Differential mode signal processing system of liquid scintillation spectrometer

Abstract

The utility model discloses a liquid scintillation spectrometer differential mode signal processing system, which is characterized in that the system comprises N detectors, a differential mode amplification circuit, a conversion circuit and an FPGA chip, the differential mode amplification circuit comprises N instrument amplification modules, the N detectors are electrically connected with the differential mode amplification circuit through a resistance-capacitance filter circuit, and the conversion circuit is electrically connected with the FPGA chip through the resistance-capacitance filter circuit. And each differential mode amplification circuit is connected in parallel with the reference zero-potential operational amplifier circuit. According to the utility model, photoelectrons are output in the form of differential signals, and N paths of differential mode signals are converted into digital signals which can be identified by the FPGA chip through the comparison circuit, so that N-tube coincidence judgment, two-tube coincidence judgment, single-tube judgment and counting, digital multi-channel functions and the like are completed, and the extraction of energy amplitude is realized; compared with a traditional liquid flashing device which needs circuit processing such as complex signal adjustment, multi-stage amplification, alignment, discrimination and peak holding, the liquid flashing device is more economical, efficient, stable and reliable.

Description

TECHNICAL FIELD

[0001] The utility model relates to nuclear radiation measurement technical field especially relates to a liquid scintillation spectrometer difference mode signal processing system. BACKGROUND

[0002] In the nuclear radiation measurement industry, liquid scintillation spectrometer as a kind of beta ray detection equipment, has extensive application, such as archaeological judgment article age, nuclear waste water radioactivity detection, marine product nuclear pollution detection, medical examination and so on has irreplaceable position.

[0003] Liquid flash mainly consists of two parts: one is the counting function part of the statistical signal pulse number, two is the multichannel function part of extracting signal pulse amplitude. Counting function needs to identify as many real signals as possible, and multichannel function needs to extract the amplitude of real signal as accurately as possible. Due to the characteristics of the measurement method used by liquid flash, the continuous energy spectrum diagram with energy amplitude starting from zero to the maximum energy of the measured nuclide is distributed according to certain rules. Therefore, the signal amplitude near absolute zero amplitude will inevitably be overwhelmed by noise, and the larger the signal amplitude, the smaller the possibility of signal being overwhelmed by noise, and the higher the detection efficiency.

[0004] The detector design of traditional liquid flash mostly uses general photomultiplier tube design, and the general photomultiplier tube design is single-ended output. Single-ended output refers to taking reference ground as zero potential, and the output signal either changes to positive polarity, called positive signal, or changes to negative polarity, called negative signal, both positive signal and negative signal are single-ended output signals. As shown in Figure 2 Since the three detectors 3 need to be fixed at a certain angle and installed close to the measured sample 2, the output signal of the photomultiplier tube often needs to be output to a certain distance to the signal processing unit, and generally needs to be wired for 2-3 meters. The signal line is easy to be affected by electromagnetic interference when wired in the air. In order to avoid such electromagnetic interference, most liquid flash manufacturers use high-speed shielded wire for output, relying on the ground shielding layer to resist external electromagnetic interference, but since the system is grounded on a large area, noise can be easily introduced through the ground wire, resulting in a large basic noise. When the signal passes through the multichannel function to extract the amplitude, the noise superimposed on the signal will affect the accuracy of amplitude extraction. The traditional liquid flash design has to be isolated, adjusted, amplified, coupled and a series of circuit designs to regulate the signal quality in actual hardware implementation. Therefore, the basic noise of the signal of the traditional liquid flash design increases continuously with the generation and transmission of the signal, and only the noise reduction ability is left for the counting function and the multichannel function, without the ability to offset the noise.

[0005] For the above reasons, the traditional liquid flash design often has to improve the performance of the photomultiplier tube, select a photomultiplier tube with high amplification and good energy linearity, use the high performance of the photomultiplier tube to improve the signal-to-noise ratio, and achieve the purpose of collecting more signals in the low energy region, but this increases the cost and the difficulty of selecting the photomultiplier tube.

[0006] In addition, the traditional liquid flash design always encounters difficulty in distinguishing when performing the alpha-beta separation function. The alpha-beta separation function is that when the detector measures a sample, it may receive an alpha signal or a beta signal, at which time the liquid flash device should have the function of distinguishing the two signals and separating them on the spectrum. Due to the characteristics of the liquid flash device, the alpha-beta signals are continuous, and therefore there is a place of overlap on the spectrum. In the alpha-beta separation function, it is often difficult to distinguish the alpha-beta signals with close amplitudes, and when the amplitudes of the alpha-beta signals are the same, the signal characteristics differ very little and are difficult to distinguish. The traditional design often improves the degree of distinction by integration, logarithmic transformation and other algorithms.

[0007] Therefore, how to provide an efficient, accurate, stable and economical liquid scintillation spectrometer signal processing system is a technical problem to be solved at present. SUMMARY

[0008] In order to solve the problems of the prior art, the utility model provides a liquid scintillation spectrometer differential mode signal processing system, N path detector, differential mode amplification circuit, conversion circuit and FPGA chip, can the light electron that captures is outputted in the mode of differential signal, through comparison circuit N path differential mode signal is converted into the digital signal that can be recognized by FPGA (Field Programmable Gate Array, field programmable logic gate array) chip, and through the addition circuit N path differential mode signal is added and N tube total energy amplitude is obtained, the signal obtained by comparison circuit uses FPGA chip as processor to complete N tube coincidence judgment, two tube coincidence judgment and single tube judgment count, and N tube total energy amplitude is processed by high speed ADC and FPGA composed digital multichannel function, thereby realizing the extraction of energy amplitude. Compared with the traditional liquid flash device which needs to be processed by complex signal adjustment, multistage amplification, alignment, discrimination and peak holding circuit, the utility model is more economical, efficient, stable and reliable.

[0009] The utility model embodiment provides the following scheme:

[0010] The utility model discloses an embodiment provides a kind of liquid scintillation spectrometer difference mode signal processing system, including N-way detector, still including difference mode amplification circuit, conversion circuit and FPGA chip, wherein difference mode amplification circuit includes N each with N-way detector electric connection's instrument amplification module, N-way detector is electrically connected between difference mode amplification circuit through resistance-capacitance filter circuit, each difference mode amplification circuit and reference zero potential operational amplifier circuit are in parallel.

[0011] The conversion circuit includes two operational amplifier modules connected to the output end of each instrument amplification module, namely a first operational amplifier module and a second operational amplifier module.

[0012] The ADC module uses a high-speed ADC chip.

[0013] The N-way detector, resistance-capacitance filter circuit and difference mode amplification circuit are connected by a shielded twisted pair.

[0014] The signal superposition module and the FPGA chip are electrically connected through a first operational amplifier module.

[0015] N is 3 or 4.

[0016] The utility model has the beneficial effects based on the technical scheme:

[0017] (1) The liquid scintillation spectrometer difference mode signal processing system provided by the utility model is provided with a resistance-capacitance filter circuit as a preamplifier circuit. The photomultiplier tube of the detector processes the output differential signal through the preamplifier. The difference mode signal is a positive and negative signal with equal magnitude and opposite polarity relative to the reference zero potential. The counting function, αβ separation function and multi-channel function of the liquid scintillation spectrometer are improved. In addition, the signal can be transmitted to the signal processing board through a shielded twisted pair. The magnetic fields around the signal lines cancel each other out to avoid mutual interference. The transmission noise and electromagnetic interference noise of the signal can be directly suppressed, and the signal quality is improved.

[0018] (2) When there is interference through the line, common mode noise will be generated on the difference mode signal pair. The common mode interference refers to the simultaneous signal increase or decrease of the two signal lines in the twisted pair. The interference from the ground into the signal is always superimposed on the difference mode signal to form common mode interference. The liquid scintillation spectrometer difference mode signal processing system provided by the utility model uses an instrument amplification circuit constructed by a differential operational amplifier. The signal positive and negative input ends are subtracted and amplified. The output signal amplitude of the difference mode signal after passing through the instrument amplification circuit is equal to the sum of the positive and negative signal amplitudes. The output signal of the common mode signal after passing through the instrument amplification circuit is cancelled out. The size of the signal itself can be improved, and the noise interference can be suppressed, thereby ensuring the continuity of the difference mode anti-interference.

[0019] (3) The utility model provides a kind of liquid scintillation spectrometer difference mode signal processing system, using operational amplifier reconstructs a reference zero potential, make the signal reference point of entire differential system and reference ground potential isolate, compared with the reference ground potential of prior art liquid flash using as signal reference, reference zero potential can effectively isolate the interference of large area using reference ground potential and string, further resist signal noise interference.

[0020] (4)The utility model provides a kind of liquid scintillation spectrometer difference mode signal processing system, three-way difference mode signals can be converted into digital signal that can be recognized by processor (FPGA chip) by comparison circuit, three-way difference mode signals are added to obtain three-tube total energy amplitude by adding circuit.The signal obtained by comparison circuit uses FPGA as processor to complete three-tube coincidence determination, two-tube coincidence determination and single tube determination count, and three-tube total energy amplitude is processed by the digital multichannel function of ADC and FPGA, thereby realizing the extraction of energy amplitude.The so-called coincidence is the process of judging whether the current received signal is the nuclear radiation signal of the measured sample, when only one photomultiplier tube receives signal at the same time, it is called single tube coincidence, when two photomultiplier tubes receive signal at the same time, it is called two-tube coincidence, and when three photomultiplier tubes receive signal at the same time, it is called three-tube coincidence.Compared with the traditional liquid flash complex signal adjustment, multistage amplification, alignment, discrimination and peak holding circuit processing, the utility model is more economical and efficient and more stable and reliable. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present specification, and other drawings can also be obtained by those skilled in the art without creative labor.

[0022] Figure 1 The liquid scintillation spectrometer difference mode signal processing system module connection schematic diagram provided for embodiment one.

[0023] Figure 2 The detector structure schematic diagram of embodiment one.

[0024] Figure 3 The circuit connection schematic diagram of liquid scintillation spectrometer difference mode signal processing system provided for embodiment one.

[0025] Figure 4 The signal processing process schematic diagram of embodiment one.

[0026] Figure 5 The detector structure schematic diagram of embodiment two.

[0027] In the figure: 1-sample chamber, 2-sample to be measured, 3-detector, 3.1.1-resistor-capacitor filter circuit, 3.1.2-differential mode amplification circuit, 3.1.3-reference zero potential operational amplifier circuit, 3.2.1-first operational amplifier module, 3.2.2-second operational amplifier module, 3.3.1-signal superposition module, 3.4.1-first-stage operational amplifier module. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art belong to the protection scope of the embodiments of the utility model.

[0029] Embodiment one

[0030] The embodiment provides a liquid scintillation spectrometer differential mode signal processing system, which is characterized by comprising three-way detectors, further comprising a differential mode amplification circuit 3.1.2, a conversion circuit and an FPGA chip, wherein the differential mode amplification circuit comprises three instrument amplification modules, namely a first instrument amplification module, a second instrument amplification module and a third instrument amplification module, which are electrically connected with the three-way detectors, the three-way detectors and the differential mode amplification circuit are electrically connected through a resistor-capacitor filter circuit 3.1.1, and each differential mode amplification circuit is connected with a reference zero potential operational amplifier circuit 3.1.3 in parallel.

[0031] The conversion circuit comprises two operational amplifier modules, namely a first operational amplifier module 3.2.1 and a second operational amplifier module 3.2.2, which are connected with the output ends of each instrument amplification module, wherein the three first operational amplifier modules are connected with the FPGA chip, and the three second operational amplifier modules are electrically connected with the FPGA chip in sequence through a signal superposition module 3.3.1 and an ADC module.

[0032] The ADC module adopts a high-speed ADC chip.

[0033] The three-way detectors, the resistor-capacitor filter circuit and the differential mode amplification circuit are connected through shielded twisted pair wires.

[0034] The signal superposition module and the FPGA chip are electrically connected through a first-stage operational amplifier module 3.4.1.

[0035] REFERENCE Figure 4The signal processing process of the embodiment is as follows: the signals output by the three detectors are Vi(A+) and Vi(A-), Vi(B+) and Vi(B-), and Vi(C+) and Vi(C-), which are processed by the resistance-capacitance filter circuit 3.1.1, input to the signal input end of the corresponding differential mode amplification circuit 3.1.2 (an instrument amplification module is used in the embodiment), and then output from the output end of the instrument amplification module to obtain Vo1(A)=(Vi(A+)-Vi(A-))*G. Since A+ and A- are equal in size and opposite in direction, Vo1=2*Vi*G, which is equivalent to doubling the original signal Vo1' = Vi*G of the traditional liquid flash device. The reference zero potential operational amplifier circuit 3.1.3 uses an operational amplifier to reconstruct a reference zero potential, so that the signal reference point of the whole system is isolated from the reference ground potential. Compared with the traditional liquid flash that uses the reference ground potential as the signal reference, the reference zero potential can effectively isolate the interference caused by the use of the reference ground potential in a large area, and further resist signal noise interference. The subsequent circuit divides Vo1 into two paths for processing, one path is used for counting after comparison by the first operational amplifier module 3.2.1, and the other path is subjected to signal following processing by the second operational amplifier module 3.2.2, and then added to the signals subjected to following processing by the other two paths through the signal superposition module 3.3.1. The added signal Vo2=Vo1(A)+Vo1(B)+Vo1(C). Since the three detectors are completely symmetrically placed, the signal amplitudes of the three tubes should be theoretically the same. When the three tubes are consistent, Vo2=3Vo1; when two tubes are consistent, Vo2=2Vo1; and when only one tube is consistent, Vo2=Vo1. Finally, the circuit is adjusted by the first operational amplifier module 3.4.1 and then input to the ADC chip for amplitude extraction. After the above circuit processing, it can be concluded that when the ADC samples a signal amplitude, the corresponding count can be obtained in the ABC three-path count. If the ABC three tubes have counts, the FPGA adds one to the three-tube consistent count at the channel number; if AB or BC or AC has counts, the FPGA adds one to the two-tube consistent count at the channel number; and if only A or B or C has counts, the FPGA records the single-tube count and adds one. The channel number refers to that the full range amplitude of the ADC is divided into n continuous regions, which are numbered 0-n-1, i.e., the channel number.

[0036] The utility model can be implemented by increasing or reducing the photomultiplier tube detector to achieve different applications and effects; it is also possible to increase the number of analog-to-digital converters (ADCs) to obtain more amplitude information of the detector signals and increase the function; it is also possible to use better devices, FPGAs and chips to replace to achieve better effects.

[0037] Embodiment two

[0038] Reference Figure 5The schematic diagram of the four-way detector structure is shown in FIG. 3. The embodiment is different from the embodiment one in that the number of the differential mode amplification circuit 3.1.2, the first operational amplifier module 3.2.1 and the second operational amplifier module 3.2.2 is increased to four, and then the four-way signal is added.

[0039] Those skilled in the art will understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can be in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can be in the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.

[0040] The present application is described with reference to flowcharts and / or block diagrams of the methods, devices (modules, systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The devices for implementing the functions specified in one or more flows and / or blocks.

[0041] These computer program instructions can also be stored in a computer-readable memory capable of guiding the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction devices, which implement the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The devices for implementing the functions specified in one or more flows and / or blocks.

[0042] These computer program instructions can also be loaded into a computer or other programmable data processing device, so that a series of operation steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The devices for implementing the functions specified in one or more flows and / or blocks.

[0043] While the preferred embodiments of the application have been described, those skilled in the art will recognize that the application can be practiced with modification and alteration within the spirit and scope of the application. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive. The scope of the application is indicated by the appended claims, rather than by the foregoing description.

[0044] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the application can be practiced otherwise than as specifically described.

Claims

1. A differential mode signal processing system for a liquid scintillation spectrometer, characterized in that, The device includes N detectors and is characterized by further including a differential amplifier circuit (3.1.2), a conversion circuit, and an FPGA chip. The differential amplifier circuit includes N instrumentation amplifier modules that are electrically connected to the N detectors respectively. The N detectors are electrically connected to the differential amplifier circuit through an RC filter circuit (3.1.1). Each differential amplifier circuit is connected in parallel with a reference zero-potential operational amplifier circuit (3.1.3).

2. The differential mode signal processing system for a liquid scintillation spectrometer according to claim 1, characterized in that: The conversion circuit includes two operational amplifier modules connected to the output of each instrument amplification module, namely the first operational amplifier module (3.2.1) and the second operational amplifier module (3.2.2). N first operational amplifier modules are connected to the FPGA chip, and N second operational amplifier modules are electrically connected to the FPGA chip in sequence through the signal superposition module (3.3.1) and the ADC module.

3. The differential mode signal processing system for a liquid scintillation spectrometer according to claim 1, characterized in that: The ADC module uses a high-speed ADC chip.

4. The differential mode signal processing system for a liquid scintillation spectrometer according to claim 1, characterized in that: The N-channel detectors, RC filter circuits, and differential amplifier circuits are connected by shielded twisted-pair cables.

5. The differential mode signal processing system for a liquid scintillation spectrometer according to claim 1, characterized in that: The signal superposition module and the FPGA chip are electrically connected through a first-stage operational amplifier module (3.4.1).

6. The differential mode signal processing system for a liquid scintillation spectrometer according to claim 1, characterized in that: N is 3 or 4.

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