Alpha and beta particle discrimination method and system based on liquid scintillation counter

Abstract

The embodiment of the invention discloses an alpha and beta particle discrimination method and system based on a liquid scintillation counter. The system comprises a signal detection module used for detecting alpha and beta particle electric signals; the signal shaping circuit module is connected with the signal detection module and is used for shaping the detected alpha and beta particle electric signals; a peak holding circuit module; the peak holding module is connected with the signal shaping circuit module and is used for carrying out amplification peak holding processing on the shaped alpha and beta particle electric signals; a signal discrimination circuit module; the signal processing circuit module is respectively connected with the signal shaping circuit module and the peak holding circuit module and is used for identifying electric signals useful for alpha and beta particles; an FPGA data processing module; and the signal discriminating circuit module is connected with the signal discriminating circuit module and is used for discriminating the square wave signals corresponding to the alpha particles and the beta particles.

Description

Technical Field

[0001] This invention belongs to the field of radioactive particle detection technology, specifically relating to a method and system for distinguishing α and β particles based on a liquid scintillation counter. Background Technology

[0002] Liquid scintillation (LSC, or liquid scintillation counting technology) has demonstrated great convenience and practicality in measuring alpha and beta radioactive particles due to its rapid and efficient measurement process and simple sample preparation method. It can be applied to many fields such as environmental monitoring, nuclear medicine, radiopharmaceutical development, nuclear material identification, geological exploration, and radiochemical research.

[0003] When measuring a mixture of α and β particles using a liquid scintillation counter, β particles produce a continuous energy spectrum from 0 to a maximum energy of 2 MeV, while α particles emit high-energy particles from 4 MeV to 6 MeV. Compared to β particles, the interaction between α particles and the liquid scintillation medium is characterized by a lower scintillation or photon yield, with light output approximately one-tenth that of β particles. This leads to potential energy overlap between some α and β nuclides, and the energy spectra cannot be distinguished by simple energy resolution, making it impossible to differentiate between α and β particles and to count α and β particles separately in a mixed α and β sample.

[0004] Currently, the α and β discrimination functions of commercial liquid scintillators primarily rely on the differences in decay time of fluorescence generated by different rays, i.e., differences in pulse shape, to achieve differentiation between rays. However, capturing nanosecond-level pulse shape differences requires extremely fast electronic systems; the sampling rate of the ADC typically needs to reach hundreds of MS / s or even GS / s. Moreover, to accurately analyze the pulse shape, the ADC needs sufficient resolution to distinguish subtle current / voltage differences. Therefore, the analog circuitry is complex, difficult to debug, and costly. Summary of the Invention

[0005] In view of this, in order to overcome the problems of high circuit complexity, difficult debugging and high cost of the existing α and β particle counting methods based on liquid scintillation counters, some embodiments disclose α and β particle discrimination methods and discrimination systems based on liquid scintillation counters.

[0006] Some embodiments disclose an alpha and beta particle discrimination system based on a liquid scintillation counter, including:

[0007] The signal detection module is used to detect the electrical signals of alpha and beta particles;

[0008] The signal shaping circuit module is connected to the signal detection module and is used to shape the detected α and β particle electrical signals.

[0009] Peak hold circuit module; configured to connect to the signal shaping circuit module, used to amplify and hold the peak value of the shaped α and β particle electrical signals;

[0010] Signal discrimination circuit module; configured to be connected to the signal shaping circuit module and the peak hold circuit module respectively, used to discriminate electrical signals useful for alpha and beta particles;

[0011] FPGA data processing module; configured to connect with the signal discrimination circuit module to distinguish the square wave signals corresponding to α and β particles.

[0012] Furthermore, in some embodiments of the α / β particle discrimination system based on a liquid scintillation counter, the signal shaping circuit module includes:

[0013] Operational amplifier U3; the non-inverting input terminal of operational amplifier U3 is configured as an electrical signal input terminal, and a resistor R16 and a capacitor C13 are connected in parallel between the inverting input terminal and the output terminal of operational amplifier U3; the output terminal of operational amplifier U3 is further provided with a series resistor R10 and a resistor R11 in sequence.

[0014] Analog multiplexer U6; The S1, S2, S3, S4, and S5 ports of analog multiplexer U6 are respectively connected to resistors R20, R21, R19, R24, and UR2. Resistors R20, R21, R19, R24, and UR2 are further connected together between resistors R10 and R11.

[0015] Operational amplifier U5; a resistor R7 is connected to the non-inverting input of operational amplifier U5, and resistor R7 is further grounded; a resistor R11 is connected to the inverting input of operational amplifier U5; a resistor R15 and a capacitor C11 are connected in parallel between the inverting input and the output of operational amplifier U5; the inverting input of operational amplifier U5 is also connected to the D interface of an analog multiplexer.

[0016] Some embodiments disclose an alpha / beta particle discrimination system based on a liquid scintillation counter, wherein the peak hold circuit module includes:

[0017] Operational amplifier U8; a resistor R17 is connected to the non-inverting input of operational amplifier U8, and resistor R17 is further connected to the signal output of the signal shaping module; a capacitor C21 and a resistor R30 are connected in series between the inverting input and the output of operational amplifier U8; a diode D2 is also connected in parallel between the inverting input and the output of operational amplifier U8.

[0018] Operational amplifier U7; Resistor R22 is connected to the inverting input terminal of operational amplifier U7, and resistor R22 is further connected to the output terminal of operational amplifier U7; Resistor R27 is connected to the non-inverting input terminal of operational amplifier U7, and resistor R27 is further connected to resistors R28 and R29. Resistor R28 is connected to capacitor C16, and resistor R29 is connected to capacitor C18. Capacitors C16 and C18 are further connected to each other and grounded.

[0019] The output terminal of operational amplifier U8 is further connected to diode D1, and diode D1 is further connected to the connection point of resistors R27, R28, and R29; the inverting input terminal of operational amplifier U8 is further connected to the connection point of diode D1 and resistors R27, R28, and R29; the connection point between the inverting input terminal of operational amplifier U8 and diode D1 is further connected to resistor R26, and resistor R26 is further connected to the output terminal of operational amplifier U7.

[0020] The connection point between resistor R22 and the output terminal of operational amplifier U7 is further connected to resistor R23, and resistor R23 is further connected to resistor UR1. The other end of resistor UR1 is grounded, and the movable end of resistor UR1 is set as the signal output terminal of the peak hold circuit module.

[0021] Some embodiments disclose an alpha and beta particle discrimination system based on a liquid scintillation counter, wherein the signal discrimination circuit module includes:

[0022] High-speed differential comparator U4; The non-inverting input of high-speed differential comparator U4 is connected to resistors R8 and R13 in sequence, with resistor R13 grounded. The connection point between resistors R8 and R13 is configured as the first signal input terminal, used to input the electrical signal output by the signal shaping circuit module; The inverting input of high-speed differential comparator U4 is connected to resistor R12 and capacitor C9 in sequence, with capacitor C9 further grounded. The connection point between resistor R12 and capacitor C9 is configured as the second signal input terminal, used to input the electrical signal output by the peak hold circuit module;

[0023] The output terminal of the high-speed differential comparator U4 is connected to a resistor R9. Resistor R9 is further connected to one end of a parallel resistor R14 and a capacitor C10. The other end of the parallel resistor R14 and capacitor C10 is grounded. The connection point between resistor R9 and resistor R14 and capacitor C10 is set as the output terminal, which outputs a square wave signal.

[0024] On the other hand, some embodiments disclose α and β particle discrimination methods based on liquid scintillation counters, implemented by the α and β particle discrimination system based on liquid scintillation counters disclosed in the embodiments of the present invention. The method includes:

[0025] Detecting electrical signals from alpha and beta particles;

[0026] The detected electrical signals of α and β particles are shaped;

[0027] The shaped electrical signal is then subjected to peak amplification and hold processing.

[0028] Filter out noise and identify useful signals;

[0029] The useful signals identified are processed to count α and β particles separately.

[0030] Furthermore, some embodiments disclose an α and β particle discrimination method based on a liquid scintillation counter, in which the useful signal is a square wave signal, and the pulse width of the waveform signal is used to distinguish α and β particles.

[0031] Some embodiments of the alpha and beta particle discrimination method based on a liquid scintillation counter disclose data processing of the useful signals to be discerned, including:

[0032] By adjusting the discrimination threshold of the FPGA, the relationship between the crosstalk ratio of α-rays to β-channels and the crosstalk ratio of β-rays to α-channels under different α and β discrimination thresholds was obtained; among them,

[0033] Method for calculating the cross-channel ratio of α-rays to β-channels:

[0034]

[0035] Method for calculating the cross-channel ratio of β-rays to α-channel:

[0036]

[0037] In the formula, n β,avg n is the average count within channel β; α,avg The average count within channel α.

[0038] The α and β particle discrimination method and system based on a liquid scintillation counter disclosed in this invention features a discrimination circuit designed based on a constant-time ratio method, achieving α and β particle discrimination and counting with a false discrimination rate of less than 3%. The discrimination and counting of α and β particles are implemented directly in pure hardware, with response speed limited only by comparator and switching delays, resulting in a total time of <50ns. No high-speed ADC is required, significantly reducing power consumption and cost. Dual capacitor holding allows for independent measurement of wide and narrow pulse energy, facilitating subsequent counting, waveform reconstruction, or closed-loop control. The threshold, gain, and low-pass cutoff frequency can all be adjusted via resistors and capacitors to adapt to different width threshold values. Attached Figure Description

[0039] Figure 1 , OneSome embodiments disclose schematic diagrams of the composition of α and β particle discrimination systems based on liquid scintillation counters;

[0040] Figure 2 , One Some embodiments disclose schematic diagrams of the signal shaping circuit module structure;

[0041] Figure 3 , One Some embodiments disclose a schematic diagram of the peak hold circuit module structure;

[0042] Figure 4 , One Some embodiments disclose schematic diagrams of the signal discrimination circuit module structure;

[0043] Figure 5 , One Some embodiments disclose a schematic diagram of direct pulse counting;

[0044] Figure 6 , One The discrimination and counting results curves disclosed in some embodiments.

[0045] Figure Labels

[0046] Detailed Implementation

[0047] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in these embodiments of the invention, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in these embodiments is merely for describing particular implementations and is not intended to limit the scope of the disclosure of these embodiments.

[0048] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of this invention pertain; other experimental methods and technical means not specifically noted in the embodiments of this invention refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0049] The terms “basic” and “approximately” as used herein are used to describe small fluctuations. For example, they can mean less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or expressed in range format herein are used for convenience and brevity only, and should therefore be interpreted flexibly to include not only the explicitly listed values ​​that define the range, but also all independent values ​​or subranges contained within that range. For example, a numerical range of “1–5%” should be interpreted to include not only the explicitly listed values ​​from 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, this numerical range includes independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1%–3%, 2%–4%, and 3%–5%, etc. This principle also applies to ranges that list only one value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0050] In this document, including in the claims, conjunctions such as "comprising," "including," "with," "having," "containing," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the conjunctions "consisting of" and "composed of" are closed conjunctions.

[0051] To better illustrate the content of this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the invention can be practiced even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail, in order to highlight the main points of the invention.

[0052] Without conflict, the technical features disclosed in the embodiments of the present invention can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of the present invention.

[0053] Generally, under the same pulse peak energy, it is difficult to clearly distinguish the pulse signals generated by alpha and beta particles through a scintillator based on amplitude alone. However, due to the different pulse decay delays produced by alpha and beta particles, this difference in pulse decay delay can be used to differentiate between alpha and beta rays. Typically, after a radioactive particle excites some scintillator molecules, the scintillator molecules will enter two excited states: a singlet state (the instantaneous decay portion) and a triplet state (the delayed decay portion). The more alpha particles are ionized, the more conducive it is to the formation of the triplet state, i.e., the greater the delayed decay portion. In scintillating fluids, the instantaneous decay time is usually less than 20 ns, while the delayed decay time is usually less than 100 ns. Beta particles have more instantaneous components, while alpha particles have more delayed components. Because alpha particles have more delayed components, the pulse shape includes both instantaneous and delayed decay parts, so the pulse generated by alpha particles is considered "wider" than that generated by beta particles.

[0054] The α / β particle discrimination method based on a liquid scintillation counter provided in this invention uses an RC integrator circuit for preprocessing to minimize mutual interference between α and β particles during measurement. Assuming input pulses with the same amplitude but different widths, the relationship between input and output voltage is: a wider output pulse width corresponds to a longer charging time and a higher output pulse amplitude; conversely, a narrower input pulse width corresponds to a shorter charging time and a lower output pulse amplitude. The integrator circuit can significantly distinguish the α / β signals for subsequent processing.

[0055] The integrated pulse signal is split into two paths. One path passes through a voltage divider to adjust the pulse height, and then a pulse peak hold circuit automatically latches the peak value of the output signal. A TTL comparator records the pulse width information and outputs the corresponding square wave signal. Since the α and β pulse signals have significantly different widths, the FPGA can use a simple counting method to measure the pulse width. The discrimination time threshold (t) is adjusted to distinguish between α and β pulse signals; β counters count signals smaller than the set threshold t1, and α counters count signals larger than the threshold t2.

[0056] Some embodiments disclose alpha and beta particle discrimination systems based on liquid scintillation counters, such as Figure 1 As shown, it includes:

[0057] The signal detection module is used to detect the electrical signals of alpha and beta particles;

[0058] The signal shaping circuit module is connected to the signal detection module and is used to shape the detected α and β particle electrical signals.

[0059] Peak hold circuit module; configured to connect to the signal shaping circuit module, used to amplify and hold the peak value of the shaped α and β particle electrical signals;

[0060] Signal discrimination circuit module; configured to be connected to the signal shaping circuit module and the peak hold circuit module respectively, used to discriminate electrical signals useful for alpha and beta particles;

[0061] FPGA data processing module; configured to connect with the signal discrimination circuit module to distinguish the electrical signals corresponding to α and β particles.

[0062] Some embodiments disclose an alpha and beta particle discrimination system based on a liquid scintillation counter. The signal detection module includes detectors, which are three-channel photomultiplier tubes (PMTs) installed in a lead chamber. To eliminate the influence of abnormal signals, the raw signal is recorded using a coincidence counting method. A signal is considered valid when read by at least two detectors, and is then stored and processed.

[0063] Some embodiments disclose alpha and beta particle discrimination systems based on liquid scintillation counters, such as Figure 2 As shown, the signal shaping circuit module includes:

[0064] Operational amplifier U3; the non-inverting input terminal of operational amplifier U3 is configured as an electrical signal input terminal, and a resistor R16 and a capacitor C13 are connected in parallel between the inverting input terminal and the output terminal of operational amplifier U3; the output terminal of operational amplifier U3 is further provided with series resistors R10 and R11;

[0065] Analog multiplexer U6; The S1, S2, S3, S4, and S5 ports of analog multiplexer U6 are respectively connected to resistors R20, R21, R19, R24, and UR2. Resistors R20, R21, R19, R24, and UR2 are further connected together between resistors R10 and R11.

[0066] Operational amplifier U5; the non-inverting input terminal of operational amplifier U5 is connected to resistor R7, which is further grounded; the inverting input terminal of operational amplifier U5 is connected to resistor R11; a resistor R15 and a capacitor C11 connected in parallel are provided between the inverting input terminal and the output terminal of operational amplifier U5; the inverting input terminal of operational amplifier U5 is also connected to the D interface terminal of the analog multiplexer.

[0067] Typically, the signal output from the signal detection module is first processed by the signal shaping circuit module, which performs high-impedance buffering, level conditioning, and low-impedance driving on the single-ended analog input. Then, it is passed through the 8:1 analog multiplexer U6 to achieve multi-channel selection, accurately and with low loss, sending the required analog signal to the subsequent sampling or measurement unit, thus completing the two major tasks of "analog front-end conditioning and channel multiplexing".

[0068] In some embodiments, the detector output signal of the signal detection module is a negative pulse signal at the mV level. Due to the effect of the high voltage DC blocking capacitor, the signal tail will generate a downward overshoot, becoming a bipolar signal. This can easily cause baseline shift when the count rate is relatively high. To address this, the pole-zero cancellation circuit composed of R16 and C13 is connected in parallel to the feedback loop of the operational amplifier U3 to compensate for the phase distortion of the signal during amplification, expand the bandwidth of the circuit, and enable the conditioned signal to be transmitted more accurately to the subsequent operational amplifier U5, ensuring the accuracy of the subsequent signal discrimination function. The input signal first enters through the Signal-IN port and reaches the non-inverting input of operational amplifier U3. Operational amplifier U3 forms a voltage follower to increase the input impedance and avoid signal source load effects. The output of operational amplifier U3 is then sent to the inverting input of the second-stage operational amplifier U5 via series resistors R10 and R11. Operational amplifier U5, together with capacitor C11 and resistor R15, forms a low-pass filter to filter out high-frequency noise in the signal and further shape the waveform of the gain-adjusted signal to ensure signal bandwidth and circuit stability. The output of operational amplifier U5 is connected to channel D (pin 19) of analog multiplexer U6. Typically, analog multiplexer U6 can be a DG408. The DG408 is an eight-channel single-ended analog multiplexer whose channel selection is controlled by a binary combination of 3-bit address signals MCA_A0, MCA_A1, and MCA_A2, and is also affected by MCA_EN. Enable signal control: When the enable signal is validly high, the analog multiplexer performs normal channel selection; when it is low, the analog multiplexer enters the off state, all channels are disconnected and in a high-impedance state, which can avoid invalid signals interfering with subsequent circuits and reduce the overall circuit power consumption when no signal switching is required. The control signal can precisely select the resistors R19, R20, R21, R24, and UR2 corresponding to the pins of different resistor branches S1, S2, S3, S4, and S5, respectively, and transmit them to the common output terminal D. This design allows subsequent single-channel processing circuits to process multiple signals in a time-division multiplexing manner, eliminating the need for a separate processing circuit for each signal, greatly simplifying the circuit structure and reducing hardware costs. After selection by the analog multiplexer U6, the corresponding resistor is connected to the inverting input loop of operational amplifier U5 via the output terminal D, forming a complete amplification feedback link together with the feedback resistor at the output terminal of operational amplifier U5, realizing programmable adjustment of the amplification factor.

[0069] Typically, operational amplifiers U3 and U5, as well as analog multiplexer U6, are powered by a symmetrical ±VCC / VEE power supply, with AGND providing an analog reference ground.

[0070] Some embodiments disclose alpha and beta particle discrimination systems based on liquid scintillation counters, such as Figure 3 As shown, the peak hold circuit module includes:

[0071] Operational amplifier U8; a resistor R17 is connected to the non-inverting input of operational amplifier U8, and resistor R17 is further connected to the signal output of the signal shaping module; a capacitor C21 and a resistor R30 are connected in series between the inverting input and the output of operational amplifier U8; a diode D2 is also connected in parallel between the inverting input and the output of operational amplifier U8.

[0072] Operational amplifier U7; Resistor R22 is connected to the inverting input terminal of operational amplifier U7, and resistor R22 is further connected to the output terminal of operational amplifier U7; Resistor R27 is connected to the non-inverting input terminal of operational amplifier U7, and resistor R27 is further connected to resistors R28 and R29. Resistor R28 is connected to capacitor C16, and resistor R29 is connected to capacitor C18. Capacitors C16 and C18 are further connected to each other and grounded.

[0073] The output terminal of operational amplifier U8 is further connected to diode D1, and diode D1 is further connected to the connection point of resistors R27, R28, and R29; the inverting input terminal of operational amplifier U8 is further connected to the connection point of diode D1 and resistors R27, R28, and R29; the connection point between the inverting input terminal of operational amplifier U8 and diode D1 is further connected to resistor R26, and resistor R26 is further connected to the output terminal of operational amplifier U7.

[0074] The connection point between resistor R22 and the output terminal of operational amplifier U7 is further connected to resistor R23, and resistor R23 is further connected to resistor UR1. The other end of resistor UR1 is grounded, and the movable end of resistor UR1 is set as the signal output terminal of the peak hold circuit module.

[0075] Typically, the shaped signal is split into two paths. One path enters the high-speed differential comparator U4 in the signal discrimination circuit, while the other path, after current limiting by R17, enters operational amplifiers U8 and U7 for large sum and peak hold processing. Operational amplifier U8 is the first-stage low-noise op-amp, capable of amplifying pulsed millivolt signals by 20 to 50 times and converting them to single-ended output. Capacitor C21 and resistor R30 are connected in series across the inverting input and output of U8, forming a "series RC feedback circuit" that displays bandwidth and suppresses high-frequency spikes. The series resistor R30... A DC negative feedback path is provided to stabilize the operating point of operational amplifier U8 and release the DC charge accumulated in the capacitor, ensuring long-term stable operation of the circuit and preventing signal loss due to charge accumulation. The positive terminal of D2 is connected to the inverting input terminal of operational amplifier U8, and the negative terminal is connected to the output terminal of operational amplifier U8. When the input signal causes a negative half-cycle signal at the inverting input terminal of operational amplifier U8, operational amplifier U8 will output a positive voltage. At this time, the positive terminal of diode D2 is connected to the inverting input terminal and the negative terminal is connected to the output terminal, which just meets the forward conduction condition. After diode D2 conducts, the circuit forms a deep negative feedback, and operational amplifier U8 operates in the linear region, which can accurately rectify and output the negative half-wave signal of the input. When the input signal is in the positive half-cycle, the operational amplifier U8 outputs a negative voltage, the diode D2 is reverse-biased and cut off, the feedback loop is disconnected, the operational amplifier U8 is in an open-loop state, and there is basically no corresponding signal at the output end, thus achieving precise rectification of the negative half-wave, suitable for small signal or high-precision rectification scenarios; the diode D1 acts as an amplitude threshold switch. When the signal amplitude at the inverting input of the operational amplifier U7 is lower than the conduction voltage of the diode D1, the diode D1 is cut off, and the signal cannot enter the amplification loop of U7; only when the signal amplitude exceeds the threshold, the diode D1 conducts, and the signal can be amplified by the operational amplifier U7, realizing the amplitude filtering function.

[0076] Operational amplifier U7 is the second-stage precision operational amplifier, achieving re-amplification and multi-stage low-pass filtering. Feedback resistors R27, R28, and R29, along with capacitors C16 and C18, form a third-stage low-pass filter with a cutoff frequency fc ≈ 300kHz~1MHz. Resistor R22, in conjunction with the inverting input and output of operational amplifier U7, acts as a fixed feedback resistor, providing a fundamental negative feedback path for the amplifier circuit and ensuring that operational amplifier U7 operates in the linear region. Resistor R23, connected in series with resistor UR1, is then connected in parallel with resistor R22 between the inverting input and output of operational amplifier U7. Adjusting the value of resistor UR1 changes the equivalent resistance of the feedback network, thereby adjusting the amplification factor of operational amplifier U7 and ensuring that the signal amplitude output by operational amplifier U7 matches the requirements of subsequent stages.

[0077] Operational amplifiers U7 and U8 can typically be powered by a symmetrical ±VCC / VEE power supply, with AGND providing an analog reference ground.

[0078] Some embodiments disclose alpha and beta particle discrimination systems based on liquid scintillation counters, such as Figure 4 As shown, the signal discrimination circuit module includes:

[0079] High-speed differential comparator U4; The non-inverting input of high-speed differential comparator U4 is connected to resistors R8 and R13 in sequence. Resistor R13 is grounded. The connection point between resistors R8 and R13 is set as the first signal input terminal, configured to input the electrical signal output by the signal shaping circuit module. The inverting input of high-speed differential comparator U4 is connected to resistor R12 and capacitor C9 in sequence. Capacitor C9 is further grounded. The connection point between resistor R12 and capacitor C9 is set as the second signal input terminal, used to input the electrical signal output by the peak hold circuit module. Typically, high-speed differential comparator U4 can be powered by a symmetrical ±VCC / VEE power supply, with AGND providing an analog reference ground. The output terminal of high-speed differential comparator U4 is connected to resistor R9. Resistor R9 is further connected to one end of resistor R14 and capacitor C10 in parallel. The other end of resistor R14 and capacitor C10 in parallel is grounded. The connection point between resistor R9 and resistor R14 and capacitor C10 is set as the output terminal, outputting a square wave signal.

[0080] Typically, after filtering and peak holding by the signal shaping and peak holding circuits, the electrical signal enters the signal discrimination circuit module. The function of the signal discrimination circuit module is to filter out noise, identify the useful signal, and output a square wave pulse signal with a width equivalent to the signal. The core component of the signal discrimination circuit is the high-speed differential comparator U4. Alpha and beta ray signal pulses have steep leading edges, often on the order of nanoseconds, thus requiring high speed from the voltage comparator, while also possessing low noise characteristics. Resistor R8 is a current-limiting resistor, protecting the input terminal from overvoltage damage to the comparator; the inverting input signal passes through an RC filter composed of resistor R12 and capacitor C9, filtering out input noise and preventing false triggering; resistor R13 is a single-function pull-down resistor, ensuring the input is not floating or drifting, allowing the high-speed differential comparator U4 to stably output a "normal" state when there is no signal. SCR_LE is a digital signal derived from the LE control port of the high-speed differential comparator U4, controlling whether the SCR gate can be triggered, and transmitted to the host computer. The EN control port of the high-speed differential comparator U4 is grounded. Resistor R6 is connected in series in the SCR main current loop to convert the current flowing through the SCR into voltage, which is used for instantaneous overcurrent judgment at the second input terminal IN2 of the high-speed differential comparator U4. When the input pulse amplitude exceeds the set threshold, the comparator outputs a high level; when the input pulse amplitude is lower than the threshold, it outputs a low level. The output terminal is current-limited by resistor R9 and filtered by resistor R14 and capacitor C10 to optimize the edge characteristics of the square wave, and finally outputs a standard TTL square wave signal SCR_COMP1, the width of which is used in the FPGA to distinguish the α and β signals.

[0081] FPGA, or Field-Programmable Gate Array, is a semiconductor device whose hardware logic functions can be defined through programming. The FPGA is the core of the FPGA data processing module, distinguishing the widths of α and β signals using a constant-time-ratio method. After processing by the aforementioned circuit, the pulse widths of the α and β signals differ significantly: the α pulse is greater than 20ns, while the β pulse is less than 20ns. Therefore, the FPGA can use a simple clock counting method to measure the pulse width. The maximum measurement error is the period of the FPGA system clock; the higher the clock frequency, the smaller the measurement error and the higher the accuracy. The FPGA can use a 50 MHz external clock crystal, multiplied to 200 MHz by an internal phase-locked loop. Therefore, the maximum error in pulse width measurement is 5ns, which is within the acceptable range of system error and meets the system design requirements. Typically, the direct pulse counting method uses a constant-time-ratio to measure pulse width, such as... Figure 5 As shown.

[0082] Some embodiments disclose alpha and beta particle discrimination systems based on liquid scintillation counters.

[0083] Some embodiments disclose α and β particle discrimination methods based on liquid scintillation counters, implemented by the α and β particle discrimination system based on liquid scintillation counters disclosed in the embodiments of the present invention. The method includes:

[0084] Detecting electrical signals from alpha and beta particles;

[0085] The detected electrical signals of α and β particles are shaped;

[0086] The shaped electrical signal is then subjected to peak amplification and hold processing.

[0087] Filter out noise and identify useful signals;

[0088] The useful signal is processed to convert the "pulse width" to a "square wave". By adjusting the discrimination threshold of the square wave width, the α and β particles can be counted separately.

[0089] Furthermore, some embodiments disclose an α and β particle discrimination method based on a liquid scintillation counter, in which the useful signal is a square wave signal, and the pulse width of the waveform signal is used to distinguish α and β particles.

[0090] Some embodiments disclose alpha and beta particle discrimination methods based on liquid scintillation counters, utilizing... 241 Am (α standard source) and 90 Sr- 90Experimental measurements were conducted using a Y (β standard source). Both the β and α sources were placed in the counting system, and the operating modes of either the α or β source were set. By adjusting the discrimination threshold of the FPGA, the relationship between the crosstalk ratio of α rays to the β channel and the crosstalk ratio of β rays to the α channel under different α and β discrimination thresholds was obtained. The crosstalk ratio is used to calculate the false counts caused by α signals entering the β counting channel or β signals entering the α counting channel. The crosstalk ratio is an important indicator for measuring the discrimination performance of the instrument, and its calculation method is as follows:

[0091] Method for calculating the cross-channel ratio of α-rays to β-channels:

[0092]

[0093] Method for calculating the cross-channel ratio of β-rays to α-channel:

[0094]

[0095] In the formula, n β,avg n is the average count within channel β; α,avg The average count within channel α.

[0096] The method provided in this embodiment achieves an alpha particle count crosstalk ratio of 2.82% and a β particle count crosstalk ratio of 1.65%, demonstrating equivalent counting accuracy compared to existing discrimination methods using analog circuits. The results are as follows... Figure 6 .

[0097] The α and β particle discrimination method and system based on a liquid scintillation counter disclosed in this invention features a discrimination circuit designed based on a constant-time ratio method, achieving α and β particle discrimination and counting with a false discrimination rate of less than 3%. The discrimination and counting of α and β particles are implemented directly in pure hardware, with response speed limited only by comparator and switching delays, resulting in a total time of <50ns. No high-speed ADC is required, significantly reducing power consumption and cost. Dual capacitor holding allows for independent measurement of wide and narrow pulse energy, facilitating subsequent counting, waveform reconstruction, or closed-loop control. The threshold, gain, and low-pass cutoff frequency can all be adjusted via resistors and capacitors to adapt to different width threshold values.

[0098] The technical solutions and technical details disclosed in the embodiments of this invention are merely illustrative of the inventive concept of this invention and do not constitute a limitation on the technical solutions of the embodiments of this invention. Any conventional changes, substitutions, or combinations made to the technical details disclosed in the embodiments of this invention have the same inventive concept as this invention and are within the protection scope of the claims of this invention.

Claims

1. A liquid scintillator based alpha, beta particle discrimination system, characterized in that, The utility model relates to a kind of alpha beta particle signal acquisition system, including: Signal detection module for detecting alpha, beta particle electric signal; Signal shaping circuit module, connected with the signal detection module, for shaping the detected alpha, beta particle electric signal; Peak holding circuit module, connected with the signal shaping circuit module, for amplifying and peak holding processing of the shaped alpha, beta particle electric signal; Signal discrimination circuit module, connected with the signal shaping circuit module and peak holding circuit module respectively, for discriminating useful electric signal of alpha, beta particle; FPGA data processing module, connected with the signal discrimination circuit module, for distinguishing square wave signal corresponding to alpha, beta particle.

2. A liquid scintillator counter based alpha, beta particle discrimination system according to claim 1, wherein, The signal shaping circuit module includes: Operational amplifier U3;The noninverting input of the operational amplifier U3 is configured as an electrical signal input terminal, and a resistor R16 and a capacitor C13 are connected in parallel between the inverting input and the output of the operational amplifier U3;The output of the operational amplifier U3 is further provided with a resistor R10 and a resistor R11 connected in series; Analog multiplexer U6;The S1, S2, S3, S4 and S5 ports of the analog multiplexer U6 are respectively provided with a resistor R20, a resistor R21, a resistor R19, a resistor R24 and a resistor UR2 connected thereto, and the resistor R20, the resistor R21, the resistor R19, the resistor R24 and the resistor UR2 are further connected in common between the resistor R10 and the resistor R11; Operational amplifier U5;The noninverting input of the operational amplifier U5 is provided with a resistor R7 connected thereto, and the resistor R7 is further grounded;The inverting input of the operational amplifier U5 is provided with the resistor R11 connected thereto;A resistor R15 and a capacitor C11 are connected in parallel between the inverting input and the output of the operational amplifier U5;The inverting input of the operational amplifier U5 is further provided with the D interface of the analog multiplexer connected thereto.

3. A liquid scintillator counter based alpha, beta particle discrimination system according to claim 1, wherein, The peak holding circuit module includes: Operational amplifier U8;The noninverting input of the operational amplifier U8 is provided with a resistor R17 connected thereto, and the resistor R17 is further connected with the signal output terminal of the signal shaping module;A capacitor C21 and a resistor R30 are connected in series between the inverting input and the output of the operational amplifier U8;A diode D2 is further connected in parallel between the inverting input and the output of the operational amplifier U8; Operational amplifier U7;The inverting input of the operational amplifier U7 is provided with a resistor R22 connected thereto, and the resistor R22 is further connected with the output of the operational amplifier U7;The noninverting input of the operational amplifier U7 is provided with a resistor R27 connected thereto, and the resistor R27 is further connected with a resistor R28 and a resistor R29, the resistor R28 is connected with a capacitor C16, the resistor R29 is connected with a capacitor C18, and the capacitor C16 and the capacitor C18 are further connected with each other and grounded. The output end of the operational amplifier U8 is further provided with a diode D1, and the diode D1 is further provided with a connection point connected with the resistors R27, R28 and R29; the non-inverting input end of the operational amplifier U8 is further provided with a connection point connected with the diode D1 and the resistors R27, R28 and R29; and the connection point of the non-inverting input end of the operational amplifier U8 and the diode D1 is further provided with a resistor R26, and the resistor R26 is further provided with a connection with the output end of the operational amplifier U7; The connection point of the resistor R22 and the output end of the operational amplifier U7 is further provided with a resistor R23, and the resistor R23 is further provided with a resistor UR1, and the other end of the resistor UR1 is provided with a ground, and the active end of the resistor UR1 is provided as a signal output end of the peak value holding circuit module.

4. The liquid scintillator counter based alpha, beta particle discrimination system of claim 1, wherein, The signal discrimination circuit module comprises: A high-speed differential comparator U4; the non-inverting input end of the high-speed differential comparator U4 is provided with resistors R8 and R13 connected in sequence, the resistor R13 is provided with a ground, and the resistor R8 and the resistor R13 are provided as a first signal input end for inputting a telecommunication signal output by the signal shaping circuit module; and the inverting input end of the high-speed differential comparator U4 is provided with resistors R12 and a capacitor C9 connected in sequence, the capacitor C9 is further provided with a ground, and the connection point between the resistor R12 and the capacitor C9 is provided as a second signal input end for inputting a telecommunication signal output by the peak value holding circuit module; The output end of the high-speed differential comparator U4 is provided with a resistor R9, the resistor R9 is further provided with a connection with one end of a resistor R14 and a capacitor C10 connected in parallel, and the other end of the resistor R14 and the capacitor C10 connected in parallel is provided with a ground; and the connection point of the resistor R9, the resistor R14 and the capacitor C10 is provided as an output end for outputting a square wave signal.

5. A method for alpha, beta particle discrimination based on a liquid scintillation counter, implemented by the alpha, beta particle discrimination system based on a liquid scintillation counter according to any one of claims 1-4, characterized in that the method It comprises: Detecting alpha and beta particle telecommunication signals; Shaping the detected alpha and beta particle telecommunication signals; Performing peak value amplification and holding processing on the shaped telecommunication signals; Filtering out noises and discriminating useful signals; Performing data processing on the discriminated useful signals to realize separate counting of alpha and beta particles.

6. A liquid scintillator counter based alpha, beta particle discrimination method according to claim 5, wherein, The discriminated useful signals are square wave signals, and the pulse width of the wave signals is used to discriminate alpha and beta particles.

7. A liquid scintillator counter based alpha, beta particle discrimination method according to claim 6, characterized in that, The data processing on the discriminated useful signals comprises: The relationship between the corresponding alpha ray to beta channel channel ratio and the beta ray to alpha channel channel ratio under different alpha and beta discrimination threshold conditions; wherein, Alpha ray to beta channel channel ratio calculation method: ； Beta ray to alpha channel channel ratio calculation method: ； where n β,avg is the average value of the counts in the beta channel; n α,avg is the average value of the counts in the alpha channel.

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