Double-wire proportional counter tube, signal processing method and ray measuring device

Abstract

The invention relates to the technical field of radiation detection, and discloses a double-wire proportional counter tube and a signal processing method thereof. The double-wire proportional counter tube comprises a cavity made of TU2 oxygen-free copper, two 50 [mu] m gold-plated tungsten wires are arranged in the cavity in parallel to serve as anode wires, the distance between the wires is 1.8 cm, and the anode wires are led out through ceramic insulation terminals. And P10 gas is filled in the cavity. And the signal processing module comprises a pre-amplification circuit, a coincidence circuit, a main amplification circuit and a data acquisition unit, and is used for carrying out coincidence processing on the two paths of anode signals and screening effective signals. The signal processing method comprises the steps of gas ionization, electron avalanche amplification and signal synchronous judgment and recording. The ray measuring device integrates the counting tube, a gas path system and a data acquisition system, background noise is reduced through a coincidence circuit, and an energy spectrum analysis module can be selected to distinguish alpha rays and beta rays. The invention has the advantages of simple structure, high sensitivity, low background noise and the like.

Description

Technical Field

[0001] This invention relates to the field of radiation detection technology, and in particular to a dual-wire proportional counter tube and its signal processing method, as well as a low-background α and β ray measurement device based on the counter tube, which is applicable to environmental monitoring, nuclear radiation detection and low-background radioactivity measurement. Background Technology

[0002] In the field of radiation monitoring, alpha and beta rays are two types of radiation that require key monitoring in radiometric measurements. Low-concentration alpha and beta radioactive sources are widely present in people's production and living environments, such as the air we breathe, drinking water, vegetables we eat, soil, as well as samples from decommissioned nuclear facilities, reactor surroundings, isotope-related products, import and export goods, and biological samples. These can all be contaminated by weak alpha and beta radioactive sources or are themselves weak alpha and beta radioactive sources. Therefore, effective monitoring of low-concentration alpha and beta rays is of great significance for safeguarding people's health and well-being.

[0003] Currently, three main detection methods are used in this field both domestically and internationally: scintillator detectors, gas flow counters, and semiconductor detectors. Among them, the core component of the gas flow counter is the gas flow proportional counter tube. However, traditional gas flow proportional counter tubes suffer from high background and low detection efficiency, which makes it easy to produce large errors when measuring low-activity samples, making it difficult to meet the needs of accurate monitoring.

[0004] A traditional gas-flow proportional counter tube consists of a cathode housing, an anode wire, insulated fixed terminals, anode wire leads, and gas inlet and outlet ports. Its specific drawbacks are as follows:

[0005] The casing material is usually stainless steel or brass. Under the condition that the gas flow counter is filled with P10 gas for a long time, these materials are prone to corrosion, which will release impurity gases and negatively charged gases (such as oxygen, water vapor, etc.), resulting in an increase in the background of the counting tube.

[0006] The anode wire is typically a gold-plated tungsten wire located at the center of the axis, and its sensitive volume is limited. For large-area samples with a diameter of φ50~φ60mm, due to the end effect (particles are ionized at the edge of the counter tube, and some electrons are lost in the non-sensitive area) and the chamber wall effect, some particles lose energy outside the sensitive volume, resulting in a smaller pulse amplitude and thus reducing the detection efficiency.

[0007] Because of the aforementioned problems with traditional gas flow proportional counters, their application in measuring total α and total β at low background levels is limited. Therefore, there is an urgent need for a gas flow proportional counter that can solve the problems of high background and low detection efficiency. Summary of the Invention

[0008] One objective of this invention is to provide a dual-wire proportional counter tube that effectively reduces noise interference and improves detection efficiency through a dual-anode wire design combined with coincidence measurement technology. Simultaneously, the use of a high-purity oxygen-free copper cathode and an optimized gas filling scheme further enhances the stability and sensitivity of the counter tube.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This invention discloses a dual-wire proportional counter tube, comprising a cavity, two anode wires, and a signal processing module; the cavity is made of oxygen-free copper; the two anode wires are arranged in parallel within the cavity; the leads of the anode wires are ceramic insulated terminals; the signal processing module includes a preamplifier circuit, a coincidence circuit, a main amplifier circuit, and a data acquisition unit, used to perform coincidence processing on the signals from the two anode wires and record the signals detected simultaneously by the two anode wires.

[0011] In addition to the above-mentioned technical features, the present invention has also made optimizations and improvements in the following aspects:

[0012] As a preferred embodiment of the present invention, the cavity is made of TU2 oxygen-free copper, and the oxygen content of the TU2 oxygen-free copper is not greater than 0.003%.

[0013] As a preferred embodiment of the present invention, the radius of the cavity is 40-50 mm.

[0014] As a preferred embodiment of the present invention, the anode wire is a 50μm gold-plated tungsten wire, and the wire-to-wire distance between the two anode wires is 16-19 mm / cm.

[0015] As a preferred embodiment of the present invention, the ceramic insulating terminal includes:

[0016] A ceramic sleeve, the inner diameter of which matches the anode wire;

[0017] The copper tube lead-out end is sintered and sealed with the ceramic sleeve, and is electrically connected to the preamplifier.

[0018] The cavity is filled with P10 gas. The P10 gas is a mixture of 90% argon and 10% methane.

[0019] A second objective of this invention is to provide a signal processing method for a dual-wire proportional counter tube, comprising:

[0020] X-rays ionize the P10 gas in the cathode chamber to produce electrons;

[0021] Electrons drift to the two anode wires and trigger avalanche amplification;

[0022] The two anode wires output electrical signals to the preamplifier circuit for preliminary amplification;

[0023] The two signals are synchronized and judged by a matching circuit to filter out the valid signal;

[0024] The valid signal is amplified twice by the main amplifier circuit and then recorded by the data acquisition unit.

[0025] A third objective of this invention is to provide a radiation measuring device, comprising the aforementioned dual-wire proportional counter tube, a gas path system for supplying P10 gas thereto, and a data acquisition system, wherein the data acquisition system receives the output signal of the coincidence circuit and records the count.

[0026] As a preferred embodiment of the present invention, the data acquisition system further includes an energy spectrum analysis module for performing energy spectrum analysis on the recorded signals to distinguish between α and β rays.

[0027] Based on the above description of the technical content, the dual-wire proportional counter tube, signal processing method, and X-ray measuring device of this application achieve significant technical effects through a series of technical features, specifically reflected in the following aspects:

[0028] 1. Significantly reduces background noise and improves the accuracy of low activity measurements.

[0029] Material optimization for background suppression: Using TU2 oxygen-free copper as the chamber material (oxygen content ≤0.003%), its extremely low impurity content effectively reduces the release of impurity gases (such as hydrogen and oxygen) within the chamber, avoiding the corrosion and gas release problems caused by long-term filling of P10 gas (90% argon + 10% methane) with traditional stainless steel and brass shells. This not only maintains the purity and stability of the P10 gas but also reduces the capture of electrons by negatively charged gases (such as O2), lowering the background noise. This meets the stringent requirements for low-background-level total α and total β measurements.

[0030] The noise filtering effect of the dual-wire coincidence circuit: The coincidence circuit of the signal processing module synchronously judges the signals of the two anode wires and records only the valid signals that arrive at the same time. This can effectively eliminate noise signals that are falsely triggered by a single wire (such as random interference and invalid pulses caused by edge effects), further reduce the false count rate, and ensure the accuracy of the measurement results of low activity samples.

[0031] 2. Improve detection efficiency and reduce energy loss

[0032] Expanded sensitive volume of dual anode wire structure: Two 50μm gold-plated tungsten wires (wire spacing 16-19mm) are arranged in parallel inside the cavity (radius 40-50mm). Compared with the traditional single anode wire structure, the sensitive volume is significantly expanded, and the energy loss caused by end effect (electron loss in non-sensitive area due to particle ionization at the edge) and chamber wall effect is reduced.

[0033] Stability assurance for signal amplification and transmission: The anode wire lead-out end adopts ceramic insulated terminals (ceramic sleeve + copper tube sintered seal), which not only ensures high voltage insulation performance, but also achieves stable signal transmission through the copper tube, reducing signal attenuation or interference, and ensuring that weak X-ray signals (low concentration α and β rays) can be effectively captured and amplified.

[0034] 3. Enhance system stability and applicability

[0035] Long-term stability of the gas environment: The improved compatibility of the oxygen-free copper shell with P10 gas reduces changes in gas composition caused by material corrosion, extends the stable working time of the counting tube, and reduces the need for frequent gas changes or maintenance.

[0036] Wide range of application scenarios: With its low background and high efficiency, this invention can meet the measurement needs of various low-activity α and β radioactive sources such as air, water, soil, biological samples, and decommissioned nuclear facility samples, providing reliable technical support for radiation monitoring (such as environmental safety, import and export inspection, reactor monitoring, etc.).

[0037] 4. Synergistic optimization of structure and process

[0038] The composite insulation terminal design of ceramic and copper tube achieves the dual functions of high-voltage sealing and signal transmission, solving the problems of easy air leakage and signal interference in traditional insulation structures; the matching design of the dual wire parameters (spacing and diameter) and cathode size ensures the uniformity of electric field distribution, further improving the energy resolution and signal consistency of the counting tube.

[0039] In summary, this invention achieves a technological breakthrough of "low background, high efficiency, and high stability" through multi-dimensional innovative design in materials, structure, and signal processing, effectively solving the bottleneck problem of traditional gas flow proportional counter tubes in the measurement of low activity α and β. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure of the dual-wire proportional counter tube of the present invention;

[0041] Figure 2 yes Figure 1 Sectional view along axis AA;

[0042] Figure 3 This is a side view of the dual-wire proportional counter tube of the present invention;

[0043] Figure 4 yes Figure 3 BB-direction sectional view;

[0044] Figure 5 This is a flowchart of the signal processing method for the dual-wire proportional counter tube of the present invention.

[0045] In the diagram: 1. Cavity; 2. Anode wire one; 3. Anode wire two; 4. Ceramic insulating terminal; 5. Copper tube lead-out end; 6. Air inlet; 7. Air outlet; 8. Preamplifier circuit; 9. Composite circuit; 10. Main amplifier circuit; 11. Data acquisition unit. Detailed Implementation

[0046] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] I. Explanation of descriptive terms used in this invention

[0048] The embodiments provided in conjunction with the technical solutions of this invention are intended to make the invention more thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that unless otherwise specifically stated in this invention, the relative arrangements of components described in these embodiments should be interpreted as merely exemplary and not as a limitation on the technical solutions of this invention.

[0049] In this invention, when directional terms such as "up," "down," "left," "right," "bottom," and "top" are used, they are defined relative to the directions shown in the accompanying drawings and are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. These or other directional terms should not be construed as restrictive terms.

[0050] In this invention, the terms "a," "an," "an," "the," and similar words used do not indicate quantity limitations and can represent singular or plural. The terms "comprising," "including," "having," and any variations thereof used in this invention are intended to cover non-exclusive inclusion; the terms "first," "second," "third," etc., used in this invention are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0051] In this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0052] Furthermore, this invention does not discuss in detail the technologies and equipment known to those skilled in the art, but where appropriate, such technologies and equipment should be considered part of the specification.

[0053] II. The core technical problem to be solved by the technical solution of this application

[0054] In the current field of radiation monitoring, traditional gas-flow proportional counters have significant problems. Their structure consists of a cathode shell, an anode wire, and other parts. However, the shell material is often stainless steel or brass, which is prone to corrosion under the condition of long-term filling of P10 gas in the gas-flow counter. This corrosion releases impurities and negatively charged gases, resulting in an increase in the background of the counter.

[0055] Meanwhile, the anode wire is a gold-plated tungsten wire at the center of the axis, and the sensitive volume is limited. For large-area samples with a diameter of φ50~φ60mm, due to the end effect (particles are ionized at the edge of the counting tube, and some electrons are lost in the non-sensitive area) and the chamber wall effect, some particle energy is lost outside the sensitive volume, resulting in a smaller pulse amplitude and reduced detection efficiency.

[0056] These problems limit the application of traditional gas flow proportional counters in the measurement of total α and total β at low background levels, making it difficult to meet the needs of accurate monitoring. Therefore, there is an urgent need to develop a new type of gas flow proportional counter that can solve the problems of high background and low detection efficiency.

[0057] III. Based on the above problems, the present invention specifically provides a technical solution to solve these problems. The following describes specific embodiments and references the appendix. Figure 1-5 As shown, the technical solution, working principle, and technical effects of the present invention will be explained in detail.

[0058] Example 1

[0059] like Figure 4 As shown, the dual-wire proportional counter tube of this embodiment includes a cavity 1, anode wire one 2, anode wire two 3, ceramic insulating terminal 4, copper tube lead-out end 5, air inlet 6, air outlet 7, and a signal processing module.

[0060] The signal processing module includes: a preamplifier circuit 8, a coincidence circuit 9, a main amplifier circuit 10, and a data acquisition unit 11.

[0061] Among them, anode wire 1 2 and anode wire 2 3 are arranged in parallel inside the cavity 1, and both ends are fixed by ceramic insulating terminals 4; the copper tube lead-out end 5 is sintered and sealed with the ceramic insulating terminal 4, and is connected to the preamplifier circuit 8 through a signal line; the air inlet 6 and the air outlet 7 are respectively arranged on both sides of the cavity 1 for introducing and discharging P10 gas.

[0062] The cavity 1 is made of TU2 oxygen-free copper and has a cylindrical structure with a radius of 40-50 mm (suitable for sample sizes of φ50-φ60 mm).

[0063] TU2 oxygen-free copper has an oxygen content of no more than 0.003% and extremely low impurity content, which can effectively reduce the release of impurity gases such as hydrogen and oxygen inside the cavity and maintain the stability of gas purity inside the cavity.

[0064] Both anode wire 12 and anode wire 23 are gold-plated tungsten wires with a diameter of 50μm and a gold plating layer thickness of 2μm (to enhance conductivity and corrosion resistance).

[0065] Two anode wires are arranged in parallel with a wire spacing of 16-19 mm. Both ends are fixed to the two ends of the cavity 1 through ceramic insulating terminals 4 and are kept insulated from the cavity 1.

[0066] Ceramic insulating terminal 4 and copper tube lead-out terminal 5: Ceramic insulating terminal 4 is an Al2O3 ceramic sleeve with an inner diameter matching the diameter of the anode wire (50μm) to ensure that the anode wire does not wobble when passing through; copper tube lead-out terminal 5 is a copper tube (2mm in diameter) that is sealed to the ceramic sleeve by high-temperature sintering (sealing strength ≥0.5MPa). One end is welded to the anode wire for conduction, and the other end is connected to the preamplifier circuit 8 through a shielded signal line.

[0067] Gas path structure: Both the inlet 6 and outlet 7 are brass interfaces (4mm in diameter), which are connected to the external gas path system through PTFE pipes for continuous introduction of P10 gas (90% argon + 10% methane). The gas flow rate is controlled at 50mL / min to ensure stable gas purity in the chamber.

[0068] Signal processing module: The preamplifier circuit 8 uses a charge-sensitive preamplifier (model CR-110) to amplify the weak electrical signal (mV level) output by the anode wire to the V level; the coincidence circuit 9 is a dual-channel synchronous judgment circuit (response time ≤10ns), which only determines a valid signal when the time difference between the two signals is ≤5ns; the main amplification circuit 10 is a pulse amplifier (adjustable gain, range 10~1000), which further amplifies the signal to the range that the data acquisition unit can recognize; the data acquisition unit 11 is a multichannel analyzer (sampling rate 100MHz), used to record the count of valid signals and pulse amplitude.

[0069] In conjunction with the above description, and to more clearly illustrate the technical solution of this application, the working principle of the technical solution involved in this invention is explained below:

[0070] like Figure 5 As shown, after the rays (α or β rays) enter cavity 1, they ionize the P10 gas inside, producing electron-ion pairs.

[0071] Electrons drift toward the anode wire in the electric field formed by cavity 1 and the anode wire (applied positive voltage, 1500V). When they reach the vicinity of the anode wire, they trigger avalanche amplification, which enhances the weak current signal.

[0072] Anode wire 1 2 and anode wire 2 3 respectively transmit the amplified electrical signal to the preamplifier circuit 8 through the copper tube lead-out terminal 5, and after preliminary amplification, it is input into the comparator circuit 9;

[0073] The circuit 9 synchronizes the two signals and determines that they are valid signals from the same ray only when the two signals arrive at the same time (time difference ≤ 5ns), thus avoiding duplicate counting.

[0074] After the effective signal is amplified twice by the main amplifier circuit 10, the data acquisition unit 11 records the count and pulse amplitude to complete the X-ray detection.

[0075] Based on the above structure and working principle, this embodiment achieves the following effects:

[0076] Low background: The TU2 oxygen-free copper cavity reduces impurity gas release, and with the help of a dual-wire coincidence circuit, the background test data is 0.31~0.67cpm (see Table 1), which is significantly lower than that of traditional stainless steel cavity proportional counter tubes (β background ≤1cpm).

[0077] Currently, conventional airflow proportional counters on the market have a detection area of ​​φ50~φ60mm, and can achieve a β background of ≤1cpm under 4π10cm lead chamber shielding and anti-coincidence conditions, as shown in model LND-49567. The dual-wire proportional counter proposed in this application can achieve an even lower background and meets the Poisson distribution test.

[0078] Table 1 Baseline Test Data

[0079] Number of measurements 1 2 3 4 5 6 7 8 9 Background (cpm) 0.49 0.47 0.48 0.67 0.40 0.38 0.35 0.42 0.38 Number of measurements 10 11 12 13 14 15 16 17 18 Background (cpm) 0.43 0.31 0.41 0.38 0.34 0.38 0.52 0.48 0.62

[0080] High detection efficiency: The dual anode wire design increases the sensitive volume, improving the detection efficiency by about 15% compared to a single-wire proportional counter tube.

[0081] High resolution: Reduced negatively charged gases (such as oxygen) result in less loss during electron drift, improved pulse amplitude stability, and a 20% increase in α / β ray resolution.

[0082] Example 2

[0083] The main difference between this embodiment and Embodiment 1 is the difference in the anode wire spacing and the cavity radius: in Embodiment 1, the anode wire spacing is 16-19 mm and the cathode radius is 40-50 mm, while in this embodiment, the anode wire spacing is 20 mm and the cavity radius is 55 mm.

[0084] Anode wire spacing: The spacing between anode wire 1 (2) and anode wire 2 (3) is adjusted to 20mm, with a parallelism error ≤0.1mm, to ensure uniform electric field distribution.

[0085] The cavity has an increased radius of 55mm and is made of TU2 oxygen-free copper (oxygen content ≤0.003%), making it suitable for samples with a larger area (φ60~φ70mm).

[0086] The remaining structures (such as anode wire diameter, ceramic insulating terminals, signal processing modules, etc.) are the same as in Example 1.

[0087] The working principle is the same as in Example 1, except that the larger cathode radius and anode wire spacing further increase the sensitive volume (by about 12% compared to Example 1), which can cover a larger sample area and reduce the counting loss caused by the sample edge exceeding the sensitive area.

[0088] By employing a larger anode wire spacing and cathode radius, this embodiment achieves the following effects:

[0089] Higher detection efficiency: The increased sensitive volume improves the detection efficiency of φ60~φ70mm samples by about 5% compared to Example 1 (i.e., about 20% compared to the single-wire proportional counter tube), making it suitable for large-size sample measurement;

[0090] Slightly increased background: The increased chamber volume leads to a longer diffusion path for impurity gases, resulting in a background test data of 0.40–0.70 cpm, which is still lower than that of traditional counting tubes;

[0091] Improved compatibility: Adapts to larger sample areas, allowing direct measurement without sample trimming, reducing sample processing errors.

[0092] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications can be made without departing from the core concept of the present invention (such as adjusting the diameter of the anode wire to 40 μm, or the proportion of methane in the P10 gas to 12%), and these modifications all fall within the protection scope of the present invention.

[0093] Example 3

[0094] This embodiment adds an energy spectrum analysis function to the signal processing module to distinguish between α and β rays.

[0095] Data acquisition system: Based on Example 1, an energy spectrum analysis module is integrated to perform energy spectrum analysis on the recorded signals.

[0096] Software algorithm: Distinguish between alpha rays (high amplitude) and beta rays (low amplitude) through pulse amplitude analysis.

[0097] Technical effect description: The addition of the energy spectrum analysis module enables this embodiment to simultaneously measure and distinguish between α and β rays, making it suitable for complex radioactive environments.

[0098] Tests show that the accuracy of distinguishing between alpha and beta rays is over 95%, further expanding the application scenarios.

[0099] The above embodiments, through optimization of cathode materials, dual-anode wire design, and signal processing algorithms, significantly reduced background noise (≤0.5 cpm), improved detection efficiency (by 10%–15%), and achieved the ability to distinguish between α / β rays. Embodiment 1 is the basic scheme, while Embodiments 2 and 3 provide extended schemes for high-energy rays and multifunctional requirements, respectively, covering a wider range of application scenarios.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0101] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A dual-wire proportional counter tube, characterized in that, The device includes a cavity (1), two anode wires, and a signal processing module. The cavity (1) is made of oxygen-free copper. The two anode wires are arranged in parallel inside the cavity (1). The lead-out ends of the anode wires are ceramic insulated terminals (4). The signal processing module includes a preamplifier circuit (8), a coincidence circuit (9), a main amplifier circuit (10), and a data acquisition unit (11), which is used to perform coincidence processing on the signals of the two anode wires and record the signals detected by the two anode wires simultaneously.

2. The dual-wire proportional counter tube according to claim 1, characterized in that, The cavity (1) is made of TU2 oxygen-free copper, and the oxygen content of the TU2 oxygen-free copper is not greater than 0.003%.

3. The dual-wire proportional counter tube according to claim 1 or 2, characterized in that, The radius of the cavity (1) is 40-50 mm.

4. The dual-wire proportional counter tube according to claim 1, characterized in that, The anode wire is a 50μm gold-plated tungsten wire, and the distance between the two anode wires is 16-19mm.

5. The dual-wire proportional counter tube according to claim 1, characterized in that, The ceramic insulating terminal (4) includes: A ceramic sleeve, the inner diameter of which matches the anode wire; The copper tube lead-out end (5) is sintered and sealed with the ceramic sleeve and electrically connected to the preamplifier.

6. The dual-wire proportional counter tube according to claim 3, characterized in that, The cavity (1) is filled with P10 gas.

7. The dual-wire proportional counter tube according to claim 6, characterized in that, The P10 gas is a mixture of 90% argon and 10% methane.

8. A signal processing method for a dual-wire proportional counter tube, characterized in that, Includes the following steps: Electrons are generated in the P10 gas within the X-ray ionization chamber; Electrons drift to the two anode wires and trigger avalanche amplification; The two anode wires output electrical signals to the preamplifier circuit (8) for preliminary amplification; The two signals are synchronized and the valid signal is filtered by the matching circuit (9); The valid signal is amplified twice by the main amplifier circuit (10) and then recorded by the data acquisition unit (11).

9. A radiation measuring device, characterized in that, It includes a dual-wire proportional counter tube as described in any one of claims 1 to 7, a gas path system and a data acquisition system for providing P10 gas thereto, wherein the data acquisition system receives the output signal of the coincidence circuit (9) and records the count.

10. The radiation measuring device according to claim 9, characterized in that, The data acquisition system also includes an energy spectrum analysis module, which is used to perform energy spectrum analysis on the recorded signals to distinguish between α and β rays.

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