Photomultiplier tube signal output charge distribution circuit

Abstract

The invention provides a photomultiplier signal output charge distribution circuit, and belongs to the field of photomultiplier signal output. According to the invention, the technology that a plurality of capacitors are connected in parallel to carry out charge distribution is utilized, the anode output signal of the photomultiplier is distributed on two paths of output according to a required dynamic range, outputs in different dynamic ranges are naturally formed, and a subsequent readout electronics circuit can be matched. The circuit is simple in structure, high in reliability, good in voltage-resistant isolation performance, free of a peripheral control circuit and a feedback system, and suitable for occasions such as a space detector with high requirements for the size, weight and reliability of the circuit; according to the invention, the output linearity of the photomultiplier is maintained, the working voltage of each dynode of the photomultiplier is not influenced while the charges are distributed, and the recovery time of the photomultiplier is not influenced; output signals are of two-path same-direction models, a subsequent reading electronics circuit does not need to be additionally processed, and the photomultiplier is suitable for occasions needing two-path output of a single photomultiplier.

Description

Technical Field

[0001] The invention belongs to the field of photomultiplier tube signal output, and in particular relates to a photomultiplier tube signal output charge distribution circuit. Background Art

[0002] The photomultiplier tube is a commonly used photomultiplier tube conversion device. This device realizes the conversion of photon signals into electrical signals by utilizing the photoelectric effect of metal materials and the secondary electron emission phenomenon caused by electron acceleration hitting metal in vacuum. At the same time, it realizes 10 5 to 10 6 It has excellent amplification capabilities and is widely used in high-energy physics and nuclear medicine detection equipment.

[0003] Photomultiplier tubes often have good gain linearity when detecting weak light, and their gain stability dynamic range can reach 10 6 The dynamic range of the photomultiplier tube (PMT) far exceeds the dynamic range of the subsequent readout electronics. Therefore, adaptive control of the PMT output or dynode readout is often required. However, these methods often require complex peripheral control circuits, which can easily lead to poor PMT gain stability and prolonged saturation signal recovery time. Summary of the Invention

[0004] The present invention addresses the shortcomings of the prior art by providing a charge distribution circuit for photomultiplier tube signal output. By using parallel capacitors in conjunction with subsequent resistors for charge distribution, this circuit solves the mismatch between the dynamic range of the photomultiplier tube output and the dynamic range of the subsequent readout electronics, while avoiding the need for a complex control system. While achieving charge distribution, this circuit does not affect the operating voltage of the photomultiplier tube's dynodes or the photomultiplier tube's saturation recovery time.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a photomultiplier tube signal output charge distribution circuit, comprising: a photomultiplier tube P1, voltage divider resistors R4-R15, dynode decoupling capacitors C11-C13, an anode output resistor R1, an anode voltage stabilizing capacitors C9-C10, and output coupling capacitors C1-C8; the photomultiplier tube P1 is model PMT-R6233A-100-01, and is provided with an anode P, a cathode K, a gate G, and dynodes DY1-DY8, the anode P is connected to the output coupling capacitors C1-C8, and the cathode K is grounded; voltage divider resistors R4 and R5 are connected in series between the cathode K and the gate G, voltage divider resistors R6 and R7 are connected in series between the gate G and the dynode DY1, and voltage divider resistors R8-R14 are connected to the dynodes respectively. Between dynodes DY1 and DY2, between DY2 and DY3, between DY3 and DY4, between DY4 and DY5, between DY5 and DY6, between DY6 and DY7, and between DY7 and DY8, one end of the voltage divider resistor R15 is connected to the dynode DY8, and the other end is connected to the anode voltage-stabilizing capacitor C9; dynode decoupling capacitors C11 and C12 are connected between dynodes DY6 and DY7, and between DY7 and DY8, respectively; one end of the dynode decoupling capacitor C13 is connected to the dynode DY8, and the other end is connected to the anode voltage-stabilizing capacitor C9; anode stabilizing capacitors C9 and C10 are connected in series, and anode stabilizing capacitor C10 is grounded; one end of the anode output resistor R1 is connected to the anode P, and the other end is connected to the anode stabilizing capacitor C9.

[0007] Optionally, the output coupling capacitors C1-C8 are connected to the anode P in two ways, wherein one way is the series output coupling capacitors C1 and C2 connected in parallel with the series output coupling capacitors C3 and C4, and the other way is the series output coupling capacitors C5 and C6 connected in parallel with the series output coupling capacitors C7 and C8.

[0008] Optionally, the photomultiplier tube P1 operates in an AC pulse readout mode.

[0009] Optionally, the operating voltage of the photomultiplier tube P1 is 1250V, and the actual detection maximum signal equivalent current is 1uA.

[0010] Optionally, the DC current of the voltage-dividing resistors R4 - R15 is more than 100 times the maximum signal instantaneous pulse current when the photomultiplier tube P1 is working.

[0011] Optionally, the voltage divider resistors R4-R15 are 1 MΩ.

[0012] Optionally, the capacitance of the dynode decoupling capacitors C11-C13 is 100*Q max / V hv , Q max The anode P outputs the maximum charge signal, V hv is the supply voltage of the photomultiplier tube P1.

[0013] Optionally, the dynode decoupling capacitors C11-C13 are ceramic capacitors with a withstand voltage greater than twice the actual operating voltage.

[0014] Optionally, the anode output resistor R1 is 10KΩ.

[0015] Optionally, the withstand voltage of the anode voltage-stabilizing capacitors C9 and C10 is at least twice the actual operating voltage of the photomultiplier tube P1.

[0016] The beneficial effects of the present invention are: the present invention utilizes the technology of multiple parallel capacitors for charge distribution, and distributes the photomultiplier tube anode output signal on two outputs according to the required dynamic range, naturally forming outputs with different dynamic ranges, which can match the subsequent readout electronic circuit. The advantages of the present invention are:

[0017] 1. The circuit structure is simple, the reliability is high, the withstand voltage isolation performance is good, and there is no peripheral control circuit and feedback system. It is suitable for space probes and other occasions with high requirements on circuit volume, weight and reliability;

[0018] 2. Maintain the linearity of the photomultiplier tube output. While distributing the charge, it does not affect the working voltage of the photomultiplier tube dynode and the recovery time of the photomultiplier tube.

[0019] 3. The output signal is a two-way, same-direction model. No additional processing is required for the subsequent readout electronics circuit. It is suitable for applications requiring a single photomultiplier tube with two outputs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the schematic diagram of the charge distribution circuit for the photomultiplier tube signal output. DETAILED DESCRIPTION

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] The present invention proposes a photomultiplier tube signal output charge distribution circuit, see the attached Figure 1 , including: photomultiplier tube P1, voltage divider resistors R4-R15, dynode decoupling capacitors C11-C13, anode output resistor R1, anode voltage stabilizing capacitors C9-C10, and output coupling capacitors C1-C8. J in the figure represents the selector. Detailed descriptions of each component are as follows:

[0023] The photomultiplier tube P1 used in this circuit is the R6233 produced by Hamamatsu Corporation. Other types of photomultipliers can be used in the circuit of the present invention as long as they use an anode AC-coupled output. Photomultiplier tube P1 can be of any model and size, but it should operate in AC pulse readout mode. Photomultipliers operating in DC mode cannot use the charge distribution circuit proposed in this invention.

[0024] R4-R15 are the voltage divider resistors of the photomultiplier tube. The specific voltage divider value should be set according to the manual requirements of the corresponding photomultiplier tube. In particular, it should be ensured that the DC current on the voltage divider resistor is more than 100 times the instantaneous pulse current of the maximum signal when the photomultiplier tube is working. In the circuit of the present invention, the operating voltage of the photomultiplier tube is 1250V, and the actual detection maximum signal equivalent current is 1uA. Therefore, the DC current is selected to be greater than 100uA and the voltage divider resistor value is 1MΩ.

[0025] C11-C13 are dynode decoupling capacitors. The specific capacitance value should be set according to the manual requirements of the corresponding photomultiplier tube. Generally, the capacitance of C13 should be greater than the maximum charge signal Q output by the photomultiplier tube anode. max The photomultiplier tube supply voltage V hv The capacitance that causes 1% voltage drop is C13>100*Q max / V hv ; Each time you move forward one level, the minimum decoupling capacitance required can be halved compared to the previous level, that is, C11=0.5*C12=0.25*C13. However, in order to simplify the circuit, C11-C13 are usually set to 100*Q max / V hv Note that only ceramic capacitors can be used for C11-C13, and their withstand voltage must be greater than twice the actual operating voltage. In this circuit, since the maximum output charge of the signal to be detected is 10nC, the dynode decoupling capacitors C11-C13 are 20nF with a withstand voltage of 300V.

[0026] R1 is the anode output resistor. Its primary function is to limit the number of photoelectrons reaching the anode from returning to the power supply via the anode voltage-stabilizing capacitors C9-C10, directing them as much as possible toward the output coupling capacitors C1-C8. The resistor selection should be calculated based on the pulse rise speed of the PMT output and the equivalent impedance of the parallel capacitors (C1-C8) at the output port. In this circuit, for a PMT output signal with a rise time of 10ns, using an output coupling capacitor of 680pF to 680nF, the value of R1 should be around 10kΩ. It is important to note that the selection of the anode output resistor R1 varies depending on the type of back-end readout circuit. For circuits using voltage readout, since the resistance after the output coupling capacitors C1-C8 is very large, R1 should not be too large, as this can easily cause the PMT anode voltage to fluctuate and affect the PMT gain stability. For circuits using charge readout, since the resistance after the output coupling capacitors C1-C8 is very small, R1 should be larger to reduce the amount of charge leaking through R1 and improve the signal-to-noise ratio of the readout circuit. In the circuit of the present invention, since a charge readout method is subsequently adopted, R1 is selected to be 10KΩ.

[0027] C9-C10 are anode stabilizing capacitors, ensuring the stability of the photomultiplier tube's anode voltage while reducing potential ripple noise from the high-voltage power supply. Their value should ensure that the voltage drop across the capacitors generated by the charge generated by the maximum signal to be observed by the photomultiplier tube is less than 1% of the photomultiplier tube's supply voltage. In this circuit, a 6.8nF anode stabilizing capacitor is selected based on the actual signal size observed by the photomultiplier tube. It's important to note that the anode stabilizing capacitor's withstand voltage should be twice the actual photomultiplier tube operating voltage to avoid capacitor breakdown during operation.

[0028] C1-C8 are output coupling capacitors. By connecting capacitors of different capacitance values ​​in parallel, the output charge of the photomultiplier tube is distributed among different outputs. After connecting the same readout electronic circuit at the back end, detection capabilities with different dynamic ranges are formed. Depending on the needs, the choice of capacitors is also inconsistent. In this circuit, since the two outputs need to form a 10-fold dynamic range difference, capacitors of 6.8nF and 620pF are selected respectively. After connecting the same readout electronic chip at the back end, a dynamic range of 20pC to 10nC and a dynamic range of 2pC to 1nC are formed respectively, which can effectively match the back-end readout electronic circuit to achieve signal output with different dynamic ranges. It should be noted that the impedance seen from the anode output of the photomultiplier tube is 1 / j2πfC+R L , where f is the photoelectric output pulse frequency, C is the equivalent capacitance of the coupling capacitor, R LIf two PMT outputs with the same dynamic range are required, C1-C8 can be set to the same capacitance value. This will divide the PMT output charge evenly between the two outputs, resulting in identical signals.

[0029] If the subsequent readout circuit uses charge readout, the circuit input impedance is approximately 1-5Ω. In this case, when changing the output coupling capacitor to achieve charge distribution, the equivalent impedance of the output coupling capacitor must be above 100Ω. Based on the actual observed frequency of the photomultiplier tube anode output signal, an appropriate coupling capacitor can be selected to achieve the desired proportional distribution.

[0030] In the circuit of the present invention, the actual width of the charge signal output by the photomultiplier tube is about 10ns. By setting the two coupling capacitors to 6.8nF and 680pF respectively, a circuit with two outputs of charge signals with different dynamic ranges is realized.

[0031] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A photomultiplier tube signal output charge distribution circuit, characterized in that: include: Photomultiplier tube P1, voltage divider resistors R4-R15, dynode decoupling capacitors C11-C13, anode output resistor R1, anode voltage stabilizing capacitors C9-C10, output coupling capacitors C1-C8; the model of the photomultiplier tube P1 is PMT-R6233A-100-01, which is equipped with an anode P, a cathode K, a grid G ​​and dynodes DY1-DY8. The anode P is connected to the output coupling capacitors C1-C8, and the cathode K is grounded; the voltage divider resistors R4 and R5 are connected in series between the cathode K and the grid G, the voltage divider resistors R6 and R7 are connected in series between the grid G ​​and the dynode DY1, and the voltage divider resistors R8-R14 are connected between the dynodes DY1 and DY2, and between DY2 and DY1. One end of the voltage divider resistor R15 is connected to the dynode DY8, and the other end is connected to the anode voltage-stabilizing capacitor C9, between Y3, between DY3 and DY4, between DY4 and DY5, between DY5 and DY6, between DY6 and DY7, and between DY7 and DY8; dynode decoupling capacitors C11 and C12 are connected between dynodes DY6 and DY7, and between DY7 and DY8, respectively; one end of the dynode decoupling capacitor C13 is connected to the dynode DY8, and the other end is connected to the anode voltage-stabilizing capacitor C9; anode stabilizing capacitors C9 and C10 are connected in series, and anode stabilizing capacitor C10 is grounded; one end of the anode output resistor R1 is connected to the anode P, and the other end is connected to the anode stabilizing capacitor C9.

2. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The output coupling capacitors C1-C8 are connected to the anode P in two ways, one of which is the output coupling capacitors C1 and C2 in series connected in parallel with the output coupling capacitors C3 and C4 in series, and the other is the output coupling capacitors C5 and C6 in series connected in parallel with the output coupling capacitors C7 and C8 in series.

3. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The photomultiplier tube P1 operates in an AC pulse readout mode.

4. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The operating voltage of the photomultiplier tube P1 is 1250V, and the actual maximum detection signal equivalent current is 1uA.

5. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The DC current of the voltage-dividing resistors R4 - R15 is more than 100 times the maximum signal instantaneous pulse current when the photomultiplier tube P1 is working.

6. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The voltage dividing resistors R4-R15 are 1 MΩ.

7. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The capacitance of the dynode decoupling capacitors C11-C13 is 100*Q max / V hv , Q max The anode P outputs the maximum charge signal, V hv is the supply voltage of the photomultiplier tube P1.

8. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The dynode decoupling capacitors C11-C13 are ceramic capacitors with a withstand voltage greater than twice the actual operating voltage.

9. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The anode output resistor R1 is 10KΩ.

10. The photomultiplier tube signal output charge distribution circuit according to claim 1, wherein: The withstand voltage of the anode stabilizing capacitors C9 and C10 is at least twice the actual operating voltage of the photomultiplier tube P1.

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