and data analysis until the measurement of all parameters is completed.

The above prior art has the following problems:

1) in the prior art, the PMT performance can be measured manually item by item only, and the automation degree needs to be further improved. After each measurement is finished, the button needs to be manually clicked to perform data analysis, and after the data analysis is finished, the button needs to be manually clicked to perform the next measurement. The measurement time and labor cost are increased, and the performance detection of the PMT in large batch is not facilitated.

2) Because PMT in the microelectron experiment in the Bay of great asia only reads out signals from the anode, the existing measuring device can only read out and analyze anode signals, and has no module for reading out and analyzing dynode signals. In many applications, however, to extend the PMT linear dynamic range of readout, it is often necessary to read out the signal from the PMT anode and dynode simultaneously, which requires the test system to be able to read out and analyze the dynode signal.

3) The prior art measures the post pulse by using a charge-to-digital converter (QDC) to measure the charge amount of the post pulse within a certain time window, and the post pulse ratio is the ratio of the charge amount of the post pulse to the charge amount of the main pulse. This technique can measure the total post-pulse rate within a certain time window, but does not allow to obtain the distribution of the post-pulses over time, i.e. the temporal structure of the post-pulses. In another post-pulse measuring method, a flash-ADC is used for recording the waveform output by the PMT, and the time and the amplitude of the occurrence of the post-pulse are determined through off-line analysis, so that the post-pulse rate is obtained. This technique has two disadvantages. Once, the entire measurement is very time consuming. Taking flash-ADC (CAEN V1729A) as an example, the sampling depth is 2520 points, the sampling frequency is 1GHz, each time window of measurement is only 2.52 microseconds, and the measurement needs to be repeated 6 times to reach the time window above 15 microseconds. Secondly, the amount of stored data is very large. Hundreds of thousands of waveforms (e.g., 5 thousands of waveforms multiplied by 6 times per time window) need to be recorded in full for off-line processing analysis, which is a large amount of data and time consuming analysis.

Disclosure of Invention

Accordingly, the present invention is directed to a highly automated photomultiplier tube performance testing apparatus and method, which are used to solve at least one of the above problems.

In order to achieve the above object, as an aspect of the present invention, there is provided a photomultiplier tube performance testing apparatus, including a dark box, a light source system, a high voltage system, an electronics system, and a data acquisition and control system; wherein the content of the first and second substances,

the camera bellows is used for providing a light-shading and geomagnetic shielding environment for the photomultiplier to be detected;

the light source system is used for providing a light source with a required specific wavelength for the photomultiplier to be detected;

the high-voltage system is used for providing required direct-current high voltage for the photomultiplier to be tested;

an electronics system for receiving and measuring the output signal of the photomultiplier tube;

the data acquisition and control system is used for controlling the type of the photomultiplier testing parameters and the setting of the testing instrument; controlling the luminous intensity and frequency of the light source system; controlling and monitoring the high voltage and current provided by the high voltage system to the photomultiplier; providing a gate signal, a trigger signal and a reference time for the electronics system; reading measurement data of an electronic system; and calling analysis software to analyze the test data and obtain test parameters.

Wherein the optical fiber, the high-voltage cable and the signal cable in the camera bellows pass through the camera bellows to be connected with an external instrument.

Wherein, when the camera shelter door is opened, the high-voltage power supply can be automatically cut off.

The light source system comprises an LED, a picosecond laser, a light mixing splitter and an outgoing optical fiber; the light generated by the LED and the picosecond laser is LED out by a plurality of optical fibers through the light mixing and splitting device, the optical fibers penetrate through the dark box, the size of each optical fiber spot is adjustable, and all photocathodes of a single photomultiplier can be covered.

The light generated by the LED and the picosecond laser is subjected to multiple total reflection in the cylindrical light guide pipe, an optical fiber bundle is tightly coupled to the output section of the light guide pipe, 16 output optical fibers at the other end of the optical fiber bundle are connected to an optical fiber interface on the back of the camera bellows in a mutually separated mode, and the relative change ratio of the light intensity output by each optical fiber is 0.9-1.1.

The electronic system comprises a multi-channel signal generator, a gate, an inverter and an amplifier, wherein the signal generator is used for providing multiple paths of outputs, each path of output can be independently switched, each path of output is set to be synchronous with a generator internal clock T0, the frequency of T0 and the delay time of each path of output relative to T0 are adjustable, and the first path of output is used for providing a gate signal and a trigger signal for the electronic system; the second output external trigger signal source can provide two independent outputs to respectively drive the two LEDs to emit light, and the width and amplitude of the drive signal are adjustable; the third path of output triggers the picosecond laser to emit light, and a synchronous output signal generated when the picosecond laser emits light is used as reference time for measuring the dispersion of the transit time of the photomultiplier; the fourth output can provide a reference time for the post-pulse measurement.

The data acquisition and control system comprises a low-threshold discriminator, a scaler, a time-to-digital converter and a charge-to-digital converter.

Wherein each path of the gate has an input and two outputs, wherein one path of the outputs is connected to the second charge-to-digital converter for measuring the linearity of the anode output; the other path of output is connected with a tenfold amplifier for measuring the performance related to the single photon state of the photomultiplier; outputting signals amplified by a tenfold amplifier in a fan-out way, and outputting the signals in a first charge digital converter in a second way, wherein the first charge digital converter is used for measuring a single photoelectron spectrum, energy resolution and detection efficiency; the other path of signal is input into a low-threshold discriminator, and the low-threshold discriminator outputs two paths of discriminating signals: one path of signal is input into a time-to-digital converter and is used for measuring the transit time dispersion and the rear pulse; the other path of signal is input into a scaler for measuring dark noise count; inputting a dynode signal of the photomultiplier into an inverter, and then inputting the dynode signal into a third charge digital converter for measuring the linear range output by the dynode; the second charge-to-digital converter and the third charge-to-digital converter in combination can be used to measure the gain ratio between the anode and the dynode.

As another aspect of the present invention, there is provided a test method using the above photomultiplier tube performance test apparatus, including the steps of:

carrying out test setting according to the type of the measurement parameter;

reading measurement data recorded by an electronic system;

analysis software is invoked to analyze the measurement data.

The measurement parameters comprise stability, single photoelectron spectrum, high-voltage gain curve, single photoelectron spectrum under working gain, peak-to-valley ratio, relative quantum efficiency, transit time dispersion, dark noise and rear pulse;

the structure of the test method program is as follows: the measuring program of each parameter is arranged in the sequential structure of the graphical control software (LabVIEW), so that the measuring program can sequentially measure a plurality of parameters, and the automation degree of the system is improved.

Based on the technical scheme, compared with the prior art, the photomultiplier performance testing device has at least one of the following beneficial effects:

1. the method has high automation degree, and can effectively save the measuring time and the labor cost. Aiming at the multi-parameter test requirement of PMT performance, the system realizes the automation of real-time control and data acquisition on a signal source, a light source, a high voltage and a VME data acquisition system. And after each parameter is tested, automatically calling data analysis software to perform data analysis on the test result, and outputting the analysis result to a database, wherein the data can be read and used by a subsequent measurement program. Finally, the measurement program of each parameter is placed in the sequential structure of LabVIEW, so that the measurement program can measure a plurality of parameters in a one-key sequence.

2. And a plurality of PMTs can be measured simultaneously, and batch test of PMT performance is realized. The reason why multiple PMTs can be measured simultaneously is that: the light source is led out by a plurality of paths of optical fibers through the light mixing and splitting device, the photocathodes of a plurality of PMTs can be illuminated at the same time, and the light intensity ratio is 0.9-1.1; the dark box can contain a plurality of PMTs; the electronic multiplex system is designed to have flexible and expandable functions.

3. The test parameters are comprehensive, and the dynamic range is large. Through the connection mode of the reasonable design hardware and the triggering and selection of different test modules through the BNC, the testing of multiple parameters of the PMT by one set of device is realized. Meanwhile, the system designs an inverter circuit and matched measurement electronics for PMT dynode signals, and effectively expands the dynamic range of measurement parameters.

4. The method has the function of quickly measuring the pulse distribution after PMT in a large time range. The new multi-hit time-to-digital converter TDC is adopted to record the over-threshold time of the rear pulse, so that the time range (up to 52 microseconds) of rear pulse measurement is expanded, the distribution of the rear pulse along with the arrival time can be obtained, and the measurement speed and the measurement precision are effectively improved.

Drawings

FIG. 1 is a control panel and data analysis panel of a prior art photomultiplier tube performance test platform;

FIG. 2 shows a PMT test set configuration according to an embodiment of the present invention;

FIG. 3 is a schematic view of a test chamber according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a light source system according to an embodiment of the present invention;

FIG. 5 is a block diagram of an electronic system of an embodiment of the present invention;

FIG. 6 is a circuit schematic diagram of a gate and an inverter according to an embodiment of the present invention, wherein FIG. 6(a) is the gate and FIG. 6(b) is the inverter;

FIG. 7 is a flow chart of PMT testing according to an embodiment of the present invention.

Detailed Description

The invention discloses a set of testing device capable of measuring the comprehensive performance parameters of photomultiplier tubes in batches with high automation. The main technical problem who solves includes:

1. automated control of the test apparatus and the test procedure. And the signal source, the light source, the high-voltage system and the VME data acquisition system which are required by the measurement of various performance parameters of the PMT are automatically controlled. After the data acquisition is finished, a special data analysis program written based on ROOT software (general software framework in the field of high-energy physical research) can be automatically called, the real-time analysis of the online data is realized, and parameters required by subsequent measurement are output to a text for the subsequent measurement program to read. After each parameter measurement and analysis is completed, the next measurement is automatically started, and finally, various parameters required by one-click sequential measurement are realized.

2. A special high-bandwidth inverter circuit is designed and manufactured for PMT dynode signals. The dynode signal after phase inversion can be directly measured by a charge digital converter (QDC), so that the system can measure the output signal of the dynode and related performance parameters while measuring the anode negative signal, and the dynamic range of system measurement is effectively expanded.

3. An experimental device and an experimental method for measuring the pulse after the PMT based on a multi-hit time-to-digital converter (multi-hit TDC) are developed, and the rapid measurement of the pulse time distribution after the PMT is realized.

Aiming at the requirement of measuring the comprehensive performance of the high-performance photomultiplier, the invention designs and manufactures a novel photomultiplier performance testing device, and realizes the highly-automated batch test of the comprehensive performance of the photomultiplier by developing matched hardware and software. The invention can be applied to the occasions needing to measure the comprehensive performance parameters of the photomultiplier rapidly and accurately in large batch, and can effectively save the measuring time and the labor cost. The method has wide application prospect for the research and development of high-performance photosensitive devices.

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

FIG. 2 shows a designed photomultiplier tube test setup configuration, including a dark box, a light source system, a high voltage system, electronics, and a data acquisition and control system.

1) Dark box with geomagnetic shielding function

The designed dark box is shown in fig. 3. The camera bellows provides a light-resistant and geomagnetic shielding environment for PMT test, the camera bellows is 1.9 × 1 × 1.2 meters in length, width and height, each camera bellows can hold 8 PMTs, and the test system comprises two camera bellows, can test 16 large-size PMTs at the same time. Each camera was equipped with a bracket for mounting and securing a test bucket, 0.8 meters long and 9 inches inside diameter. The PMT is placed in the test barrel through the support, the photocathode of the PMT faces the rear end of the test barrel, the rear end of the test barrel is in contact with the back surface of the dark box, the optical fiber is installed on the back surface of the dark box, and the pulse light beam generated by the light source system irradiates on the photocathode of the PMT through the optical fiber. The test bucket, PMT, and fiber were coaxial. The permalloy is wrapped outside the testing barrel, so that the intensity of the geomagnetic field can be attenuated to one tenth of the original intensity. The anode signal, dynode signal and high voltage of PMT are led out through BNC and SHV cable adapter in front of the black box. The two doors of the measuring box are all provided with protection switches, the two testing boxes are connected with the interlock of the high-voltage system in series through cables, the access of any one door is opened, the high-voltage system prohibits high-voltage output through the interlock function, and the PMT is prevented from being damaged due to strong exposure when high voltage is applied.

2) Light source system

The light source system comprises two LEDs (Hebei 510LB7C, 460 and 475nm), a picosecond laser (HamamatsuPLP-10, 405nm), a light mixing splitter and an outgoing optical fiber. The light source system design is shown in fig. 4. The light from the laser source was introduced by an optical fiber and the LED was driven by a signal generator (Tektronix AFG 3252). The light is then totally reflected multiple times in the cylindrical light pipe to form uniform light spots. An optical fiber bundle is tightly coupled to the output section of the light guide pipe, and 16 output optical fibers at the other end of the optical fiber bundle are mutually separated and connected to an optical fiber interface at the back of the camera bellows. The light intensity ratio of the output of each optical fiber is between 0.9 and 1.1.

3) Design scheme of electronic system

The electronics system is shown in fig. 5. The whole system is controlled by a signal generator BNC575(Berkeley Nucleonics Corp.), wherein the BNC575 is provided with 4 independent channels, and each channel can be independently switched on and off. Each channel is set to be synchronized with the signal generator internal clock T0, and the period of T0 and the delay time of each channel with respect to T0 are adjustable. Channel a inputs the fan-in fan-out (FIFO, CAEN N625), converts the TTL signal to the NIM signal, and then inputs the clock (CAEN, N93B), the output of which is the trigger signal for TDC (CAEN V1290A) and the gate signals for the three QDCs. The channel B external trigger signal source (TektronixAFG3252) and the Tektronix AFG3252 can provide two independent outputs to respectively drive the two LEDs to emit light, and the width, the amplitude and the frequency of a driving level are adjustable. The channel C is converted into an NIM signal by fan-in and fan-out, and then screened by the discriminator 2(CAENV814) to be used as the reference time (time accuracy about several nanoseconds) of the pulse test after PMT. And triggering a picosecond laser (Hamamatsu PLP-10) to emit light outside the channel D, and generating a path of synchronous output while the picosecond laser emits light to serve as reference time (the time precision is about tens of picoseconds) for PMT (photomultiplier tube) transition time dispersion measurement.

The input high voltage of PMT is provided by CAEN SY2527 system, and the SY2527 can install positive high voltage output module (such as CAENA1535SP) or negative high voltage output module (such as CAENA153DN) according to the requirement of PMT for high voltage.

The anode signal of PMT is input into a multi-way gating device, and each way of the gating device has an input and two outputs: the first output of the gate is connected to QDC2(CAEN V792N) for measuring the linear range of the anode output; the second output of the gate is input to a tenfold amplifier (CAEN N979) for measuring the performance of the PMT in relation to the single photon state. The tenfold amplifier has two identical outputs: one input QDC1(CAEN V965) for measuring single photoelectron spectrum, energy resolution and detection efficiency; the other path is input into a low threshold discriminator (CAEN V814). The low-threshold discriminator has two paths of identical outputs: one path is input into a TDC and used for measuring transit time dispersion and rear pulse; the other input to the scaler (CAEN V830) is used to measure the dark noise count. The dynode signal of the PMT is input to a multi-way inverter and then to QDC3(CAEN V965) for measuring the linear range of the dynode output. Together, QDC2 and QDC3 can be used to measure the gain ratio between the anode and dynode.

The circuit diagram of the gate and the inverter is shown in fig. 6, in which fig. 6(a) shows the gate and fig. 6(b) shows the inverter. The gating device realizes the gating of one of the two paths of outputs through a single-pole double-throw switch. The inverter is an active inverter implemented based on a commercial operational amplifier AD 8000.

4) Control and data acquisition system

The test system and the computer communicate through LabVIEW. The modules communicating with the computer are labeled in fig. 5 as shaded modules, including: low threshold discriminator (CAEN V814), scaler (CAEN V830), TDC (CAEN V1290A), QDC (CAEN V965 and V792N).

The signal generators BNC575 and Tektronix AFG3252 are connected to a test computer by an RS232 serial bus and a USB bus, the types of test parameters and the turning on or off of a certain light source are controlled by controlling switches of different channels of the BNC575, the light emitting frequency of the light source is controlled by controlling the frequency of internal clocks T0 and Tektronix AFG3252 of the BNC575, the light intensity of an LED is controlled by controlling the width and the amplitude of the driving level of the Tektronix AFG3252, and the relative delay of a PMT signal and a gate signal, a trigger signal and the like is controlled by controlling the relative delay of each channel of the BNC relative to the internal clock T0.

The high-voltage system is connected to a test computer through a network cable interface, and automatic control and real-time monitoring of high voltage are realized through a TCP/IP protocol and an OPC server.

The data acquisition system controls all functional plug-ins in the VME system through the VMEbus, including QDC, TDC, a discriminator, a scaler and the like. After the measurement data is acquired, a system exec.vi of LabVIEW is used for executing a computer system command to call ROOT software commonly used in the field of high-energy physical research to analyze the measurement data.

The measurement flow of the device is shown in fig. 7.

1) And (6) measuring the stability.

The gate gates a decade amplifier (CAEN N979). LabVIEW was used to set up as follows: opening only BNC575 channels A and BThe period of the BNC internal clock T0 is set to 0.00025 seconds, the delay of channel a to T0 is set to 0.00000061025 seconds, and the delay of channel B to T0 is set to 0.00000017575 seconds (to drop the PMT signal into the gate signal); opening Tektronix AFG3252 channel A, setting channel A output frequency to 4000 Hz, setting channel A output level width to 4 ns, and output level amplitude to 2.75V (making each PMT receive light intensity of about 30 photoelectrons); controlling the high voltage output of the high voltage system to make each PMT work at the factory recommended high voltage (or a certain fixed high voltage) HV₀(ii) a The threshold of the low-threshold discriminator 1 is set to 16 millivolts (1/3 photoelectrons).

The charge output of the PMT anode was first measured every 15 minutes, followed by the turn off of BNC channels a and B, the turn off of Tektronix AFG3252 channel a, and then the dark noise count rate was measured for 5 minutes. The entire stability test lasted 12 hours.

And after the counting is finished, automatically calling an analysis program through LabVIEW to obtain a change curve of the gain and the dark noise counting rate along with time, and calculating the change of the gain and the dark noise counting rate from 3 hours to 12 hours after the stability. After the analysis is finished, the measurement of the next parameter is automatically started.

2) Single photoelectron spectroscopy.

High voltage HV recommended at factory₀(or some fixed high pressure) for the first time. LabVIEW was used to set up as follows: opening only BNC575 channels A and B, setting the cycle of BNC internal clock T0 to 0.0005 seconds, delay of channel A to T0 to 0.00000061025 seconds, and delay of channel B to T0 to 0.00000017575 seconds (dropping PMT signal into gate signal); opening Tektronix AFG3252 channel A, setting channel A output frequency to 4000 Hz, setting channel A output level width to 4 ns, and output level amplitude to 2.35V (making each PMT receive light intensity of about 0.1 photoelectron); controlling the high voltage output of the high voltage system to make each PMT work at the factory recommended high voltage (or a certain fixed high voltage) HV₀。

The single photoelectron spectrum was measured using QDC 1. After the counting is finished, an analysis program is automatically called through LabVIEW to obtain the PMT in HV₀Absolute increase ofIt is beneficial to. After the analysis is finished, the measurement of the next parameter is automatically started.

3) High voltage gain curve measurements.

LabVIEW was used to set up as follows: opening only the BNC575 channels A and B, setting the cycle of the BNC internal clock T0 to 0.00025 seconds, the delay of channel A relative to T0 to 0.00000061025 seconds, and the delay of channel B relative to T0 to 0.00000017575 seconds (dropping the PMT signal into the gate signal); the Tektronix AFG3252 channel a was turned on, setting the channel a output frequency to 4000 hz, the channel a output level width to 4 ns, and the output level amplitude to 2.75 v (with each PMT receiving an intensity of about 30 photoelectrons).

Using QDC1, at HV in 50 volt steps₀Measuring the charge output by the PMT anode in the range of +/-150V to obtain the variation relation of the output charge of the PMT along with high voltage, and combining the PMT obtained in the measurement 2) in HV₀And obtaining the variation relation of the PMT gain along with the high voltage. Calculate each PMT at 2 x 10⁶The high voltage required at gain (working gain) (working high voltage) is output to the text workhv. After the analysis is finished, the measurement of the next parameter is automatically started.

4) Single photoelectron spectrum, peak-to-valley ratio, relative quantum efficiency, and dispersion over time under working gain.

LabVIEW was used to set up as follows: turn on only BNC575 channels a and D (turn off LED, turn on picosecond laser), set the period of BNC internal clock T0 to 0.00025 seconds, delay of channel a to T0 to 0.00000059025 seconds, delay of channel D to T0 to 0.00000017575 seconds (drop PMT signal into gate signal); pre-adjusting the size of the picosecond laser grating (so that each PMT receives light intensity of about 0.3 photoelectrons); setting the threshold of the low-threshold discriminator 1 to 12 millivolts (1/4 photoelectrons); and reading a file work HV.txt for recording the working high voltage, controlling the high voltage output of the high voltage system, enabling each PMT to work at the working high voltage, and waiting for 5 minutes.

The single photoelectron spectrum was measured by QDC1 while the time-of-flight dispersion was measured by TDC. The peak-to-valley ratio and the energy resolution can be obtained by analyzing the single photoelectron spectrum, and the relative quantum efficiency of the PMT to be measured is obtained by combining the light intensity of each optical fiber obtained by the scale of the reference tube with known quantum efficiency in advance. After the analysis is finished, the measurement of the next parameter is automatically started.

5) And measuring dark noise.

LabVIEW was used to set up as follows: closing all channels of the BNC 575; controlling the high-voltage output of the high-voltage system to enable each PMT to work at a working high voltage; setting the threshold of the low-threshold discriminator 1 to 16 millivolts (1/3 photoelectrons); wait for 5 minutes.

The dark noise count rate is measured using a scaler. After the analysis is finished, the measurement of the next parameter is automatically started.

6) Post pulse rate measurement.

LabVIEW was used to set up as follows: opening only the BNC575 channels A and B, setting the cycle of the BNC internal clock T0 to 0.00025 seconds, the delay of channel A relative to T0 to 0.00000061025 seconds, and the delay of channel B relative to T0 to 0.00000017575 seconds (dropping the PMT signal into the gate signal); opening Tektronix AFG3252 channel A, setting channel A output frequency to 4000 Hz, setting channel A output level width to 4 ns, and output level amplitude to 2.75V (making each PMT receive light intensity of about 30 photoelectrons); controlling the high-voltage output of the high-voltage system to enable each PMT to work at a working high voltage; the threshold of the low-threshold discriminator 1 is set to 16 millivolts (1/3 photoelectrons).

The number of photoelectrons corresponding to the PMT main pulse is first measured using QDC 1.

After the measurement of the number of the main pulse photons is finished, the LabVIEW is used for setting as follows: additionally opening a BNC575 channel C, setting the period of a BNC internal clock T0 to be 0.0005 seconds, and setting the delay of the channel C relative to T0 to be 0.000000470 seconds; the threshold of low-threshold discriminator 1 is set to 12 millivolts (1/4 photoelectrons) and the threshold of low-threshold discriminator 2 is set to 400 millivolts.

The post-pulse over-threshold time is recorded using TDC and ultimately converted to post-pulse rate.

The test procedure is automatically completed in sequence from steps 1) to 6), which, until now, required the manual gating of the gate to QDC2, and then the measurement step 7) is started.

7) Anode dynode non-linear measurements and anode dynode gain ratio.

After gating the gate QDC2 manually, LabVIEW was used to set up as follows: opening only the BNC575 channels A and B, setting the cycle of the BNC internal clock T0 to 0.00025 seconds, the delay of channel A relative to T0 to 0.00000061025 seconds, and the delay of channel B relative to T0 to 0.00000017575 seconds (dropping the PMT signal into the gate signal); setting the output frequencies of channels A and B of Tektronix AFG3252 to be 4000 Hz, setting the output level widths of the channels A and B to be 4 ns, and setting the delays of the channels A and B to be 0 ns; the high voltage output of the high voltage system is controlled so that each PMT operates at an operating high voltage.

The Tektronix AFG3252 channels A and B were made to drive the LED A and B lamps, respectively, and the intensity of the LEDs was varied by varying the magnitude of the Tektronix FG3252 output level. The charge output from the PMT anode was measured using QDC2 and the charge output from the dynode was measured using QDC 3. The AB method was used to measure the nonlinear curves of the anode and dynode, while the anode dynode gain ratio could be measured.

The performance of the PMT was tested to completion, and the measurement time from the start of the measurement to the stop of the cycle was 15 hours (including the 12-hour stability measurement), and the measurement accuracy of each parameter of the apparatus is shown in table 1.

Table 1 measurement accuracy of various parameters of the apparatus.

Parameter(s)	Measurement accuracy
		Operating high pressure (%)	0.8
Peak-to-valley ratio of single photoelectron spectrum	0.2
		Time of flight dispersion (nanosecond)	0.2
Relative quantum efficiency (%)	5
		Dark noise count rate (Hertz)	＜500
Rear pulse Rate (%)^*	0.2
		Anode dynode gain ratio (%)	1
Anode nonlinearity (%)^*	0.4
		Dynode nonlinearity (%)^*	0.4

Note: the measured parameter indicates the parameter itself in percent.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A photomultiplier performance test device is characterized by comprising a dark box, a light source system, a high-voltage system, an electronics system and a data acquisition and control system; wherein the content of the first and second substances,

2. The photomultiplier tube performance test apparatus of claim 1 wherein the optical fiber, high voltage cable and signal cable in the dark box are connected to an external instrument through the dark box.

3. The photomultiplier tube performance test apparatus of claim 1, wherein the door of the camera shelter automatically shuts off the high voltage power supply when opened.

4. The photomultiplier tube performance test apparatus according to claim 1, wherein the light source system includes an LED, a picosecond laser, a light mixing splitter, and an extraction fiber; the light generated by the LED and the picosecond laser is LED out by a plurality of optical fibers through the light mixing and splitting device, the optical fibers penetrate through the dark box, the size of each optical fiber spot is adjustable, and all photocathodes of a single photomultiplier can be covered.

5. The apparatus for testing photomultiplier tube performance according to claim 4, wherein the light generated by the LED and the picosecond laser is totally reflected in the cylindrical light pipe multiple times, a fiber bundle is tightly coupled to the output section of the light pipe, the other end of the fiber bundle is connected to the fiber interface on the back of the black box with 16 output fibers separated from each other, and the ratio of the relative change of the light intensity output by each fiber is 0.9-1.1.

6. The photomultiplier tube performance test apparatus according to claim 1, wherein the electronic system includes a multi-channel signal generator, a gate, an inverter and an amplifier, the signal generator is configured to provide a plurality of outputs, each output is independently switchable, each output is configured to be synchronized with a generator internal clock T0, a frequency of T0 and a delay time of each output with respect to T0 are adjustable, and wherein the first output is configured to provide a gate signal and a trigger signal for the electronic system; the second output external trigger signal source can provide two independent outputs to respectively drive the two LEDs to emit light, and the width and amplitude of the drive signal are adjustable; the third path of output triggers the picosecond laser to emit light, and a synchronous output signal generated when the picosecond laser emits light is used as reference time for measuring the dispersion of the transit time of the photomultiplier; the fourth output can provide a reference time for the post-pulse measurement.

7. The photomultiplier tube performance test apparatus of claim 1 wherein the data acquisition and control system includes a low threshold discriminator, a scaler, a time to digital converter, a charge to digital converter.

8. The apparatus of claim 6, wherein each of the gates has an input and two outputs, wherein one of the outputs is connected to the second charge-to-digital converter for measuring linearity of the anode output; the other path of output is connected with a tenfold amplifier for measuring the performance related to the single photon state of the photomultiplier; outputting signals amplified by a tenfold amplifier in a fan-out way, and outputting the signals in a first charge digital converter in a second way, wherein the first charge digital converter is used for measuring a single photoelectron spectrum, energy resolution and detection efficiency; the other path of signal is input into a low-threshold discriminator, and the low-threshold discriminator outputs two paths of discriminating signals: one path of signal is input into a time-to-digital converter and is used for measuring the transit time dispersion and the rear pulse; the other path of signal is input into a scaler for measuring dark noise count; inputting a dynode signal of the photomultiplier into an inverter, and then inputting the dynode signal into a third charge digital converter for measuring the linear range output by the dynode; the second charge-to-digital converter and the third charge-to-digital converter in combination can be used to measure the gain ratio between the anode and the dynode.

9. A testing method using the photomultiplier tube performance testing apparatus according to any one of claims 1 to 8, comprising the steps of:

carrying out test setting according to the type of the measurement parameter;

reading measurement data recorded by an electronic system;

analysis software is invoked to analyze the measurement data.

10. The test method of claim 9, wherein the measurement parameters include stability, single photoelectron spectrum, high voltage gain curve, single photoelectron spectrum at operating gain, peak-to-valley ratio, relative quantum efficiency, time-of-flight dispersion, dark noise, and post-pulse;