Ray energy spectrum acquisition circuit applied to fluorescence reflection

Abstract

The utility model discloses a ray energy spectrum acquisition circuit applied to fluorescence reflection. The ray energy spectrum acquisition circuit comprises a refrigeration control circuit, a photodiode detector, a charge sensitive pre-amplification circuit, a second-order active filtering amplification circuit and a multichannel pulse amplitude analysis circuit, wherein the refrigeration control circuit is connected with a refrigerator arranged in the photodiode detector and is used for adjusting the low temperature of an inner cavity of the photodiode detector; the output end of the photodiode detector is connected with the input end of the charge sensitive pre-amplification circuit, and the output end of the charge sensitive pre-amplification circuit is connected with the input end of the second-order active filtering amplification circuit. And the output end of the second-order active filtering and amplifying circuit is connected with the input end of the multi-channel pulse amplitude analysis circuit. According to the utility model, weak signals collected by the photodiode detector can be rapidly collected and processed by using a fluorescence reflection method, and accurate energy spectrum data can be obtained.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of ray detection especially relates to a kind of ray spectrum acquisition circuit applied to fluorescent reflection. BACKGROUND

[0002] Ray has strong penetration, when ray is irradiated on specific object, it will penetrate object and excite to generate fluorescent ray;By detecting the intensity of penetrating object ray or analyzing the energy and intensity of fluorescent ray, the thickness of measured material can be quantitatively calculated, and it is widely used in the thickness measurement field in industry and scientific research.At present, ray transmission method is the main means;Compared with the above, the method of fluorescent reflection is often used for qualitative analysis of the type of element in material, and its application in material thickness and component quantitative analysis is not popular.

[0003] The photodiode detector for ray detection is a sensor that converts electromagnetic wave radiation into current signal.A kind of detection circuit and ray detector are disclosed in Chinese patent document with publication number CN209132439U, mainly including photodiode and front-end amplifier.

[0004] Photodiode detector usually has photovoltaic mode and photoconductive mode two working modes.Working in photovoltaic mode, photodiode does not need to add bias voltage, has lower dark current and good linearity, is suitable for higher stability requirement application, but response speed is relatively slow, which is not conducive to the output of nuclear pulse signal;While in photoconductive mode, photodiode needs to add reverse bias voltage, and the response speed of detector is significantly improved, and fast nuclear pulse signal can be outputted, but also therefore generates larger dark current, which affects signal linearity. UTILITY MODEL CONTENTS

[0005] In order to overcome the deficiencies of prior art, the utility model provides a kind of ray spectrum acquisition circuit applied to fluorescent reflection, can use the method of fluorescent reflection to the weak signal of photodiode detector acquisition is quickly collected and handled, obtains more accurate energy spectrum data.

[0006] A kind of ray spectrum acquisition circuit applied to fluorescent reflection, including refrigeration control circuit, photodiode detector, charge sensitive preamplifier circuit, second-order active filter amplifier circuit and multichannel pulse amplitude analysis circuit;

[0007] The refrigeration control circuit is connected with a refrigerator arranged in the photodiode detector, and is used for low-temperature adjustment of a cavity in the photodiode detector.

[0008] Further, a temperature measuring diode is packaged in the photodiode detector, and the temperature measuring diode is connected to the refrigeration control circuit.

[0009] The refrigeration control circuit controls a refrigeration module arranged in the photodiode detector, so as to realize low-temperature adjustment of the cavity in the photodiode detector, and ensure that the working temperature is maintained at about -30℃. The low-temperature environment can significantly reduce the generation of dark current, reduce the interference of signals, and improve the detection accuracy of the system.

[0010] Further, the charge-sensitive preamplifier circuit comprises a buffer stage circuit and an amplification stage circuit; the buffer stage circuit is composed of two JFET transistors in a common-source common-gate connection mode, and meets the requirements of high input impedance, low noise and wide frequency band; the amplification stage circuit adopts an integrated operational amplifier chip, and comprises an operational amplifier, a feedback capacitor and a bleeder resistor. The amplification stage circuit converts the input current signal into a voltage pulse signal, and can effectively improve the sensitivity and stability of the signal.

[0011] Further, a bias voltage module is connected to the charge-sensitive preamplifier circuit, and the bias voltage module is used to apply a reverse bias voltage to the power supply input of the photodiode detector.

[0012] The second-order active filter amplification circuit is used for filtering and noise reduction of the signal output by the charge-sensitive preamplifier, and simultaneously realizes signal amplification, so as to finally output the processed signal to the multi-channel pulse amplitude analysis circuit for further analysis.

[0013] Further, the second-order active filter amplification circuit comprises a first-stage filter amplification circuit and a second-stage filter amplification circuit; each filter amplification circuit comprises two resistors, two capacitors and an operational amplifier.

[0014] Further, the multi-channel pulse amplitude analysis circuit comprises an ADC acquisition circuit and an FPGA data processing circuit; the input end of the ADC acquisition circuit is connected with the output end of the second-order active filter amplification circuit; and the output end of the ADC acquisition circuit is connected with the input end of the FPGA data processing circuit.

[0015] The ADC acquisition circuit first carries out digital sampling on the pulse waveforms output by the front-end circuit, and utilizes the efficient digital signal processing algorithm of the FPGA data processing circuit to perform data conversion on the collected signals, thereby ensuring the accuracy and reliability of the analysis results, and realizing extraction, saving and transmission of the energy spectrum information.

[0016] Compared with the prior art, the utility model has the advantages of:

[0017] 1、The utility model discloses, work in light guide mode, the response speed of photodiode detector is promoted significantly, signal acquisition efficiency is higher, guarantee the inner chamber of photodiode detector is at low temperature using refrigeration control circuit, effectively reduce the interference of dark current to signal acquisition, adopt multistage amplification and multistage filter circuit, make signal can pass through further noise reduction amplification processing, thereby reduce the influence of noise and amplify signal.

[0018] 2、The utility model discloses can utilize the method of fluorescent reflection to measure the thickness of the measured material, and the measurement speed and precision are higher than the transmission method, and simultaneously, compared with the transmission method, the ray source and photodiode detection device must be installed on both sides of the measured object, and the fluorescent reflection method only needs to be installed on the same side, so that the complexity of installation operation is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a kind of principle block diagram of ray energy spectrum acquisition circuit applied to fluorescent reflection for the utility model;

[0020] Figure 2 It is the principle diagram of refrigeration control circuit in the utility model;

[0021] Figure 3 It is the principle diagram of charge sensitive preamplifier circuit in the utility model;

[0022] Figure 4 It is the principle diagram of two-order active filter amplification circuit in the utility model;

[0023] Figure 5 It is the principle diagram of multichannel pulse amplitude analysis circuit in the utility model;

[0024] Figure 6 It is the signal waveform collected by charge sensitive amplification circuit;

[0025] Figure 7 It is the energy spectrum curve collected by energy spectrum acquisition circuit. DETAILED DESCRIPTION

[0026] The utility model will be further described in detail in combination with the drawings and examples, and it should be pointed out that the following examples are intended to facilitate the understanding of the utility model, and do not have any limiting effect on it.

[0027] As Figure 1 shown, a ray energy spectrum acquisition circuit applied to fluorescent reflection includes a refrigeration control circuit 1, a photodiode detector 2, a charge sensitive preamplifier circuit 3, a second-order active filter amplifier circuit 4, a multi-channel pulse amplitude analysis circuit 5, and a bias voltage module 6.

[0028] The output end of the refrigeration control circuit 1 is connected to the input end of the refrigeration module in the photodiode detector 2, the input end of the charge sensitive preamplifier circuit 3 is connected to the output end of the photodiode detector 2, the bias voltage module 6 is connected to the charge sensitive preamplifier circuit 3, and is used to apply a reverse bias voltage to the output of the photodiode detector 2; the input end of the second-order active filter amplifier circuit 4 is connected to the output end of the charge sensitive preamplifier circuit 3, the input end of the multi-channel pulse amplitude analysis circuit 5 is connected to the output end of the second-order active filter amplifier circuit 4, and the output end of the multi-channel pulse amplitude analysis circuit 5 is connected to the input end of a PC.

[0029] As Figure 2 shown, in the refrigeration control circuit, D1 is a temperature measuring diode packaged in the photodiode detector, and is used to detect the temperature change of the current detector inner cavity in real time. The change of the inner cavity temperature will cause the change of the forward voltage drop of the temperature measuring diode D1, thereby causing the corresponding change of the voltage at the 5 pin of the input end of the operational amplifier U2B. The operational amplifier U2B is used as a voltage follower in the circuit, impedance transformation is realized, and the output end 7 pin of the operational amplifier U2B will output a voltage signal which is equal and in phase with the input end 5 pin. R2 is a temperature setting resistor, the operational amplifier U2A is used as a comparator, R2 changes the resistance size connected to the circuit, thereby changing the voltage at the reverse input end 2 pin of the operational amplifier U2A, and comparing the voltage with the voltage at the same direction input end 3 pin of U2B input to the same direction input end 3 pin of U2A. Since the reference voltage at the FB pin end of the power supply chip U1 is fixed as 1.25V, the voltage difference between the two ends of the reference resistor R6 can be changed to adjust the current on R6, and the output voltage of the power supply chip U1 can be obtained according to Ohm's law. If the set temperature is higher than the detector inner cavity temperature, the 1 pin of U2A outputs a low voltage, the DC-DC power supply chip U1 calculates that there is a large current on R6 and R7 according to the voltage difference between the two ends of R6, and calculates the corresponding high voltage at the 6 pin SW output according to Ohm's law, to control the refrigeration device to heat up; conversely, if the set temperature is lower than the detector inner cavity temperature, the 1 pin of U2A outputs a high voltage, the DC-DC power supply chip U1 calculates that there is a small current on R6 and R7 according to the voltage difference between the two ends of R6, and calculates the corresponding low voltage at the 6 pin SW output according to Ohm's law, to control the refrigeration device to cool down.

[0030] As Figure 3As shown, in the charge sensitive preamplifier circuit, HighV is the reverse bias voltage applied to the photodiode detector D3 by the external device, R4 and R5 are current limiting resistors to prevent excessive current after biasing high voltage from damaging components; C6, C7, C10, C11 are filter capacitors to filter out noise in the bias power supply and reduce the influence of the photodiode detector. The charge sensitive amplifier circuit is mainly used for the integral amplification of weak current signals. The first stage is the part most susceptible to noise. Two JFET transistors are selected and connected in a common source and gate connection mode to form an input buffer circuit. When the photodiode detector D3 is irradiated by high-energy rays, ionization occurs, and under the action of the bias voltage HighV, a weak current signal is formed. The signal passes through the coupling capacitor C4 into the gate of the transistor Q2, and the direct current signal is isolated, ensuring that the next stage of the circuit has a stable static working point. The selected operational amplifier U3A is combined with a stable precision feedback capacitor C2 and a low-noise large-value bleeder resistor R1 to form an amplification stage circuit, to ensure that the operational amplifier outputs a stable voltage within its linear operating range. R33 and R34 are bias resistors that distribute voltage to the reverse end 2 pin of the operational amplifier U3A. Figure 6 The signal waveform measured at the output end of the charge sensitive preamplifier circuit is shown. The output waveform is characterized by an exponential decay pulse signal, which meets the waveform requirements for the output of the charge sensitive preamplifier circuit.

[0031] As shown in Figure 4 The active second-order filter amplifier circuit is composed of two stages of second-order filter amplifier circuits. The RC integration network is connected to the feedback loop of the operational amplifier, so that each stage of the circuit simultaneously implements the functions of filtering and amplification. This circuit effectively combines the functions of filtering and amplification, achieving a large number of stages with fewer components, thereby simplifying the circuit structure and making it easy to implement. The shaping of nuclear pulses is usually aimed at obtaining a quasi-Gaussian pulse signal, which can improve the energy resolution and signal-to-noise ratio of the system compared to an exponential decay signal. At the same time, in multi-channel acquisition, a quasi-Gaussian pulse signal can more accurately capture the peak value of the signal. Specifically, R18, R19, C16, C18, and operational amplifier U5A constitute the first stage of the circuit with a second-order filtering effect. By adjusting the values of R18, R19, C16, and C18, the shaping time of the first-stage filter amplifier circuit can be changed. The amplification factor of the first-stage filter amplifier circuit is The second-stage filter amplifier circuit is composed of R20, R21, C17, C19, and operational amplifier U5B. Similarly, by adjusting the values of R20, R21, C17, and C19, the shaping time of the second-stage filter amplifier circuit can be changed. The amplification factor of the second-stage filter amplifier circuit is The exponential decay signal processed by the charge sensitive preamplifier circuit is input to the first-stage filter amplifier circuit and the second-stage filter amplifier circuit in sequence, and after being filtered and amplified, a quasi-Gaussian pulse waveform is output and can be used for subsequent signal processing and analysis.

[0032] As shown in Figure 5 The multi-channel pulse amplitude analysis circuit is composed of an ADC acquisition circuit and an FPGA data processing circuit. The ADC acquisition circuit is responsible for discretizing the input quasi-Gaussian pulse signal to form a digitized pulse signal for subsequent analysis and processing by the FPGA data processing circuit. In addition to the information of the signal itself, the signal input into the ADC chip also contains various frequency noises. In order to avoid signal aliasing when sampling the quasi-Gaussian pulse signal, a high-speed ADC chip with high sampling frequency is used, and differential signal input is adopted to preserve the information in the signal as completely as possible. Since the input quasi-Gaussian pulse signal is a single-ended signal, a single-ended-to-differential driving chip U7 is used for the differential input high-speed ADC. The single-ended signal is converted into a differential signal by the single-ended-to-differential driving chip U7. The differential signal at the same phase is input to the VIN+ terminal of the ADC chip U6 through R30, and the differential signal at the opposite phase is input to the VIN- terminal of the ADC chip U6 through R28. The ADC chip U6 processes the input analog differential signal and converts it into a discrete digital signal, which is output to the FPGA chip for subsequent data processing and analysis.

[0033] The quasi-Gaussian pulse signal input into the ADC chip U6 is discretized into digital signals of different sizes according to the different amplitudes of the waveform. The values of these digital signals are stored in the corresponding memory of the FPGA according to their sizes. If the same digital signal value is collected, the corresponding memory count is incremented by 1. After a certain time of radiation collection, the values of each digital signal in the memory and the corresponding digital signal count value are derived, and the curve fitted according to the values of the digital signals and the corresponding digital signal count values is the energy spectrum curve.

[0034] The utility model discloses a SI-PIN photoelectric detector of 6mm 2 The utility model discloses a SI-PIN photoelectric detector of 6mm Figure 7 The utility model discloses a SI-PIN photoelectric detector of 6mm Figure 7It can be seen that the collected energy spectrum curve is relatively smooth and has less noise; the other two copper foils with different thicknesses are tested by fluorescence reflection, and the obtained results are consistent with the theoretical results, and with the increase of the thickness, the fluorescence intensity also increases; under the test condition, a plurality of groups of data are collected, and the feedback results of the plurality of groups of data show that the stability of the energy spectrum collection is good; 5 groups of data are collected under the conditions that the sampling time is 1s, 2s, 4s, 6s and 8s respectively, and the feedback data results show that with the proportional increase of the sampling time, the fluorescence intensity value calculated according to the energy spectrum is also increased proportionally, and the sampling time and the fluorescence intensity value are approximately linearly related. The above test results also verify the effectiveness and availability of the ray energy spectrum collection circuit applied to fluorescence reflection.

[0035] The above-described embodiments describe the technical solutions and beneficial effects of the present application in detail, and it should be understood that the above-described embodiments are only specific embodiments of the present application and are not used to limit the present application, and any modifications, supplements and equivalent replacements made within the principle range of the present application should be included in the protection range of the present application.

Claims

1. A ray energy spectrum acquisition circuit applied to fluorescent reflection, characterized in that, The application relates to a refrigeration control circuit (1), a photodiode detector (2), a charge-sensitive preamplifier circuit (3), a second-order active filter amplifier circuit (4) and a multi-channel pulse amplitude analysis circuit (5). The refrigeration control circuit (1) is connected with a refrigerator arranged in the photodiode detector (2) and is used for low-temperature adjustment of a cavity in the photodiode detector (2); the output end of the photodiode detector (2) is connected with the input end of the charge-sensitive preamplifier circuit (3), the output end of the charge-sensitive preamplifier circuit (3) is connected with the input end of the second-order active filter amplifier circuit (4), and the output end of the second-order active filter amplifier circuit (4) is connected with the input end of the multi-channel pulse amplitude analysis circuit (5).

2. The ray energy spectrum acquisition circuit applied to fluorescent reflection according to claim 1, characterized in that, The photodiode detector (2) is packaged with a temperature measuring diode, and the temperature measuring diode is connected with the refrigeration control circuit (1).

3. The ray energy spectrum acquisition circuit applied to fluorescent reflection according to claim 1, characterized in that, The charge-sensitive preamplifier circuit (3) comprises a buffer stage circuit and an amplification stage circuit.

4. The ray energy spectrum acquisition circuit applied to fluorescent reflection according to claim 1, characterized in that, The charge-sensitive preamplifier circuit (3) is connected with a bias voltage module (6), and the bias voltage module (6) is used for applying a reverse bias voltage to a power supply input of the photodiode detector (2).

5. The ray energy spectrum acquisition circuit applied to fluorescent reflection according to claim 1, characterized in that, The second-order active filter amplifier circuit (4) comprises a first-stage filter amplifier circuit and a second-stage filter amplifier circuit, and each filter amplifier circuit comprises a resistor, a capacitor and an operational amplifier.

6. The ray energy spectrum acquisition circuit applied to fluorescent reflection according to claim 1, characterized in that, The multi-channel pulse amplitude analysis circuit (5) comprises an ADC acquisition circuit (51) and an FPGA data processing circuit (52). The input end of the ADC acquisition circuit (51) is connected with the output end of the second-order active filter amplifier circuit (4), and the output end of the ADC acquisition circuit (51) is connected with the input end of the FPGA data processing circuit (52).

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