An Adaptive Voltage Regulation Method for a Photon Counting Device

Abstract

The present invention discloses an adaptive voltage regulation method for a photon counting device. 1. Turn on an external reference light source to irradiate the light incident window of a photomultiplier tube. 2. When the photon counting device is powered on initially, a single-chip microcomputer controls an internal preheating light source to preheat the photomultiplier tube. 3. The host computer adjusts the analog voltage signal of the single-chip microcomputer according to the communication protocol, controls the AC voltage output by the high-frequency inverter unit to increase gradually from small to large within a set range, and at the same time, the single-chip microcomputer sequentially outputs the count values to the host computer through the communication interface. The host computer describes the plateau voltage curve based on the sequentially output voltage values and the measured count values, and issues parameters to the single-chip microcomputer to set the plateau voltage according to the trend of the plateau voltage curve, thereby completing the adaptive adjustment of the plateau voltage and discrimination level of the photon counting device. The present invention realizes the adaptive adjustment control of the plateau voltage and discrimination level of the photomultiplier tube according to the individual differences of the photomultiplier tubes, without the need to open the light-tight enclosure of the counting device for manual adjustment.

Description

Technical Field

[0001] The present invention relates to the field of photon counting, and in particular to an adaptive voltage regulation method for a photon counting device. Background Art

[0002] Due to the individual differences of photomultiplier tubes, for each photon counter matched with a photomultiplier tube, different plateau voltages and discrimination level parameters need to be matched; the plateau voltage refers to the voltage between the anode and the cathode when the photomultiplier tube operates relatively stably and the amplification factor meets the requirements. Therefore, after the photon counter is assembled, it is necessary to adjust the plateau voltage and discrimination level of the photon counter to match the photomultiplier tube of the photon counter. Currently, the adjustment of the plateau voltage and discrimination voltage is mostly completed by manually adjusting resistors or potentiometers. Manual adjustment requires opening the outer shell of the photon counter and directly operating on the circuit board, and the photomultiplier tube is in the powered-on state during adjustment. Since the photomultiplier tube has a very high light sensitivity and has high requirements for the dark environment, if light leakage (with an intensity equivalent to moonlight) occurs, it can cause an increase in the dark count of the photomultiplier tube and it cannot return to the normal value in a short time. In severe cases, it can cause permanent damage to the photomultiplier tube. In addition, there is a high voltage of more than 1000V inside the photon counter, and there are great safety risks in manually opening the outer shell for adjustment operations. At the same time, when the existing photon counter is powered on again after not being powered on for a long time, it is necessary to power on the photomultiplier tube in a dark environment for 1 - 2 hours for preheating, which also reduces the working efficiency of the photon counter. Summary of the Invention

[0003] The purpose of the present invention is to provide an adaptive voltage regulation method for a photon counting device, which realizes non-contact adjustment of photomultiplier tube parameters, improves the flexibility and safety of parameter adjustment, and reduces the harsh requirements for the adjustment environment.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] The adaptive voltage regulation method for the photon counting device of the present invention adopts the following photon counting device:

[0006] The photon counting device includes a light-shielding and airtight outer shell. A power input interface, a communication interface, and a light incident window of the photomultiplier tube are arranged on the wall of the light-shielding and airtight outer shell. Inside the light-shielding and airtight outer shell, there are:

[0007] A high-frequency inverter unit for inverting the low-voltage DC voltage input from the power input interface into a high-voltage AC voltage;

[0008] A voltage multiplier rectification unit for generating a multi-stage high-voltage DC voltage by multi-stage voltage multiplier rectification of the high-voltage AC voltage output by the high-frequency inverter unit to provide a corresponding DC voltage for the dynodes of the photomultiplier tube;

[0009] A signal amplification unit, configured to output amplified first and second differential signals after AC coupling of the signals between the anode and the last dynode of a photomultiplier tube; the first differential signal is superimposed on the first analog voltage signal output by a single-chip microcomputer and then connected to the first input terminal of a discrimination and comparison unit, and the second differential signal is connected to the second input terminal of the discrimination and comparison unit;

[0010] A discrimination and comparison unit, configured to compare the signals input to the first and second input terminals and then output to a pulse shaping unit;

[0011] The pulse shaping unit is configured to perform amplitude and edge shaping on the valid signals discriminated by the discrimination and comparison unit for recognition by a counting unit;

[0012] The counting unit is configured to count the pulses output by the pulse shaping unit and output the count value to the single-chip microcomputer;

[0013] The single-chip microcomputer reads the photon count value through a preset protocol, receives the instructions sent by the host computer through the communication interface, and adjusts the threshold values of the plateau voltage and the discrimination level of the photomultiplier tube; and at the initial power-on of the photon counting device, controls the built-in preheating light source to preheat the photomultiplier tube according to a set time;

[0014] The adaptive voltage regulation method is as follows:

[0015] Step 1: Turn on an external reference light source to irradiate the light incident window of the photomultiplier tube;

[0016] Step 2: At the initial power-on of the photon counting device, the single-chip microcomputer controls the built-in preheating light source to preheat the photomultiplier tube according to a set time;

[0017] Step 3: After the preheating of the photomultiplier tube is completed, the host computer adjusts the second analog voltage signal of the single-chip microcomputer through the communication interface according to the communication protocol, controls the AC voltage output by the high-frequency inverter unit to increase sequentially from small to large within a set range, and at the same time the single-chip microcomputer sequentially outputs the count value to the host computer through the communication interface; the host computer describes the plateau voltage curve according to the sequentially output voltage values and the measured count values, and issues parameters to the single-chip microcomputer to set the plateau voltage according to the trend of the plateau voltage curve;

[0018] Step 4: The host computer adjusts the first analog voltage signal of the single-chip microcomputer through the communication interface according to the communication protocol, controls the discrimination level of the discrimination and comparison unit to increase sequentially from small to large, and at the same time the single-chip microcomputer sequentially outputs the count value to the host computer through the communication interface. The host computer calculates the threshold range according to the set discrimination threshold and the measured count values, and issues it to the single-chip microcomputer to set the discrimination threshold, thereby completing the adaptive adjustment of the plateau voltage and the discrimination level of the photon counting device.

[0019] Optionally, the preheating light source is an LED light source. Each time power is re - applied initially, the single - chip microcomputer turns on the LED light source for 1 - 2 minutes to preheat the photomultiplier tube and then turns it off.

[0020] Optionally, the discrimination and comparison unit is a comparison amplifier.

[0021] Optionally, the signal amplification unit is a differential amplifier.

[0022] The advantages of the present invention are reflected in the following aspects:

[0023] 1. According to the individual differences of photomultiplier tubes, it realizes the adaptive adjustment and control of the plateau voltage and discrimination level of the photomultiplier tube. There is no need to open the light - proof and air - tight shell of the counting device for manual adjustment, which reduces the harsh requirements for the environment during the adjustment process and also eliminates the safety risks existing in the adjustment operation.

[0024] 2. When the photon counting device is powered on for the first time after a long period of non - use, the photomultiplier tube can be preheated for 1 - 2 minutes through the preheating light source arranged in the light - proof and air - tight shell, which greatly shortens the preheating time of the photomultiplier tube.

[0025] 3. By leading out two - way signals from the anode and the last - stage dynode of the photomultiplier tube, it realizes the filtering of common - mode interference signals.

[0026] 4. High integration level; the driving, signal processing, and signal output of the photomultiplier tube communicate with the host computer through the bus, with strong anti - interference ability, and realize adaptive detection and calibration.

[0027] 5. Low cost; there are no high - end programmable devices such as FPGA and CPLD, and all hardware circuits are implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the circuit structure block diagram of the photon counting device of the present invention.

[0029] Figure 2 is the layout schematic diagram of the single - chip microcomputer, preheating light source, and photomultiplier tube in the light - proof and air - tight shell of the present invention.

[0030] Figure 3 is the flow block diagram of the adaptive voltage regulation method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will describe the embodiments of the present invention in detail with reference to the drawings. These embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific working processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0032] The adaptive voltage regulation method of the photon counting device described in the present invention adopts the following photon counting device:

[0033] As Figures 1-3 shown, the photon counting device includes a light-shielding and airtight housing 1. A power input interface 2, a communication interface 3, and a light incident window 4 of a photomultiplier tube are hermetically arranged on the side wall of the light-shielding and airtight housing 1. The following components are arranged inside the light-shielding and airtight housing 1:

[0034] A high-frequency inverter unit for inverting the low-voltage DC voltage input from the power input interface 2 into a high-voltage AC voltage;

[0035] A voltage multiplier rectification unit for generating a multi-stage high-voltage DC voltage by multi-stage voltage multiplier rectification of the high-voltage AC voltage output by the high-frequency inverter unit to provide a corresponding DC voltage for the dynodes of the photomultiplier tube;

[0036] A signal amplification unit for amplifying and outputting the signal between the anode and the last dynode of the photomultiplier tube after AC coupling; Advantageously or exemplarily, the signal amplification unit has a differential amplifier. The first differential signal of the differential amplifier is superimposed on the first analog voltage signal V1 output by the single-chip microcomputer and then connected to the first input end of the discrimination and comparison unit, and the second differential signal is connected to the second input end of the discrimination and comparison unit;

[0037] A discrimination and comparison unit for comparing the signals input to its first and second input ends and then outputting to the pulse shaping unit;

[0038] Advantageously or exemplarily, the discrimination and comparison unit selects a comparison amplifier; the comparison amplifier compares the signals input to the first and second input ends, discriminates the valid signal and outputs it, that is: when the amplitude difference between the two amplified signals is greater than the set value, it is regarded as a valid signal, and if the amplitude difference is less than the set value, it is regarded as an invalid signal.

[0039] A pulse shaping unit for amplitude and edge shaping of the valid signal output by the discrimination and comparison unit and then outputting it to the counting unit for the counting unit to identify;

[0040] A counting unit for counting the number of pulses output by the pulse shaping unit and outputting the count value to the single-chip microcomputer;

[0041] A single-chip microcomputer reads the photon pulse count value through a preset protocol, receives the instruction sent by the upper computer through the communication interface, and adjusts the plateau voltage of the photomultiplier tube and the threshold of the discrimination level; and at the initial power-on of the photon counting device, controls the built-in preheating light source to preheat the photomultiplier tube;

[0042] The adaptive voltage regulation method is as follows:

[0043] Step 1: The host computer issues an instruction to control the opening of the light incident window 4 of the external reference light source to irradiate the photomultiplier tube, so as to meet the condition that the photomultiplier tube can multiply photons and output a certain number of pulses only when there is light.

[0044] Step 2: When the photon counting device is powered on initially, the single-chip microcomputer controls the built-in preheating light source 5 to preheat the photomultiplier tube for 1 - 2 minutes according to the set time; Step 3: After the preheating of the photomultiplier tube is completed, the host computer adjusts the second analog voltage signal V2 of the single-chip microcomputer according to the communication protocol through the communication interface, controls the AC voltage output by the high-frequency inverter unit to increase gradually from small to large within the set range, and at the same time the single-chip microcomputer sequentially outputs the corresponding count values to the host computer through the communication interface; The host computer describes the plateau voltage curve based on the sequentially output voltage values and the corresponding count values, and issues parameters to the single-chip microcomputer according to the trend of the plateau voltage curve to set the plateau voltage matching the photomultiplier tube; that is: the plateau voltage curve is the relationship curve between the voltage value and the count value, and according to the plateau voltage curve, the point where the count value is close to the reference light source value and the trend is relatively flat is found.

[0045] Step 4: The host computer adjusts the first analog voltage signal V1 of the single-chip microcomputer according to the communication protocol through the communication interface, controls the discrimination level of the discrimination comparison unit to increase gradually from small to large, and at the same time the single-chip microcomputer sequentially outputs the corresponding count values to the host computer through the communication interface. The host computer calculates the discrimination threshold interval according to the set discrimination threshold and the corresponding count values and issues it to the single-chip microcomputer to set the discrimination level threshold matching the photomultiplier tube, thereby completing the adaptive adjustment of the plateau voltage and the discrimination level of the photon counting device.

Claims

1. An adaptive voltage regulation method for a photon counting device, characterized in that: the following photon counting device is adopted: the photon counting device includes a light-shielding and airtight housing, on the wall of the light-shielding and airtight housing, there are a power input interface, a communication interface and a light incident window of a photomultiplier tube, and inside the light-shielding and airtight housing, there are provided: a high-frequency inverter unit for inverting the low-voltage DC voltage input by the power input interface into a high-voltage AC voltage; a voltage multiplier rectification unit for generating multiple levels of high-voltage DC voltage by multi-stage voltage multiplier rectification of the high-voltage AC voltage output by the high-frequency inverter unit to provide corresponding DC voltages for the dynodes of the photomultiplier tube; a signal amplification unit for outputting amplified first and second differential signals after AC coupling of the signals between the anode and the last-stage dynode of the photomultiplier tube; the first differential signal is connected to the first input end of the discrimination and comparison unit after being superimposed with the first analog voltage signal output by the single-chip microcomputer, and the second differential signal is connected to the second input end of the discrimination and comparison unit; a discrimination and comparison unit for comparing the signals input by the first and second input ends and outputting them to the pulse shaping unit; the pulse shaping unit for performing amplitude and edge shaping on the valid signals discriminated by the discrimination and comparison unit for the counting unit to identify; the counting unit for counting the pulses output by the pulse shaping unit and outputting the count value to the single-chip microcomputer; the single-chip microcomputer reads the photon count value through a preset protocol, receives the instructions sent by the upper computer through the communication interface, and adjusts the plateau voltage of the photomultiplier tube and the threshold value of the discrimination level; and at the initial power-on of the photon counting device, controls the built-in preheating light source to preheat the photomultiplier tube according to the set time; the adaptive voltage regulation method is: Step 1, turn on the external reference light source to irradiate the light incident window of the photomultiplier tube; Step 2, at the initial power-on of the photon counting device, the single-chip microcomputer controls the built-in preheating light source to preheat the photomultiplier tube according to the set time; Step 3, after the preheating of the photomultiplier tube is completed, the upper computer adjusts the second analog voltage signal of the single-chip microcomputer through the communication interface according to the communication protocol, controls the AC voltage output by the high-frequency inverter unit to increase gradually from small to large within the set range, and at the same time the single-chip microcomputer sequentially outputs the count value to the upper computer through the communication interface; the upper computer describes the plateau voltage curve according to the sequentially output AC voltage and the measured count value, and issues parameters to the single-chip microcomputer to set the plateau voltage according to the trend of the plateau voltage curve; Step 4, the upper computer adjusts the first analog voltage signal of the single-chip microcomputer through the communication interface according to the communication protocol, controls the discrimination level of the discrimination and comparison unit to increase gradually from small to large, and at the same time the single-chip microcomputer sequentially outputs the count value to the upper computer through the communication interface, and the upper computer calculates the threshold range according to the set discrimination threshold and the measured count value, and issues it to the single-chip microcomputer to set the discrimination threshold, thereby completing the adaptive adjustment of the plateau voltage and the discrimination level of the photon counting device.

2. The adaptive voltage regulation method according to claim 1, characterized in that: The preheating light source is an LED light source. At the initial power-on, the single-chip microcomputer preheats the photomultiplier tube for 1 - 2 minutes.

3. The adaptive voltage regulation method according to claim 1 or 2, characterized in that: the discrimination and comparison unit is a comparison amplifier.

4. The adaptive voltage regulation method according to claim 1 or 2, characterized in that: the signal amplification unit is a differential amplifier.

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