CN118671812A

CN118671812A - Series readout circuit of nuclear radiation detector and position identification method

Info

Publication number: CN118671812A
Application number: CN202410825898.XA
Authority: CN
Inventors: 杨剑; 曾国强; 李欣月; 邓皓文; 胡传皓; 杨新宇; 田成帅; 欧阳晓平
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2024-06-25
Filing date: 2024-06-25
Publication date: 2024-09-20

Abstract

The invention relates to the technical field of nuclear radiation detection, and discloses a series readout circuit and a position identification method of a nuclear radiation detector, wherein the series readout circuit comprises a series shunt resistor network, charge sensitive preamplifiers positioned at two ends of the series shunt resistor network and a common line; the series shunt resistor network comprises n detectors connected to the common line; a shunt resistor R is arranged between every two adjacent access points of the detectors connected to the common line, and the number of the shunt resistors R is n-1; the single charge sensitive preamplifier comprises an operational amplifier G, a feedback capacitor C _f and feedback resistors R _f,C_f and R _f which are all connected in parallel with the negative input end and the negative output end of the operational amplifier G. Compared with the traditional multichannel read-out electronics, the invention greatly reduces the number of channels of the electronics, only comprises 2 channels, improves the signal-to-noise ratio, reduces the electronic power consumption, and realizes the rapid positioning of the response detector to realize accurate position identification.

Description

Series readout circuit of nuclear radiation detector and position identification method

Technical Field

The invention relates to the field of nuclear radiation detection, in particular to a series readout circuit of a nuclear radiation detector and a position identification method.

Background

In recent years, with the rapid development of modern nuclear industry, nuclear detection technology, which is an important research point in the field of nuclear energy, is widely used in the fields of medical imaging, physics, military, energy, and the like. At the same time, nuclear security is also becoming a topic of increasing concern. The detection and accurate positioning of nuclear radiation are critical to nuclear safety, nuclear security measures, environmental monitoring and homeland security. With the progress of nuclear industry technology, the nuclear radiation detector can accurately identify and position the radioactive source in a wide field of view, and radiation detection efficiency is greatly improved. How to process the nuclear pulse signal output by the detector is an important research field.

Currently, the following approaches exist for conventionally processing nuclear pulse signals for nuclear radiation detection:

1. the nuclear radiation detector is used for carrying out signal reading circuit through the charge sensitive preamplifier, then carrying out multichannel pulse amplitude analyzer, simulating multichannel including zero cancellation, filtering forming, peak value holding, entering low-speed ADC (analog to digital converter) sampling, and finally carrying out design processing on a processor. The pulse signal output by the detector is processed by adopting an analog circuit to complete the function of analyzing the amplitude of the multi-channel pulse, and the energy spectrum is obtained.

2. The nuclear radiation detector acquires pulse waveforms through a signal readout circuit of the charge sensitive preamplifier by means of a high-speed ADC, performs trapezoidal shaping, pulse waveform discrimination, baseline recovery, pulse anti-accumulation, pulse amplitude analysis and other treatments through a digital signal processing circuit, and finally acquires energy spectrum.

The nuclear radiation detector converts radiation into electrical signals, which are processed by a charge-sensitive preamplifier. Common nuclear radiation detectors are gas ionization detectors, semiconductor detectors, scintillator detectors, and the like. The scintillator detector can be widely applied to various common radiation detection fields including security check, industrial detection, space detection, medical imaging and the like, and is also a nuclear radiation detector which is more widely applied.

In the nuclear radiation detection system, the output signal amplitude of the detector of the preamplifier readout circuit is smaller, so that the signal of the detector needs to be amplified by matching with a preamplifier circuit. The core pre-amplifying circuit of the nuclear radiation detector mainly comprises 3 types of charge sensitivity, voltage sensitivity and current sensitivity. Because of the advantages of the charge-sensitive pre-amplification circuit in gain stability and noise performance, the charge-sensitive pre-amplification circuit is widely applied to the field of nuclear radiation detection. When selecting the core op-amp chip of the charge-sensitive preamplifier circuit, the op-amp chip is typically required to have sufficient gain, high bandwidth, and as little current noise as possible.

When nuclear radiation detectors are used for radiographic imaging, a large number of detectors are required, typically with separate readout circuits for each detector to ensure detection performance. If the four-corner signal reading is performed by adopting a transverse and vertical resistor shunt mode, the number of channels of reading electronics can be greatly reduced, but charge loss can be caused by charge shunt, and the amplitude of an output signal can be attenuated. At the same time, the multi-channel electronics share also increases noise, thereby affecting energy resolution.

Disclosure of Invention

In order to overcome or alleviate one or more of the above technical problems, the present invention aims to provide a serial readout circuit and a position identification method for a nuclear radiation detector, which can solve the problem that the number of readout electronic circuits for a plurality of detectors and a plurality of channel circuits is large, reduce the number of readout electronic channels by using the serial readout circuit, ensure better energy resolution, and identify the positions of the detectors by using the amplitude and time information of two read signals which are forwarded.

The invention provides the following technical scheme:

In a first aspect, the present invention provides a series readout circuit of a nuclear radiation detector, comprising a series shunt resistor network, charge-sensitive preamplifiers located across the series shunt resistor network, and a common line; the series shunt resistor network comprises n detectors connected to the common line, wherein the detectors are used for nuclear radiation detection, and n is a natural number greater than 2; a shunt resistor R is arranged between every two adjacent access points of the detectors connected to the common line, and the number of the shunt resistors R is n-1; the single charge sensitive preamplifier comprises an operational amplifier G, a feedback capacitor C _f, a feedback resistor R _f,C_f and a feedback resistor R _f which are connected in parallel with negative input and output ends of the operational amplifier G, and the two operational amplifiers are G ₁ and G ₂ respectively.

In the above embodiment, for a series readout circuit of nuclear radiation detectors, the structural features include n (n > 2) nuclear radiation detectors, 2 charge-sensitive preamplifiers, and n-1 shunt resistors R. The charge sensitive preamplifier is composed of an operational amplifier G ₁、G₂, a feedback capacitor C _f and a feedback resistor R _f. The detector may be directly connected to the shunt resistor by a wire or may be ac coupled to the shunt resistor by a capacitor. And then the detector is connected to two charge sensitive preamplifiers in series through a wire to realize the split-flow reading S ₁(t)、S₂ (t) of the charge signals generated by the detector. The series readout circuit reduces the number of channels of readout electronics and ensures better charge collection, thereby improving the signal-to-noise ratio of the readout signal.

According to some embodiments, an ac-coupled capacitor C is also connected before the probe is connected to the common line.

In the above embodiment, the coupling manner of the detector and the shunt resistor is divided into direct coupling and alternating coupling. The direct coupling is to directly connect the pulse signal output by the detector to the input end of the operational amplifier. The AC coupling is to remove the DC offset of the detector output and connect the input end of the operational amplifier through the capacitor.

In a second aspect, the present invention provides a method for identifying the position of a series readout circuit of a nuclear radiation detector as described above, characterized by: the method sequentially comprises the following steps of:

S0, assembling a series readout circuit: firstly, assembling the series shunt resistor network, which comprises n detectors connected to the common line; a shunt resistor R is arranged between every two adjacent access points of the detectors connected to the common line, and the number of the shunt resistors R is n-1; two charge sensitive preamplifiers are respectively arranged at two ends of a common line of the assembled series shunt resistor network, and the power supply mode of the two charge sensitive preamplifiers is double-power supply or single-power supply;

S11, detection output signals S ₁ (t) and S ₂ (t): detecting output signals of two charge-sensitive preamplifiers, wherein the two signals represent responses of two ends of the detector, the two charge-sensitive preamplifiers respectively output signals S ₁(t)、S₂ (t), and the signal waveforms of the two charge-sensitive preamplifiers are exponentially decaying signals;

S12, calculating the amplitude of an output signal S ₁(t)、S₂ (t) for extracting amplification coefficients, namely A ₁ and A ₂ respectively, wherein the calculation formula is as follows:

Wherein B ₁、B₂ is a constant, A ₁、A₂ is an amplification factor of the operational amplifier, and B ₁、B₂ constant is determined by parameters of the detector; i is the serial number of a specific shunt resistor;

s13, calculating a ratio F of the single read signal amplitude to the total amplitude of the two read signals according to the following formula:

S14, determining the relation between the ratio F and the position: under the known position, the direct relation between the position and the ratio is obtained through simulation and a large number of experiments, wherein the large number of experiments are that the steps S11-S13 are circularly executed until the range of the ratio F corresponding to different detector positions is determined, and a relation chart of the detector positions and the ratio F is established;

S15, determining the position of a detector: in the formal measurement, the ratio F of the current signal is measured by executing S11-S13, and the position of the detector is determined by using the relation chart established in the step S14.

In the above embodiment, the signal amplitude of the output signal S ₁(t)、S₂ (t) is calculated for extracting the amplification factor a ₁、A₂, and then position recognition is performed using a ₁、A₂. Determining the range of the ratio F of different detector positions through a large number of tests based on the magnitudes of the output signals of the two charge sensitive amplifiers, wherein F is the ratio of the single-ended read-out signal amplitude to the total amplitude of the two read-out signals; the position of the detector is then determined by measuring the relation of the ratio F to the detector position determined in advance to the ratio F. The readout method directly processes the analog signal at the back end of the amplifier, providing better charge collection while minimizing the noise contribution of the resistive readout chain.

According to some embodiments, the method further comprises a correction step S3, specifically as follows:

S31, according to the step S12, obtaining actual test energy E _pi in the obtained energy peak diagram, wherein the standard energy of each radioactive source is different from the standard energy of the radioactive source E _r, the standard energy of the same radioactive source is the same, and corresponding actual test energy E _p is recorded;

S32, obtaining a correction coefficient K _i and an offset a _i, performing linear regression on each position i by using standard energy E _r and actual test energy E _pi, obtaining a correction coefficient K _i and an offset a _i, matching the relation chart established in the step S14, and establishing a corresponding correction relation chart; matching the measured ratio F with a pre-established relation chart to find the nearest position i;

and S33, compensation calculation, namely performing accurate correction:

According to the position i matched in S32, the actual test energy E _pi is corrected by using the corresponding correction coefficient K _i and the offset a _i, and the correction formula is as follows:

E_r＝K_i·E_pi+a_i (7)

The corrected energy E is equal to the standard energy E _r.

In a third aspect, the present invention also provides a method for identifying the position of a series readout circuit of a nuclear radiation detector as described above, comprising the following steps in order:

s0, assembling a series readout circuit: firstly, assembling the series shunt resistor network, which comprises n detectors connected to the common line; a shunt resistor R is arranged between every two adjacent access points of the detectors connected to the common line, and the number of the shunt resistors R is n-1; two charge sensitive preamplifiers are respectively arranged at two ends of a common line of the assembled series shunt resistor network, and the power supply of the two charge sensitive preamplifiers is selected to be supplied with power by double power supplies;

S21, detection output signals S ₁ (t) and S ₂ (t): detecting output signals of two charge-sensitive preamplifiers, wherein the two signals represent responses of two ends of the detector, and the two charge-sensitive preamplifiers respectively output signals S ₁(t)、S₂ (t);

S22, extracting rising time tau ₁ and tau ₂: according to the rising time of the output signal S ₁(t)、S₂ (t), directly reading the time period from the baseline to the peak value of the measurement signal or respectively marking the time constants as tau ₁ and tau ₂ by calculation, wherein the calculation formula is as follows;

τ₁＝R_f·C_f·(k-1) (3)

τ₂＝R_f·C_f·(n-k) (4)；

s23, ratio T: the ratio T of the rise time of a single read signal to the total rise time of two read signals is calculated as follows:

S24, determining the relation between the ratio T and the position: under the known position, the direct relation between the position and the ratio is obtained through simulation and a large number of experiments, wherein the large number of experiments are that the steps S21-S23 are circularly executed until the range of the ratio T corresponding to different detector positions is determined, and a relation chart of the detector positions and the ratio T is established;

S25, determining the position of a detector: in the formal measurement, the ratio T of the current signal is measured by executing S21-S23, and the position of the detector is determined by using the relation chart established in the step S24.

In the above embodiment, the rise time of the output signal S ₁(t)、S₂ (t) is calculated for extracting the time constants τ ₁ and τ ₂, and then position recognition is performed using τ ₁ and τ ₂. Determining the range of the ratio T of different detector positions through a plurality of tests based on the rising time of signals output from two ends of the two charge sensitive amplifiers, wherein T is the ratio of the rising time of a single read-out signal to the total rising time of the two read-out signals; the position of the detector is then determined by the relation between the measured ratio T and the previously determined detector position and the ratio T.

S31, in the step S22, in the obtained energy peak diagram, the actual test energy E _pi is obtained, the standard energy of each radioactive source is different from the standard energy of the radioactive source with different E _r, the standard energy of the same radioactive source is the same, and the corresponding actual test energy E _p is recorded;

S32, obtaining a correction coefficient K _i and an offset a _i, performing linear regression on each position i by using standard energy E _r and actual test energy E _pi, obtaining a correction coefficient K _i and an offset a _i, matching a relation chart established in the step S24, and establishing a corresponding correction relation chart; matching the measured ratio F with a pre-established relation chart to find the nearest position i;

and S33, compensation calculation, namely performing accurate correction:

E_r＝K_i·E_pi+a_i (7)

The corrected energy E is equal to the standard energy E _r.

In the above embodiment, the nuclear radiation detector shares two charge sensitive amplifiers for signal readout, and the amount of charge generated by the nuclear radiation detector is partially dissipated in the series resistor network during the shunt process, so that the total amplitude of the readout signals of the two charge sensitive amplifiers becomes smaller, which is no longer proportional to the energy deposition size in the detector, that is, the total amount of charge generated by the detector. The position of the nuclear radiation detector is thus identified from the ratios F and T, and the total amplitude of its read-out signal is then corrected according to the position of the detector, so that the amount of energy deposition in the detector is proportional to the total amplitude of the read-out signal.

Compared with the prior art, the invention has the following beneficial effects:

Compared with the traditional multichannel read-out electronics, the invention greatly reduces the number of electronic channels, only comprises 2 electronic channels, has better signal-to-noise ratio and reduces the power consumption of electronics. The charge signals generated by the n detectors are split into 2 charge signals through resistors to be output, and the serial readout circuit is simple in structure. The signal is divided into 2 parts only, so that the amplitude of the extracted signal is large, the noise is small, and the corresponding channels of the nuclear radiation detector are accurately distinguished by analyzing the pulse amplitude of the double-end reading circuit, counting the energy resolution and responding to the specific positions of the detector. Meanwhile, the operation amount of the circuit is reduced, the power consumption and the area of related circuits are reduced, and the volume and the weight of the low-energy imaging device are also reduced.

Compared with other existing read-out circuit channels, the invention greatly reduces the number of electronic read-out channels, ensures better signal-to-noise ratio and realizes accurate positioning of a plurality of detector positions. Meanwhile, the scale of the circuit is reduced, the power consumption and the area of the related circuit are reduced, and the volume and the weight of the low-energy imaging device are also reduced, so that the system is simple in structure and convenient to build, the accurate positioning of the position can be realized at low cost, and the development of the portable ray imaging device is facilitated.

Drawings

Fig. 1 is a schematic diagram of a series readout circuit direct coupling implementation of a nuclear radiation detector according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of an implementation principle of ac coupling of a series readout circuit of a nuclear radiation detector according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a method for identifying a position of a series readout circuit of a nuclear radiation detector according to an embodiment of the present invention.

Fig. 4 is a flow chart of an amplitude ratio method of a position identification method of a series readout circuit of a nuclear radiation detector according to an embodiment of the present invention.

Fig. 5 is a flow chart of a method for identifying a rising time ratio of a position of a series readout circuit of a nuclear radiation detector according to an embodiment of the present invention.

Fig. 6 is a chart of the position spectra of 16 detectors of ¹³⁷ Cs radioactive sources provided by an embodiment of the present invention.

Fig. 7 is a graph of the positional scatter relationship of 16 detectors according to an embodiment of the present invention.

Fig. 8 is a diagram of 16 detector energy calibration prior to the provision of an embodiment of the present invention.

Fig. 9 is a graph of 16 corrected detector energies according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail with reference to the following examples and drawings, but it should be understood that the examples and drawings are only for illustrative purposes and are not intended to limit the scope of the present invention in any way. All reasonable variations and combinations that are included within the scope of the inventive concept fall within the scope of the present invention.

The invention is further described below with reference to the accompanying drawings.

For multi-channel electronic processing, if each signal is read out one by one for processing, each complete information is obtained, and further positioning is more accurate, but the signal reading circuit part is very huge, and the corresponding back-end signal processing is very difficult, for example, imaging needs to process a large number of channels, and a huge and complex electronic acquisition system is difficult to realize, and even if the system can be realized, the cost is very high. Therefore, it is necessary to study how to effectively simplify the multi-output signal readout circuit. The invention innovatively proposes a series readout circuit of nuclear radiation detectors.

The invention provides a series read-out circuit of a nuclear radiation detector, which is hereinafter referred to as a series read-out circuit, and the structure of the series read-out circuit comprises two charge sensitive preamplifiers positioned at two ends and a series shunt resistance network between the two charge sensitive preamplifiers; specifically, it includes 2 charge-sensitive preamplifiers, n (n is a natural number greater than 2) detectors for nuclear radiation detection, and n-1 shunt resistors R. The charge sensitive preamplifier is composed of an operational amplifier G ₁、G₂, a feedback capacitor C _f and a feedback resistor R _f. A is the amplification factor of the operational amplifier, and C _f and R _f are connected in parallel to the negative input and output ends of the operational amplifier; time constant τ=r _f·C_f. The output amplitude of the charge sensitive preamplifier reflects the magnitude of the input charge and is independent of the input capacitance, thus having good low noise performance, and the output signal amplitude is substantially unaffected by the inter-detector capacitance. The detector may be directly connected to the shunt resistor by a wire or may be ac coupled to the shunt resistor by a capacitor. And then the detector is connected to two charge sensitive preamplifiers in series through a wire to realize the split-flow reading S ₁(t)、S₂ (t) of the charge signals generated by the detector. The series readout circuit reduces the number of channels of readout electronics and ensures better charge collection, thereby improving the signal-to-noise ratio of the readout signal.

Example 1

As shown in fig. 1, both ends of the series shunt resistor network are connected to the operational amplifiers G ₁、G₂ of the 2 charge-sensitive preamplifiers through corresponding common lines. Specifically, the operational amplifier G1 at the left end outputs toward the left end, the operational amplifier G ₂ at the right end outputs toward the right end, the negative input end and the output end of each operational amplifier are connected in parallel with the feedback capacitor C _f and the feedback resistor R _f, and the positive input end of each operational amplifier is grounded.

The detector may be directly connected to the shunt resistor by a wire or may be ac coupled to the shunt resistor by a capacitor. And then the detector is connected to two charge sensitive preamplifiers in series through a wire to realize the split-flow reading S ₁(t)、S₂ (t) of the charge signals generated by the detector. The charge signal generated by the detector is split into two-end signal output through a resistor network connected in series, the two-end reading circuit is shared, and the number of electronic reading channels is saved. The access mode of the detector comprises direct coupling (shown in figure 1) and alternating coupling (shown in figure 2); the direct coupling is to directly connect the pulse signal output by the detector to the input end of the operational amplifier. The AC coupling is to reduce the DC offset of the detector output and to connect the input end of the operational amplifier through the capacitor. The detector may be directly connected to the shunt resistor by a wire or may be ac coupled to the shunt resistor by a capacitor.

And a shunt resistor is arranged between the ports of every two adjacent detectors connected to the common line, and the total number of the shunt resistors is n-1. The two ends of the common line amplify the collected signals through the charge pre-sensitive amplifier.

The signal amplitude of the output signal S ₁(t)、S₂ (t) is calculated for extracting the amplification factor a ₁、A₂, and then position recognition is performed using a ₁、A₂. Determining a ratio F range of different detector positions through a plurality of tests based on the magnitudes of the output signals of the two charge-sensitive preamplifiers, wherein F is the ratio of the amplitude of a single read-out signal to the total amplitude of the two read-out signals; the position of the detector is then determined by measuring the relation of the ratio F to the detector position determined in advance to the ratio F.

The rise time of the output signal S ₁(t)、S₂ (t) is calculated for extracting the time constant τ ₁、τ₂, and then position recognition is performed using τ ₁、τ₂. Determining a ratio T range of different detector positions through a plurality of tests based on the magnitudes of the output signals of the two charge-sensitive preamplifiers, wherein T is the ratio of the rise time of a single read-out signal to the total rise time of the two read-out signals; the position of the detector is then determined by measuring the ratio T in relation to the detector position determined in advance in relation to the ratio T.

The series readout circuit of the nuclear radiation detector is used as a nuclear radiation identification circuit, so that the nuclear radiation position of the region to be detected can be accurately identified, as shown in fig. 3, the identification principle is based on the output signals of the charge sensitive preamplifiers at two ends output by the series readout circuit of the nuclear radiation detector, which are S ₁(t)、S₂ (t), respectively, and the pulse signal amplitudes output by the charge sensitive preamplifiers at two ends are different due to the response generated by the detectors at different positions, so that the accurate positioning can be performed through the ratio of the signals at two ends.

Specifically, a plurality of detectors detect nuclear pulse signals generated by the radioactive source, a processor reads rising time, and the detected output signals S ₁(t)、S₂ (t) are used for detecting the ratio of the series shunt resistor network at each position in a large quantity based on the sizes of the output signals at two ends;

The processor calculates the ratio of a large number of output signals and the corresponding series shunt resistor network range to compare to obtain specific acquisition positions of the signals, and the relation between the rising time and the detector response S ₁(t)、S₂ (t) is expressed as the following formula (1) and formula (2):

Where B ₁、B₂ is a constant, A ₁、A₂ is the amplification factor of the operational amplifier, and the B ₁、B₂ constant is determined by the parameters of the detector.

When R ₁＝R₂＝R₃＝R₄……＝R_n-1＝R_i, the time constants τ1, τ2 of the kth detector are derived from equations (3) and (4), respectively:

τ₁＝R_f·C_f·(k-1) (3)

τ₂＝R_f·C_f·(n-k) (4)

In addition, the resistance value of the R ₁、R₂、……R_n-2、R_n-1 internal resistance sequence can be adjusted to modify the change trend of the nuclear pulse signal.

As another embodiment, the processor may also obtain a specific acquisition position of each signal by comparing the ratio of the amplification coefficients with the corresponding range of the series shunt resistor network, specifically, the ratio of the amplification coefficients is F, the ratio of the time constants is T, and the relationship between them is expressed as formula (5) and formula (6):

Wherein F is the ratio of the single-ended nuclear pulse signal amplitude to the total nuclear pulse signal amplitude at both ends, and T is the ratio of the rising time of the single-ended nuclear pulse signal to the rising time of the total nuclear pulse signal at both ends. The value ranges of F and T are all 0-1, and the value ranges are divided into m sections, and the value of the section where the ratio falls is the value of the section.

The k constant is selected according to different detectors, the F value range is 0-1, the range is divided into m sections, and then the specific detector response determination position can be obtained by measuring and calculating the relation between the ratio T of 2 charge sensitive preamplifier output signals and the detector position and the ratio T which are obtained in advance. The interval in which the ratio falls is the location of which value. The sizes of the data of the two-end test output signals received by the processor are in a ratio, and the data is accurately positioned according to the ratio.

According to the above identification principle, the present embodiment also provides a method for identifying the position of the series readout circuit of the nuclear radiation detector, which is used for determining the detector position. The identification method involves two main techniques: the amplitude ratio method and the rise time ratio method respectively comprise the following steps:

S0, assembling a series readout circuit, wherein two charge sensitive preamplifiers are respectively arranged at two ends of a shared line of an assembled series shunt resistor network, and the power supply of the two charge sensitive preamplifiers is selected to be double-power supply or single-power supply in the embodiment;

a positive power supply (+v) is connected to the positive power supply input of the circuit. A negative supply (-V) is connected to the negative supply input of the circuit. The Ground (GND) is connected to the ground terminal of the circuit.

The positive and negative power supply voltages are set to the desired values but the power supply is not turned on. The current limit of the power supply is set to prevent overcurrent.

The positive power supply (+V) is turned on first, and the current and voltage are observed to ensure the normal state. The negative power (-V) was turned on again, and the current and voltage were also observed. The voltage at each key point of the circuit is measured by using a universal meter, and the voltage is ensured to be in a normal range. Checking the working state of the circuit to confirm that no abnormal condition exists.

And the power supply voltage is regulated according to the requirement, necessary debugging and calibration are carried out, and the normal operation of the circuit is ensured. Ensure that the power line and the ground line have no short circuit phenomenon. The circuit temperature is monitored after power-up to prevent overheating.

Through the steps, the safe and reliable power-on of the dual-power supply circuit is ensured, and the dual-power supply circuit can work normally. If a problem is encountered in the power-on process, the power is timely cut off, the circuit is checked, and necessary adjustment and repair are carried out. Then, position identification is carried out according to an amplitude ratio method or a rise time ratio method, and in the aspect of power supply of the two charge sensitive preamplifiers, the amplitude ratio method selects dual-power supply or single-power supply, the rise time ratio method selects dual-power supply, and the two methods specifically comprise the following steps:

1. Amplitude ratio method

As in fig. 4, S11: detection output signals S ₁ (t) and S ₂ (t): the two charge-sensitive preamplifiers output signals are detected, which are representative of the response across the detector, and the two charge-sensitive preamplifiers output signals S ₁(t)、S₂ (t) respectively. To reduce the noise effect, both signals are filtered.

S12, calculating the amplitude of an output signal S ₁(t)、S₂ (t), wherein the amplitude is used for extracting amplification coefficients which are respectively marked as A ₁ and A ₂, and the calculation formula is as follows:

S13, calculating a ratio F of the single read nuclear pulse signal amplitude to the total amplitude of the two read total nuclear pulse signals according to the formula, wherein the calculation formula is as follows:

S14, determining the relation between the ratio F and the position: and (3) changing different detection positions of the detector, determining the range of the ratio F corresponding to the different detector positions through a large number of tests, and establishing a relation chart of the detector positions and the ratio F. These relationship chart ratios were obtained by simulation and extensive experimentation at known locations.

S15, determining the position of a detector: the currently measured ratios F and T are matched to the ratios corresponding to the known positions using a pre-established relationship chart. The closest pair of ratios is found to determine the position of the detector. In the formal measurement, the ratio F of the current signal is measured by executing S11-S13, and the position of the detector is determined by using the relation chart established in the step S14.

2. Rise time ratio method

As shown in fig. 5, S21: detection output signal S ₁(t)、S₂ (t): the two charge-sensitive preamplifiers output signals S ₁(t)、S₂ (t), respectively.

S22, extracting rising time tau ₁ and tau ₂: the rise times τ ₁ and τ ₂ can be directly read out by measuring the time period from the baseline to the peak of the signal and directly displayed on an oscilloscope, or can be calculated by calculating the rise time of the output signal S ₁(t)、S₂ (t), and the rise time is respectively recorded as τ ₁ and τ ₂, and the calculation formula is as follows:

τ₁＝R_f·C_f·(k-1) (3)

τ₂＝R_f·C_f·(n-k) (4)

S23, ratio T: calculating the ratio T of the rising time of a single read signal to the total rising time of two read signals, wherein the calculation formula is as follows:

S24, determining the relation between the ratio T and the position: and changing the detection positions of different detectors, determining the range of the ratio T corresponding to the positions of the different detectors through a large number of tests, and establishing a relation chart of the positions of the detectors and the ratio T. The ratios of these relationship charts were obtained by simulation and extensive experimentation at known locations.

S25, determining the position of a detector: the ratio T currently measured is matched to the ratio corresponding to the known position using a pre-established relationship chart. The closest pair of ratios is found to determine the position of the detector. In the formal measurement, the ratio T of the current signal is measured by executing S21-S23, and the position of the detector is determined by utilizing the relation chart established in the step S24.

By the amplitude ratio method and the rise time ratio method, accurate measurement of the detector position and the deposition energy can be realized. The amplitude ratio method mainly uses the ratio of signal amplitudes, while the rise time ratio method uses the ratio of signal rise times. Both of these methods can provide more accurate positioning.

After the position of the nuclear radiation detector is identified according to the ratio F and T in the embodiment, the total amplitude of the read signal is corrected according to the position of the detector, so that the energy deposition in the detector is in direct proportion to the total amplitude of the read signal.

In practical applications, the current signal amplification is measured as or rise times τ ₁ and τ ₂. The ratio F and T of the current signal is calculated. Establishing a relation chart: the relationship chart ratio is obtained through simulation and a plurality of experiments by using the pre-known position. The matching relation chart matches the currently measured ratios F and T with the ratios corresponding to the known positions. The position is determined to find the closest ratio to determine the position of the detector.

By the above steps, the position of the detector can be accurately determined based on the ratio of the signal amplitude and the rise time.

Example 2

Because the nuclear radiation detector shares two charge sensitive amplifiers for signal readout, the charge quantity generated by the nuclear radiation detector is partially dissipated in a series resistor network in the process of shunt, so that the total amplitude of the readout signals of the two charge sensitive amplifiers becomes smaller, and the total amplitude is not proportional to the energy deposition size in the detector, namely the total charge quantity generated by the detector. Thus, the signal can be corrected.

The position of the nuclear radiation detector is identified by the ratio F or T, and then the total amplitude of the read-out signal is corrected according to the position of the detector, so that the energy deposition in the detector is in direct proportion to the total amplitude of the read-out signal.

At each known location, signal amplitudes A ₁ and A ₂ are recorded, and the ratio F or T is calculated, along with the corresponding correction factor K for the actual energy deposition. New calibration data is added to the relationship chart to ensure that the correction factor K corresponding to the ratio F or T is up to date.

The correction formula is as follows:

E_r＝K_i·E_pi+a_i (7)

Where i is the reference number of the different positions, E _r is the standard energy, and is a constant value, the standard energies of different radioactive sources are different, but the standard energies of the same radioactive source are the same. E _pi is the actual test energy. K _i and a _i are correction coefficients and offsets, which are related to position i.

E _r is the standard energy, E _pi is the actual test energy, and K _i and a _i are obtained by mass test. The actual test energy is calibrated to be equal to the standard value with the known position.

Therefore, the position identifying method of the serial readout circuit of the nuclear radiation detector provided in the present embodiment further includes the following correction step S3, specifically as follows:

S31, in the step S12 or S23, in the obtained energy peak diagram, obtaining actual test energy E _pi, wherein the standard energy of each radioactive source is the same as the standard energy of the same radioactive source with different energy of E _r, and recording corresponding actual test energy E _p;

S32, obtaining a correction coefficient K _i and an offset a _i:

Performing linear regression on each position i by using standard energy E _r and actual test energy E _pi, solving a correction coefficient K _i and an offset a _i, matching the relation chart established in the step S14 or S23, and establishing a corresponding correction relation chart; the measured ratio F or T is matched with a pre-established relationship chart to find the closest position i.

And S33, compensation calculation, namely performing accurate correction:

Applying a correction formula, and correcting the actual test energy E _pi by using the corresponding correction coefficient K _i and the offset a _i according to the matched position i of S32:

E_r＝K_i·E_pi+a_i (7)

The corrected energy E should be equal to the standard energy E _r. And carrying out real-time compensation on the energy spectrum through a large number of tests of known positions, and realizing accurate correction of the energy spectrum.

The magnitude of the energy deposition in the detector is made proportional to the total amplitude of the read signal.

Example 3

In this embodiment, a detector array is formed by a4×4 SIPM array, a series readout circuit of nuclear radiation detectors is formed, and a position recognition experiment and a correction experiment are performed.

First, the series readout circuit is assembled:

1. A4 x4 SIPM array is assembled, and 16 experiments adopt SIPM of the model EQR 1511-6060D-S. 15 30Ω resistors (R ₁-R₁₅) are connected in series.

2. Two LT6236 charge-sensitive preamplifiers (G1 and G2) are connected. The negative input end and the output end of the amplifier are connected in parallel with a feedback capacitor C _f =1 nF and a feedback resistor R _f =50 kΩ, and the positive input end is grounded.

3. A +38v bias voltage is provided to the SIPM array and a 3.3V voltage is provided to the LT6236 op-amp.

4. ¹³⁷ Cs rays strike a scintillator (CsI) to generate photons which enter the SIPM array and output weak current pulse signals.

Next, the signals are connected to the shunt resistor through a wire, and the signals S1 (t) and S2 (t) are read out.

5. The read signal pulse waveform amplitudes, noted as a ₁ and a ₂, were acquired using a high-speed ADC. The pulse amplitude data at the left and right ends are processed by MATLAB, and a two-dimensional scatter diagram (shown in figure 7) and a spectrum diagram of 16 detector positions (shown in figure 6) are drawn according to a formula 5 for calculating F. The scatter plot shows the relative position of the detector in physical space and the signal response relationship. The line graph shows the signal count rate distribution of 16 SIPM detectors for localization and analysis.

6. The actual measured energy E _pi for each detector was obtained in the energy spectrum, and the standard energy E _r(¹³⁷ Cs was recorded as 662 keV). The actual measured energy is corrected in MATLAB using correction formula E _r＝K_i·E_pi+a_i to make the corrected energy equal to the standard energy, as shown in fig. 8 and 9.

The above examples are only preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the concept of the invention belong to the protection scope of the invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.

Claims

1. A series readout circuit of nuclear radiation detectors, characterized by: the charge-sensitive preamplifier comprises a series shunt resistor network, charge-sensitive preamplifiers and a common line, wherein the charge-sensitive preamplifiers are positioned at two ends of the series shunt resistor network; the series shunt resistor network comprises n detectors connected to the common line, wherein the detectors are used for nuclear radiation detection, and n is a natural number greater than 2; a shunt resistor R is arranged between every two adjacent access points of the detectors connected to the common line, and the number of the shunt resistors R is n-1; the single charge sensitive preamplifier comprises an operational amplifier G, a feedback capacitor C _f, a feedback resistor R _f,C_f and a feedback resistor R _f which are connected in parallel with negative input and output ends of the operational amplifier G, and the two operational amplifiers are G ₁ and G ₂ respectively.

2. The series readout circuit of nuclear radiation detectors of claim 1, wherein: and an alternating current coupling capacitor C is also connected before the detector is connected to the common line.

3. A method of position identification of a series readout circuit of a nuclear radiation detector as claimed in any one of claims 1 to 2, characterized in that: the method sequentially comprises the following steps of:

wherein B ₁、B₂ is a constant, A ₁、A₂ is an amplification factor, and B ₁、B₂ constant is determined by parameters of the detector; i is the serial number of a specific shunt resistor;

4. A method of location identification as claimed in claim 3, wherein: the method also comprises a correction step S3, which is specifically as follows:

S31, according to the step S12, obtaining actual test energy E _pi in the obtained spectrogram, wherein the standard energy of each radioactive source is different from E _r, the standard energy of the same radioactive source is different from the standard energy of the same radioactive source, and recording corresponding actual test energy E _p;

and S33, compensation calculation, namely performing accurate correction:

E_r＝K_i·E_pi+a_i (7)

The corrected energy E is equal to the standard energy E _r.

5. A method of position identification of a series readout circuit of a nuclear radiation detector as claimed in any one of claims 1 to 2, characterized in that: the method sequentially comprises the following steps of:

S23, ratio T: the ratio T of the single read signal rise time to the total rise time of the two read signals is calculated as follows:

6. The location identification method of claim 5, wherein: the method also comprises a correction step S3, which is specifically as follows:

S31, according to the step S22, obtaining actual test energy E _pi in the obtained energy peak diagram, wherein the standard energy of each radioactive source is the same as the standard energy of the same radioactive source with different energy of E _r, and recording corresponding actual test energy E _p;

and S33, compensation calculation, namely performing accurate correction:

E_r＝K_i·E_pi+a_i (7)

The corrected energy E is equal to the standard energy E _r.