A control circuit and a gated control method of an anode-grounded photomultiplier tube

Abstract

The present application relates to a kind of anode ground photomultiplier control circuit and gated control method, photomultiplier includes photoelectric cathode, first multiplication stage, second multiplication stage and third multiplication stage, control circuit also includes square wave drive signal input port, isolation transformer, rectifier circuit and gate control circuit connected in turn;Isolation transformer primary side is connected with drive signal input port, the intermediate tap of secondary side is connected with the photoelectric cathode, and secondary side is connected with rectifier circuit;Isolation transformer is used to when receiving square wave drive signal, the current output is powered for gate control circuit;When there is current input gate control circuit, the electric connection is turned on, and the potential difference of the first, second, third multiplication stage and photoelectric cathode is 0 to reduce PMT gain.The present application triggers time gate control circuit simultaneously by using square wave drive signal and powers time gate control circuit.When gate drive signal is provided in circuit input end, time gate control circuit is powered on, and PMT gain is reduced.

Description

Technical Field

[0001] This invention relates to the field of gating circuits for photomultiplier tubes, and more particularly to a control circuit and gating control method for an anode-grounded photomultiplier tube. Background Technology

[0002] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art.

[0003] Photomultiplier tubes (PMTs) are the detector of choice for high-performance photoluminescence spectrometers because of their excellent photosensitivity and ability to perform steady-state and time-resolved measurements. A PMT is a vacuum tube containing a photocathode, a series of electron multipliers called dynodes, and an anode; electrons are propelled from the cathode to the anode by applying a high voltage (HV).

[0004] When a photon strikes the photocathode, a photoelectron is emitted into the vacuum, accelerated by an applied voltage, and reaches the first dynode, where it generates secondary electrons for amplification. This electron multiplication process is repeated at each subsequent dynode, and the multiplied secondary electrons are collected at the anode (e.g., ...). Figure 1 The electron multiplication gain exceeds 1x10⁻⁶. 7 It is easy to achieve, which means that a single photon can generate a large current pulse, making it easy to detect and enabling highly sensitive photoluminescence detection.

[0005] A drawback of high electron multiplication gain is that the photoluminescence matrix (PMT) must be exposed to low light levels; otherwise, excessive current will be generated, saturating the PMT. In time-resolved photoluminescence measurements, the number of photons incident on the PMT during or immediately after a laser or flash pulse can easily saturate it. This leads to distortion in the measured photoluminescence decay and may cause irreversible damage to the PMT.

[0006] To overcome this problem, the PMT must be protected during periods of excessive light. One approach is to use a mechanical shutter to physically block light from entering the PMT, but this method has the drawback of slow shutter speeds and limited lifespan. A better approach is to electronically time-gated the PMT to reduce its electron multiplication gain during periods of excessive light intensity and to prevent excessive current generation.

[0007] PMT time gating is achieved by switching the voltages of the first N (typically 2-3) dynodes from their normal voltages to the same potential as the photocathode. When the first N dynodes are set to the same potential as the photocathode, the electron multiplication gain of the PMT is significantly reduced.

[0008] In a PMT (Power Mediator), a high voltage is applied across the anode and photocathode, and a voltage divider separates this voltage gradient across the photocathode, dynode, and anode. There are two ways to apply this high voltage: anode grounded and cathode grounded. In anode grounded mode, the anode is grounded and a negative high voltage is applied to the photocathode, while in cathode grounded mode, the photocathode is grounded and a positive high voltage is applied to the anode.

[0009] A cathode-grounded PMT is very simple, but its drawback is that it cannot be used for single-photon counting PMTs. Single-photon counting PMTs must use an anode-grounded method.

[0010] In a grounded PMT, the photocathode is at a voltage >1kV relative to ground, therefore the gating circuit design needs to be able to isolate the high-voltage switch. The gating circuit requires an additional low-voltage power supply (typically 4V-6V) to implement this switch. Summary of the Invention

[0011] Technical issues

[0012] In view of this, the technical problem to be solved by the present invention is to provide a control circuit and gate control method for an anode-grounded photomultiplier tube.

[0013] The control circuit of this invention does not require an additional low-voltage isolation power supply. It can simultaneously trigger and power the gate circuit through a square wave drive signal, which makes the PMT housing easier to integrate with a photoluminescence spectrometer, and lowers the cost.

[0014] Solution

[0015] To solve the above technical problems, embodiments of the present invention provide a control circuit for an anode-grounded photomultiplier tube. The photomultiplier tube includes a photocathode, and a first multiplier stage, a second multiplier stage, and a third multiplier stage connected together. The first multiplier stage is connected to the photocathode. The control circuit also includes a square wave drive signal input port, an isolation transformer, a rectifier circuit, and a gate circuit connected in sequence.

[0016] The drive signal input port is used to input a square wave drive signal;

[0017] The primary side of the isolation transformer is connected to the drive signal input port, the middle tap of the secondary side of the isolation transformer is connected to the photocathode, and the secondary side of the isolation transformer is connected to the rectifier circuit to supply power to the gate control circuit when a square wave drive signal is received.

[0018] The gating circuit is connected to the photocathode and the third multiplier stage respectively. The gating circuit is used to trigger the connection between the third multiplier stage and the photocathode to be turned on or off based on whether there is a current input: when there is a current input to the gating circuit, the connection is turned on so that the potential difference between the first, second and third multiplier stages and the photocathode is 0 to reduce the PMT gain; otherwise, the connection is turned off so that the PMT gain is at the normal level.

[0019] Furthermore, it also includes a signal generation circuit for connecting to the square wave drive signal input port, the signal generation circuit being used to generate a square wave drive signal according to a preset timing or on a timed basis;

[0020] Furthermore, the signal generation circuit includes a field-programmable gate array and an operational amplifier circuit;

[0021] The field-programmable gate array is used to generate two square wave logic signals with a specific duration and delay according to a preset value, and the two square wave logic signals are inverse signals of each other.

[0022] The operational amplifier circuit is used to output the two square wave logic signals as square wave drive signals.

[0023] Further, the operational amplifier circuit includes a first operational amplifier and a second operational amplifier connected together; optionally, the output terminal of the first operational amplifier is connected to a first resistor in parallel with the second operational amplifier; optionally, the input terminal and the output terminal of the second operational amplifier are respectively connected in series with a second and a third resistor; the second and third resistors are also connected in parallel with the first resistor; optionally, the first operational amplifier is also connected in parallel with a fourth resistor.

[0024] The first operational amplifier is used to output a square wave signal after two square wave logic signal inputs;

[0025] The second operational amplifier is used to input and output a square wave drive signal after the square wave signal.

[0026] Furthermore, the rectifier circuit includes a first rectifier circuit and a second rectifier circuit;

[0027] The gated circuit includes a Schmitt trigger, an inverter, and a switching circuit connected in sequence.

[0028] The positive and negative power supply pins of the Schmitt trigger are connected to the first rectifier circuit and the photocathode, respectively.

[0029] The input and output pins of the Schmitt trigger are connected to the output terminal of the second rectifier circuit and the input terminal of the inverter, respectively. The switching circuit is used to connect the third multiplier stage to the photocathode when the input pin of the Schmitt trigger is at a logic high potential, so that the first, second, and third multiplier stages are at the same potential as the photocathode.

[0030] Furthermore, it also includes a voltage regulator circuit connected between the output terminal of the first rectifier circuit and the photocathode, and a filter circuit connected between the output terminal of the second rectifier circuit and the photocathode.

[0031] Optionally, the voltage regulator circuit includes a resistor and a reverse diode connected in parallel; optionally, the voltage regulator circuit ensures that the circuit voltage does not exceed 6V; optionally, a filter capacitor is also connected in parallel with the voltage regulator circuit, and optionally, the energy stored in the filter capacitor can maintain power supply for ~50μs.

[0032] Optionally, the filter circuit includes a tenth resistor and a fourth capacitor connected in parallel; optionally, a seventh resistor is also connected between the second rectifier circuit and the input pin of the Schmitt trigger.

[0033] Furthermore, both the first and second rectifier circuits are half-bridge rectifier circuits. Optionally, the half-bridge rectifier circuit includes two rectifier diodes, and the anodes of the two rectifier diodes are respectively connected to the secondary side of the isolation transformer.

[0034] The switching circuit includes a field-effect transistor;

[0035] The output terminal of the inverter is electrically connected to the photocathode and the gate g terminal of the field-effect transistor, respectively; the source s terminal and the drain d terminal of the field-effect transistor are connected to the photocathode and the third multiplication stage, respectively; this is used to trigger the field-effect transistor to conduct the photocathode and the third multiplication stage when a logic high potential is input to the input pin of the Schmitt trigger, so that the first, second, and third multiplication stages are at the same potential as the photocathode.

[0036] Furthermore, a protective resistor is connected in series between the output terminal of the inverter and the gate g terminal of the field-effect transistor, and between the output terminal of the inverter and the photocathode; a protective resistor is connected in series between the source s terminal of the field-effect transistor and the photocathode.

[0037] Furthermore, both the Schmitt trigger and the inverter are NOT gates; optionally, the Schmitt trigger is a hex-inverting Schmitt trigger.

[0038] On the other hand, a gating control method for an anode-grounded photomultiplier tube is also provided, including: inputting a square wave drive signal to the isolation transformer at regular intervals or on a timed basis to power the gating circuit; when the gating circuit is powered, it connects the photocathode and the third multiplier stage, so that the potential difference between the photocathode and the second and third multiplier stages is 0, thereby reducing the PMT gain; when there is no square wave drive signal input to the isolation transformer, the gating circuit is disconnected to allow the PMT gain to return to normal.

[0039] Furthermore, the square wave drive signal is generated by the signal generation circuit according to a preset timing or on a fixed schedule;

[0040] Optionally, the signal generation circuit includes a field-programmable gate array (FPGA); optionally, the FPGA generates two 0 to +3.3V 50kHz square wave logic signals with a specific duration and delay according to a preset value, and the two square wave logic signals are inverse signals of each other;

[0041] Furthermore, the gate control method is controlled by the aforementioned control circuit.

[0042] Furthermore, the gate circuit includes a Schmitt trigger, an inverter, and a field-effect transistor connected in sequence; the Schmitt trigger and the inverter cooperate to trigger the field-effect transistor to conduct the photocathode and the third multiplier stage when a logic high potential is input to the input pin of the Schmitt trigger, so that the first, second, and third multiplier stages are at the same potential as the photocathode;

[0043] Furthermore, both the Schmitt trigger and the inverter are NOT gates; optionally, the Schmitt trigger is a hex-inverting Schmitt trigger.

[0044] Furthermore, the square wave drive signal is input to the primary side of the isolation transformer, the middle tap of the secondary side of the isolation transformer is connected to the photocathode, and the secondary side of the isolation transformer supplies power to the gate control circuit after rectification and smoothing.

[0045] Beneficial effects

[0046] (1) This invention uses a square wave drive signal (~50kHz~10V pk-pk AC square wave signal (gate drive signal)) to simultaneously trigger and power the time-gated circuit. When the gate drive signal is provided at the circuit input, the time-gated circuit is powered on, and the PMT gain decreases (PMT OFF). When no 50kHz gate drive signal is provided to the time circuit input, the time-gated circuit is unpowered, and the PMT gain is normal (PMT ON). The square wave drive signal can be sent at preset times or on a fixed schedule to effectively switch the PMT gain.

[0047] (2) This invention enables time gating of an anode-grounded PMT suitable for single-photon counting measurements. The time gating circuit uses the same signal line (directly connected to the drive signal input port) to receive trigger information and power supply. No additional isolated low-voltage power supply is required, which reduces complexity, size, and cost, and makes the PMT housing more ergonomic with photoluminescence spectrometers. The PMT housing requires only two inputs: its standard high-voltage power supply input and the gate drive signal input (providing trigger information and power supply) for time gating circuit operation.

[0048] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0049] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0050] Figure 1 This is a typical schematic diagram of PMT gain;

[0051] Figure 2 This is a circuit diagram of one embodiment of the control circuit of the present invention;

[0052] Figure 3 This is a circuit diagram of one embodiment of the signal generation circuit of the present invention;

[0053] Figure 4 The photomultiplier tube that did not use the control circuit of this invention was tested simultaneously with fluorescence and phosphorescence signals, and the results showed signal overlap.

[0054] Figure 5 The same sample was tested using the control circuit of this invention. Time gating eliminated the fluorescence signal, protected the PMT, and a weak phosphorescence signal was detected. Detailed Implementation

[0055] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0056] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprising" shall be understood to include the stated elements or components without excluding other elements or other components.

[0057] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0058] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0059] This invention provides an embodiment of a control circuit for an anode-grounded photomultiplier tube, such as... Figures 2 to 3 As shown, the photomultiplier tube includes a photocathode K, and connected first multiplier stage Dynode_1, second multiplier stage Dynode_2 and third multiplier stage Dynode_3. The first multiplier stage Dynode_1 is connected to the photocathode K. The control circuit also includes a square wave drive signal input port CN2, an isolation transformer XF1, a rectifier circuit and a gate circuit connected in sequence.

[0060] The drive signal input port CN2 is used to input a square wave drive signal. The primary side of the isolation transformer XF1 is connected to the drive signal input port, the middle tap of the secondary side of the isolation transformer XF1 is connected to the photocathode K, and the secondary side of the isolation transformer XF1 is connected to the rectifier circuit to supply power to the gating circuit when a square wave drive signal is received. The gating circuit is connected to the photocathode K and the third multiplier stage Dynode_3 respectively. The gating circuit is used to trigger the connection between the third multiplier stage Dynode_3 and the photocathode K based on whether there is current input: when there is current input, the gating circuit is connected to make the potential difference between the first multiplier stage Dynode_1, the second multiplier stage Dynode_2, and the third multiplier stage Dynode_3 and the photocathode K zero to reduce the PMT gain; otherwise, the connection is turned off to keep the PMT gain at the normal level.

[0061] In this invention, the first stage of the control circuit is an isolation transformer XF1. The secondary side (high-voltage side) of XF1 is connected to a -1.5kV photocathode K. When a square wave drive signal (e.g., 50kHz) is provided to the primary side of the isolation transformer XF1, the rectifier circuit smooths the current to power the circuit, triggering the gating circuit and connecting the first multiplier stage Dynode_1, the second multiplier stage Dynode_2, and the third multiplier stage Dynode_3 to the ~1.5kV photocathode K. This makes Dynode_1, Dynode_2, and Dynode_3 and the photocathode K all have the same potential, preventing electrons from multiplying through Dynode_1, Dynode_2, and Dynode_3, reducing the PMT gain by more than six orders of magnitude (PMT OFF). When the square wave drive signal is removed, the connection between the ~1.5kV photocathode K and Dynode_1, Dynode_2, and Dynode_3 is disconnected. The PMT increases back to normal levels (PMT ON).

[0062] The gating circuit of this invention uses the same signal line to receive trigger information and power supply. No additional isolated low-voltage power supply is required, which reduces complexity, size, and cost, and makes the PMT housing more ergonomic for use with photoluminescence spectrometers. The PMT housing requires only two inputs: its standard high-voltage power supply input and the gate drive signal input (providing trigger information and power) for time-gated circuit operation.

[0063] Furthermore, it also includes a signal generation circuit for connection to the square wave drive signal input port. The signal generation circuit is used to generate a square wave drive signal according to a preset timing or on-time. The signal generation circuit is as follows: Figure 3 As shown;

[0064] Furthermore, the signal generation circuit includes a field-programmable gate array (FPGA) and an operational amplifier (op-amp) circuit. The FPGA is used to generate two square wave logic signals with a specific duration and delay according to a preset value. The two square wave logic signals are inverses of each other. The op-amp circuit is used to output the two square wave logic signals as square wave drive signals.

[0065] Furthermore, the operational amplifier circuit includes a first operational amplifier U2-A and a second operational amplifier U2-B connected together; optionally, the output terminal of the first operational amplifier U2-A is connected to a first resistor R25 in parallel with the second operational amplifier U2-B; optionally, the input and output terminals of the second operational amplifier U2-B are respectively connected in series with a second resistor R24 ​​and a third resistor R21; the second resistor R24 ​​and the third resistor R21 are also connected in parallel with the first resistor R25; optionally, the first operational amplifier U2-A is also connected in parallel with a fourth resistor R40.

[0066] The first operational amplifier U2-A is used to output a square wave signal after two square wave logic signal inputs;

[0067] The second operational amplifier U2-B is used to input and output a square wave drive signal after a square wave signal.

[0068] The square wave drive signal of this invention is generated by the main control board of the spectrometer belonging to the gated PMT, using, for example... Figure 3 The signal generation circuit shown employs a Field Programmable Gate Array (FPGA) to generate two 0–+3.3V 50kHz square wave logic signals, PM_Gate_1 and PM_Gate_2, where PM_Gate_1 is the inverse of PM_Gate_2. PM_Gate_1 and PM_Gate_2 are the inputs to pins 2 and 3 of the op-amp (U2-A), outputting a + / -4.5V square wave at pin 1 of U2-A. The output signal from pin 1 of U2-A is connected to pin 5 of the op-amp buffer U2-B, providing the same output at pin 7 of U2-B. The outputs of U2-A and U2-B are connected together by 100R resistors R21 and R25, outputting at TP8, providing twice the drive current capability. The output of this circuit is the gate drive signal, provided to the gated PMT component signal input connector via a coaxial cable. When a 50kHz signal is input, the gate circuit disables the PMT gain; when no signal is present, the PMT gain returns to normal. Therefore, the switching conditions of the PMT are set using the spectrometer's control board. Gating can be controlled via the spectrometer control software. The user inputs the gate delay and gate width into the spectrometer's control software, and the FPGA on the control board generates corresponding signals for the user-specified duration and delay. The duration and timing of the PMT gating (preset via the main control board) are controlled by switching a 50kHz gate drive signal. The 50kHz gate drive signal comes from the coaxial cable of the photoluminescence spectrometer control board. Using the spectrometer's software, the gate's duration and timing are fully controllable.

[0069] Furthermore, the rectifier circuit includes a first rectifier circuit D6 and a second rectifier circuit D5;

[0070] The gated circuit includes a Schmitt trigger U1-A, an inverter U1-B, and a switching circuit connected in sequence;

[0071] The positive power supply pin 14 and negative power supply pin 7 of the Schmitt trigger U1-A are connected to the first rectifier circuit D6 and the photocathode K, respectively.

[0072] The input pin 1 and output pin 2 of the Schmitt trigger U1-A are connected to the output terminal of the second rectifier circuit D5 and the input terminal 3 of the inverter U1-B, respectively. The switching circuit is used to connect the third multiplier stage Dynode_3 to the photocathode when the input pin 1 of the Schmitt trigger U1-A is at a high logic potential, so that the first, second and third multiplier stages are at the same potential as the photocathode K.

[0073] Furthermore, it also includes a voltage regulator circuit connected between the output terminal of the first rectifier circuit D6 and the photocathode K, and a filter circuit connected between the output terminal of the second rectifier circuit D5 and the photocathode K.

[0074] Optionally, the voltage regulator circuit includes a resistor R16 and a reverse diode Z1 connected in parallel; optionally, the voltage regulator circuit ensures that the circuit voltage does not exceed 6V; optionally, a filter capacitor C1 is also connected in parallel to the voltage regulator circuit (the filter capacitor C1 and the resistor R16 can form a low-pass filter); optionally, the energy stored in the filter capacitor C1 can maintain the power supply for ~50μs.

[0075] Optionally, the filter circuit includes a tenth resistor R10 and a fourth capacitor C4 connected in parallel; optionally, a seventh resistor R7 is also connected between the second rectifier circuit D5 and the input pin of the Schmitt trigger U1-A.

[0076] Optionally, both the first rectifier circuit D6 and the second rectifier circuit D5 are half-bridge rectifier circuits. Optionally, the half-bridge rectifier circuit includes two rectifier diodes, the positive terminals of which are connected to the secondary side of the isolation transformer XF1 respectively, and the negative current is output.

[0077] Furthermore, the switching circuit includes a field-effect transistor Q3;

[0078] The output terminal of inverter U1-B is electrically connected to the photocathode K and the gate g terminal of field-effect transistor Q3, respectively; the source s terminal and drain d terminal of field-effect transistor Q3 are connected to the photocathode K and the third multiplier stage Dynode_3, respectively; this is used to trigger field-effect transistor Q3 to conduct photocathode K and the third multiplier stage Dynode_3 when a logic high potential is input to the input pin of Schmitt trigger U1-A, so that the first, second and third multiplier stages are at the same potential as photocathode K.

[0079] Furthermore, a protective resistor R3 is connected in series between the output terminal of inverter U1-B and the gate g terminal of field-effect transistor Q3; a protective resistor R5 is connected in series between the output terminal of inverter U1-B and the photocathode K; and a protective resistor R8 is connected in series between the source s terminal of field-effect transistor Q3 and the photocathode K.

[0080] Optionally, both Schmitt trigger U1-A and inverter U1-B are NOT gates. Further, Schmitt trigger U1-A is a hex-inverting Schmitt trigger.

[0081] On the other hand, a gating control method for an anode-grounded photomultiplier tube is also provided, including: inputting a square wave drive signal to the isolation transformer at regular intervals or on a timed basis to power the gating circuit; the gating circuit connects the photocathode K and the third multiplier stage to make the potential difference between the photocathode K and the second and third multiplier stages zero, so as to reduce the PMT gain; when there is no square wave drive signal input to the isolation transformer, the gating circuit is disconnected to make the PMT gain normal.

[0082] Furthermore, the square wave drive signal is generated by the signal generation circuit according to a preset timing or on a fixed schedule;

[0083] Optionally, the signal generation circuit includes a field-programmable gate array (FPGA); optionally, the FPGA generates two 0 to +3.3V 50kHz square wave logic signals with a specific duration and delay according to a preset value, and the two square wave logic signals are inverse signals of each other;

[0084] Furthermore, the gating control method is controlled by the aforementioned control circuit.

[0085] Furthermore, the gated circuit includes a Schmitt trigger U1-A, an inverter U1-B, and a field-effect transistor Q3 connected in sequence; the DC output terminal of the rectifier circuit is connected to the input pin of the Schmitt trigger U1-A; the Schmitt trigger U1-A and the inverter U1-B cooperate to trigger the field-effect transistor Q3 to conduct the photocathode K and the third multiplier stage Dynode_3 when a logic high potential is input to the input pin of the Schmitt trigger U1-A, so that the first, second, and third multiplier stages are at the same potential as the photocathode K.

[0086] Furthermore, the square wave drive signal is input to the primary side of the isolation transformer, and the middle tap of the secondary side of the isolation transformer is connected to the photocathode K. The secondary side of the isolation transformer is rectified and smoothed to supply power to the gate control circuit.

[0087] The working principle of this invention is as follows: The first stage of the time-gated circuit is an isolation transformer XF1. The secondary side (high-voltage side) of XF1 is connected to the -1.5kV cathode. When a 50kHz gate drive signal is provided to the primary side of XF1, D6 rectifies the output generated by the secondary side, C1 smooths the output, and supplies power to the circuit. Z1 ensures that the circuit voltage does not exceed ~6V and is used for U1 protection. R10 discharges the stored energy below 200µs. The secondary output of XF1 is also rectified by D5 and low-pass filters C4 and R10, and connected to the input pin of U1-A. The filter has a time constant of 1µs, which is sufficient to ensure that the input pin of U1-A is logic high. The circuit voltage rises within microseconds, supplying power to the Schmitt trigger inverter chip U1. The input switch of inverter U1-A is logic high, causing the output switch of inverter U1-B to be high, connecting Dynode_1, Dynode_2, and Dynode_3 to Q3 at the ~1.5kV cathode. Dynode_1, Dynode_2, and Dynode_3, along with the photocathode K, are now at the same potential, preventing electrons from multiplying through Dynode_1, Dynode_2, and Dynode_3, resulting in a PMT gain reduction of more than 6 orders of magnitude (PMT OFF).

[0088] When the 50kHz gate drive signal is removed, circuit U1 remains powered for ~50μs due to the energy stored in C1. Simultaneously, after removing the 50kHz gate drive signal, within a ~2µs range, the U1-A input goes low, causing the U1-B output to go low, Q3 turns off, and disconnects the ~1.5kV cathode connections Dynode_1, Dynode_2, and Dynode_3. PMT increases back to normal levels (PMTON).

[0089] The gating circuit of this invention is a time-gated circuit. It reduces the gain of the PMT with a negative high-voltage photocathode K by switching the normal voltages of the dynodes Dynode_1, Dynode_2, and Dynode_3 to the same voltage as the cathode (~1.5kV). The trigger information and power switch of the time-gated circuit are simultaneously provided by supplying a ~50kHz~10V pk-pk AC square wave (gate drive signal) to its input. When the 50kHz gate drive signal is provided at the circuit input, the time-gated circuit is powered on, and the PMT gain is reduced (PMT OFF). When no 50kHz gate drive signal is provided to the time circuit input, the time-gated circuit is unpowered, and the PMT gain is normal (PMT ON).

[0090] One of the most challenging measurement methods in photoluminescence spectroscopy is measuring the phosphorescence decay of samples that simultaneously emit fluorescence (nanosecond timescale) and phosphorescence (millisecond timescale). Thermally activated delayed fluorescence (TADF) materials, a recent hot topic in OLED research, exhibit this characteristic. Due to their short fluorescence lifetime, fluorescent photons arrive within a very short time interval after laser flash, resulting in excessive light signal reaching the phosphorescent material (PMT), causing saturation, distortion, and damage. Therefore, measuring the phosphorescence signal of such samples is extremely difficult and time-consuming. Figure 4 As shown, conventional PMT gain tubes simultaneously measure fluorescence and phosphorescence signals, resulting in signal overlap. However, using the time-gated circuit of this invention, the PMT can be time-gated, thus significantly reducing the PMT gain during fluorescence emission. This prevents PMT saturation and allows for the measurement of longer phosphorescence emission, such as… Figure 5 As shown, the control circuit can remove the fluorescence signal and protect the PMT, and a weak phosphorescence signal was detected.

[0091] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A control circuit for an anode-grounded photomultiplier tube, the photomultiplier tube comprising a photocathode, and a first multiplier stage, a second multiplier stage, and a third multiplier stage connected thereto, wherein the first multiplier stage is connected to the photocathode, characterized in that, The control circuit also includes a square wave drive signal input port, an isolation transformer, a rectifier circuit, and a gate control circuit connected in sequence. The drive signal input port is used to input a square wave drive signal; The primary side of the isolation transformer is connected to the drive signal input port, the middle tap of the secondary side of the isolation transformer is connected to the photocathode, and the secondary side of the isolation transformer is connected to the rectifier circuit to supply power to the gate control circuit when a square wave drive signal is received. The gating circuit is connected to the photocathode and the third multiplier stage respectively. The gating circuit is used to trigger the connection between the third multiplier stage and the photocathode to be turned on or off based on whether there is a current input: when there is a current input to the gating circuit, the connection is turned on so that the potential difference between the first, second and third multiplier stages and the photocathode is 0 to reduce the PMT gain; otherwise, the connection is turned off so that the PMT gain is at the normal level.

2. The control circuit for the anode-grounded photomultiplier tube according to claim 1, characterized in that, It also includes a signal generation circuit for connecting to the square wave drive signal input port, the signal generation circuit being used to generate a square wave drive signal according to a preset timing or on a timed basis.

3. The control circuit for the anode-grounded photomultiplier tube according to claim 2, characterized in that, The signal generation circuit includes a field-programmable gate array and an operational amplifier circuit; The field-programmable gate array is used to generate two square wave logic signals with a specific duration and delay according to a preset value, and the two square wave logic signals are inverse signals of each other. The operational amplifier circuit is used to output the two square wave logic signals as square wave drive signals.

4. The control circuit for the anode-grounded photomultiplier tube according to claim 1, characterized in that, The rectifier circuit includes a first rectifier circuit and a second rectifier circuit. The gated circuit includes a Schmitt trigger, an inverter, and a switching circuit connected in sequence. The positive and negative power supply pins of the Schmitt trigger are connected to the first rectifier circuit and the photocathode, respectively. The input and output pins of the Schmitt trigger are connected to the output terminal of the second rectifier circuit and the input terminal of the inverter, respectively. The switching circuit is used to connect the third multiplier stage to the photocathode when the input pin of the Schmitt trigger is at a logic high potential, so that the first, second, and third multiplier stages are at the same potential as the photocathode. And / or, the Schmitt trigger and the inverter are both NOT gates.

5. The control circuit for the anode-grounded photomultiplier tube according to claim 4, characterized in that, It also includes a voltage regulator circuit connected between the output terminal of the first rectifier circuit and the photocathode, and a filter circuit connected between the output terminal of the second rectifier circuit and the photocathode.

6. The control circuit for the anode-grounded photomultiplier tube according to claim 4, characterized in that, Both the first and second rectifier circuits are half-bridge rectifier circuits, each including two rectifier diodes, the anodes of which are connected to the secondary side of the isolation transformer.

7. The control circuit for the anode-grounded photomultiplier tube according to any one of claims 4 to 6, characterized in that, The switching circuit includes a field-effect transistor; The output terminal of the inverter is electrically connected to the photocathode and the gate g terminal of the field-effect transistor, respectively. The source (s) and drain (d) terminals of the field-effect transistor are connected to the photocathode and the third multiplication stage, respectively, to trigger the field-effect transistor to conduct the photocathode and the third multiplication stage when a logic high potential is input to the input pin of the Schmitt trigger, so that the first, second, and third multiplication stages are at the same potential as the photocathode. And / or, a protective resistor is connected in series between the output terminal of the inverter and the gate g terminal of the field-effect transistor, and between the output terminal of the inverter and the photocathode; a protective resistor is connected in series between the source s terminal of the field-effect transistor and the photocathode.

8. A gating control method for an anode-grounded photomultiplier tube, characterized in that, include: A square wave drive signal is periodically or periodically input to the isolation transformer to power the gate circuit. When the gate circuit is powered, it connects the photocathode and the third multiplier stage, so that the potential difference between the photocathode and the second and third multiplier stages is 0, thereby reducing the PMT gain. When there is no square wave drive signal input to the isolation transformer, the gate circuit is disconnected to ensure normal PMT gain. The gate control method is controlled by the control circuit described in any one of claims 1 to 7.

9. The gate control method according to claim 8, characterized in that, The square wave drive signal is generated by a signal generation circuit according to a preset timing or on a fixed time; the signal generation circuit includes a field-programmable gate array.

10. The gate control method according to claim 8 or 9, characterized in that, The gate circuit includes a Schmitt trigger, an inverter, and a field-effect transistor connected in sequence; the Schmitt trigger and the inverter work together to trigger the field-effect transistor to conduct the photocathode and the third multiplier stage when a logic high potential is input to the input pin of the Schmitt trigger, so that the first, second, and third multiplier stages are at the same potential as the photocathode. And / or, the Schmitt trigger and the inverter are both NOT gates; And / or, the square wave drive signal is input to the primary side of the isolation transformer, the middle tap of the secondary side of the isolation transformer is connected to the photocathode, and the secondary side of the isolation transformer is rectified and smoothed to supply power to the gate circuit.

Images