Bnct gamma dose measurement system based on sCVD diamond

Abstract

The application discloses a BNCT gamma dose measurement system based on sCVD diamond, wherein a sCVD diamond detector signal is transmitted to a radio frequency amplifier for conditioning and amplification, the amplified analog signal is converted into a digital signal by a high-speed ADC and is transmitted to an FPGA for processing, a trigger threshold is set to obtain effective radiation signals, and each radiation signal data point is collected; waveform data collected by the ADC is transmitted to an upper computer, discrimination of gamma signals and acquisition of air absorption dose data are completed in the upper computer, firstly, the radiation signals are subjected to filtering and normalization processing; secondly, the processed radiation signals are input into a neutron-gamma discrimination program for processing, and the radiation signals in the discrimination results are input into an air absorption dose conversion program to obtain final gamma dose information. The application integrates the functions of a diamond detector, an ADC and an FPGA, cooperates with modularized design of each part, so that the detection method can realize real-time collection in a high-dose-rate neutron gamma mixed field, can effectively discriminate gamma signals and can obtain a gamma dose rate, and has high practicability.

Description

Technical Field

[0001] This invention belongs to the field of ionizing radiation detection technology. Specifically, it relates to a method for detecting gamma signals in a high-dose neutron-gamma mixed field. Background Technology

[0002] BNCT is a type of radiotherapy used to treat cancer that relies on the nuclear reaction between neutrons and the boron-10 isotope to precisely kill tumor cells. Because this reaction primarily occurs within boron-containing cells, BNCT can target and kill cancer cells without damaging healthy tissue. It is particularly suitable for treating cancers that are difficult to cure with surgery or conventional radiotherapy, such as brain tumors and head and neck cancers. In addition to a large number of neutrons, the BNCT beam also emits gamma rays of a certain energy intensity, requiring real-time measurement of the gamma dose to ensure that the patient's absorbed dose remains within a safe range.

[0003] As a third-generation semiconductor, diamond has advantages such as a wider bandgap, larger atomic shift energy, high electron and hole mobility and saturation drift velocity, resistance to high temperature and high pressure, chemical stability, fast signal response and insensitivity to light. These advantages enable diamond detectors to perform radiation measurements in harsh nuclear environments such as reactor cores, accelerator beams and strong radiation fields. In addition, due to the different energy deposition modes of neutrons and gamma rays in diamond, the shapes of the pulse signals they generate in diamond are different, giving diamond the ability to distinguish between neutrons and gamma rays.

[0004] Currently, radiation detector systems using diamond detectors to measure gamma ray dose in the mixed field of BNCT are still in the research and development stage. The BNCT treatment environment contains a complex mixed radiation field, including thermal neutrons, fast neutrons, and gamma rays. Gamma ray dose assessment is crucial for the safety and accuracy of treatment, as excessive gamma radiation can damage normal tissues. This invention's detector system, capable of accurately measuring gamma ray dose, is of great significance for the clinical application and dose management of BNCT. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned defects or deficiencies in the prior art and provide a BNCT gamma dose measurement system based on sCVD diamond for detecting gamma signals in high-dose neutron-gamma mixed fields. This aims to enable the diamond detector to operate in single-pulse mode under single-probe conditions, thereby achieving the detection of gamma dose rate in high-dose mixed fields. This invention achieves its purpose through the following technical solution:

[0006] A BNCT gamma dose measurement system based on sCVD diamond is characterized by comprising a detection module, a data acquisition module, and a human-computer interaction module;

[0007] The detection module includes: an sCVD diamond detector, a bias circuit, a current preamplifier circuit, a signal conditioning circuit, and a shielding module. The sCVD diamond detector consists of a single-crystal diamond probe, a signal conditioning circuit, a data acquisition unit, a power supply circuit, and a host computer. Gamma rays and neutron rays interact with the sCVD diamond detector to generate electron-hole pairs. Under the action of an additional electric field, the electrons and holes drift in opposite directions, generating a pulsed current signal. The bias circuit is connected to the sCVD diamond detector, and the external high-voltage electric field is regulated by the bias circuit before being connected to the diamond detector. The detector provides an external electric field for the drift of electrons and holes in the diamond detector; the current preamplifier circuit is connected to the sCVD diamond detector and amplifies the current pulse signal output by the sCVD diamond detector and converts it into a voltage pulse signal; the signal conditioning circuit is connected to the current preamplifier circuit and conditions the voltage pulse signal output by the current preamplifier circuit to the voltage range adapted by the ADC; the shielding module is used to shield external radiation and environmental electromagnetic interference, protect the electronic components on the current preamplifier circuit, and prevent the electronic components from being interfered with or damaged.

[0008] The data acquisition module includes an ADC and an FPGA; the ADC converter is used to convert the analog signal input to the ADC by the conditioning circuit into a digital signal; the FPGA is used to monitor the core pulse digital signal data stream of the ADC in real time and transmit the waveform information to the host computer via USB;

[0009] The human-computer interaction module, connected to the data acquisition module, includes a USB serial port and a host computer. The host computer receives the pulse signal data stream transmitted by the FPGA through the USB serial port and decodes the data to obtain waveform data. By eliminating neutron pulse signals based on pulse shape differences, the gamma pulse signals are left, thereby obtaining the gamma dose rate and displaying it in real time.

[0010] Furthermore, the sCVD diamond detector and the current preamplifier circuit are AC coupled. AC coupling can isolate the leakage current of the detector, prevent the DC drift of the signal baseline, and ensure that the baseline of the pulse signal remains stable, which is beneficial to signal processing.

[0011] Furthermore, the sCVD diamond probe consists of an sCVD diamond of a certain thickness and a metal shielding cover; the signal conditioning circuit consists of a high signal-to-noise ratio RF preamplifier circuit and a high voltage circuit.

[0012] Furthermore, the shielding module is composed of a neutron shielding layer, a photon shielding layer, and an aluminum alloy layer in a certain proportion and thickness, which reduces the incident neutron and gamma dose rate to a range within which the device can operate normally, isolates the bias circuit, and reduces environmental interference coupled to the signal.

[0013] Furthermore, the host computer can process a large amount of data stream from FPGA 10 in real time, and through program processing, exclude the neutron signal and retain only the γ signal to obtain the gamma dose rate and display the information.

[0014] Furthermore, the detection module is connected to the data acquisition module via an adjustable-length coaxial cable, placing the data acquisition module away from the radiation source, thus reducing the number of modules that need to be shielded.

[0015] Furthermore, the host computer is an industrial control computer with programming capabilities.

[0016] Furthermore, the card acquisition device consists of a high-speed ADC acquisition board and an FPGA circuit board.

[0017] Furthermore, the power supply circuit provides power to the signal conditioning circuit and the card reader.

[0018] Secondly, the present invention also includes a measurement method for a BNCT gamma dose measurement system based on sCVD diamond, comprising the following steps:

[0019] Step 1: Measure the neutron-gamma in the BNCT mixed field using an sCVD diamond detector and a card reader. Obtain the effective radiation signal through overthreshold triggering and collect each radiation signal data point.

[0020] Step 2: Transmit the effective radiation signal to the host computer via serial communication;

[0021] Step 3: In the host computer, perform filtering and normalization preprocessing on the radiation signal;

[0022] Step 4: In the host computer, perform neutron-gamma discrimination on the preprocessed radiation signal;

[0023] Step 5: In the host computer, the signal identified as gamma is processed to calculate and obtain the gamma air absorption dose;

[0024] Step 6: In the host computer, display the final obtained gamma air absorption dose in the software interface.

[0025] Furthermore, the serial communication described in step 2 uses analog signal and / or digital signal level standards for data transmission.

[0026] Compared with existing technologies, the method of detecting gamma signals in a high-dose neutron-gamma complex field of the present invention integrates the functions of diamond detector, ADC and FPGA and the modular design of each part, so that the detection method can quickly collect and exclude neutron signals in a high-dose-rate neutron-gamma complex field to obtain the gamma dose rate, which is highly practical. Attached Figure Description

[0027] Figure 1 This is a structural block diagram of a BNCT gamma dose measurement system based on sCVD diamond according to the present invention;

[0028] Figure 2 This is a schematic diagram of the shielding module structure of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the present invention;

[0030] Reference numerals: 1-Detection module, 2-Data acquisition module, 3-Human-machine interaction module, 4-Diamond detector, 5-Bias circuit, 6-Current preamplifier circuit, 7-Shielding module, 8-Conditioning circuit, 9-ADC, 10-FPGA, 11-USB, 12-Host computer, 13-SMA interface, 14-Coaxial cable, 15-Acquisition board. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0032] It should be noted that, unless otherwise explicitly stated, the terms "connected," "linked," "installed," and "transmitted" should be interpreted broadly. For example, "connected" can refer to an electrical connection or a mechanical connection; "installed" can refer to a connection using an intermediate medium or an integrated installation of a structure. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Figure 1 The diagram shows a system structure block diagram of a method for detecting gamma signals in a high-dose neutron-gamma mixed field according to a preferred embodiment of the present invention, including a detection module 1, a data acquisition module 2, and a human-computer interaction module 3.

[0034] refer to Figure 3The detection module 1 includes a diamond detector 4, a bias circuit 5, a current preamplifier circuit 6, a shielding module 7, and a conditioning circuit 8. The diamond detector 4 is an integral unit, and its power supply and signal lines are led out through an SMA interface 13 and connected to the bias circuit. The bias circuit 5, the current preamplifier circuit 6, and the conditioning circuit 8 are packaged on a PCB board.

[0035] The shielding module mentioned above is as follows Figure 2 As shown, the outermost neutron shielding material, the innermost photon shielding material, and the innermost aluminum alloy layer form a whole, which together with the bias circuit 5, the current preamplifier circuit 6, and the conditioning circuit 8 form a whole.

[0036] The data acquisition module 2 is connected to the detection module 1, and the data acquisition module 2 is packaged on a PCB, which includes an ADC 9 and an FPGA 10.

[0037] The human-computer interaction module 3 includes a USB 11 and a host computer 12; the USB 11 is connected to the FPGA 10 of the data acquisition module 2, and the other end of the USB 11 is connected to the host computer 12.

[0038] The power module 13 is connected to the detection module 1 and the data acquisition module 2, and is used to supply power to each module.

[0039] In this embodiment, the charge carriers generated by the ionization of the diamond detector 4 after being irradiated by gamma rays and neutron rays migrate under the guidance of the external electric field applied by the bias circuit 5 and are collected by the electrodes to generate a current pulse signal.

[0040] The aforementioned current pulse signal enters the current preamplifier circuit 6. The two-stage RF amplifier circuit in the current preamplifier circuit 6 amplifies the current pulse signal and converts it into a voltage pulse signal. Then, the conditioning circuit 8 adjusts the voltage pulse signal to a suitable amplitude and converts the single-ended signal into a differential signal to adapt to the input mode of the ADC 9. The ADC 9 digitizes the differential voltage pulse signal and transmits it to the FPGA 10. The FPGA 10 compares the input data stream with a preset threshold one by one. When a signal is found to be greater than the threshold, it records a fixed time window and sends the waveform information data stream to the host computer. For measuring the gamma dose rate, the response R is defined as:

[0041]

[0042] k is a fixed constant, C is the count rate, and D is the dose rate. R represents the ratio of the dose rate measured by the diamond detector to the actual dose rate. Since R is very small within the dose rate range, the deviation between the dose rate measured by the diamond detector and the actual dose rate is small. For diamond, there is a good linear relationship between the dose rate and the count rate, indicating that the diamond detector performs excellently in dose response and can directly convert the total count rate to the dose rate.

[0043] In this embodiment, by setting up USB 11, the diamond gamma detector can establish bidirectional communication with the host computer via a wired connection and share gamma dose rate and cumulative gamma dose information.

[0044] In some preferred embodiments, the structure of the method for detecting gamma signals is as follows: Figure 3 As shown, except for the diamond detector 4, all other parts of the detection module 1 are encapsulated in the shielding module 7. The diamond detector 4 is connected to the bias circuit 5 through the SMA interface. The conditioning circuit 8 of the detection module 1 is connected to the ADC 9 of the data acquisition module 2 through the adjustable length coaxial cable 14.

[0045] Compared with existing technologies, the method of detecting gamma signals in a high-dose neutron-gamma complex field of the present invention integrates the functions of diamond detector, ADC and FPGA and the modular design of each part, so that the detection method can quickly collect and exclude neutron signals in a high-dose-rate neutron-gamma complex field to obtain the gamma dose rate, which is highly practical.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A BNCT gamma dosimetry system based on sCVD diamond, characterized in that, It consists of a detection module, a data acquisition module, and a human-computer interaction module; The detection module includes: an sCVD diamond detector, a bias circuit, a current preamplifier circuit, a signal conditioning circuit, and a shielding module. The sCVD diamond detector consists of a single-crystal diamond probe, a signal conditioning circuit, a card reader, a power supply circuit, and a host computer. Gamma rays and neutron rays interact with the sCVD diamond detector to generate electron-hole pairs. Under the action of an additional electric field, electrons and holes drift in opposite directions, generating pulsed current signals. The bias circuit is connected to the sCVD diamond detector. An external high-voltage electric field is regulated by the bias circuit and then connected to the diamond detector to provide an external electric field for the drift of electrons and holes in the diamond detector. The current preamplifier circuit is connected to the sCVD diamond detector to amplify the current pulse signal output by the sCVD diamond detector and convert it into a voltage pulse signal. The signal conditioning circuit is connected to the current preamplifier circuit and is used to condition the voltage pulse signal output by the current preamplifier circuit to the voltage range adapted by the ADC; the shielding module is used to shield external radiation and environmental electromagnetic interference, protect the electronic components on the current preamplifier circuit, and prevent the electronic components from being interfered with or damaged; the detection module is connected to the data acquisition module through an adjustable coaxial cable, placing the data acquisition module away from the radiation source, thus reducing the number of shielding modules required; The data acquisition module includes an ADC and an FPGA; the ADC converter is used to convert the analog signal input to the ADC by the conditioning circuit into a digital signal; the FPGA is used to monitor the core pulse digital signal data stream of the ADC in real time and transmit the waveform information to the host computer via USB; The human-computer interaction module, connected to the data acquisition module, includes a USB serial port and a host computer. The host computer receives the pulse signal data stream transmitted by the FPGA through the USB serial port and decodes the data to obtain waveform data. By eliminating neutron pulse signals based on pulse shape differences, the gamma pulse signals are left, thereby obtaining the gamma dose rate and displaying it in real time.

2. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The sCVD diamond detector and the current preamplifier circuit are AC coupled. AC coupling can isolate the leakage current of the detector, prevent DC drift of the signal baseline, and ensure that the baseline of the pulse signal remains stable, which is beneficial to signal processing.

3. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The sCVD diamond probe consists of an sCVD diamond of a certain thickness and a metal shielding cover; the signal conditioning circuit consists of a high signal-to-noise ratio RF preamplifier circuit and a high voltage circuit.

4. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The shielding module is composed of a neutron shielding layer, a photon shielding layer, and an aluminum alloy layer in a certain proportion and thickness. It reduces the incident neutron and gamma dose rate to a range that allows the device to operate normally, isolates the bias circuit, and reduces environmental interference coupled to the signal.

5. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The host computer can process a large amount of data stream from FPGA 10 in real time, and through program processing, exclude the neutron signal and retain only the γ signal to obtain the gamma dose rate and display the information.

6. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The host computer is an industrial control computer with programming capabilities.

7. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The card acquisition device consists of a high-speed ADC acquisition board and an FPGA circuit board.

8. The BNCT gamma dosimetry system based on sCVD diamond according to claim 1, characterized in that, The power supply circuit provides power to the signal conditioning circuit and the card reader.

9. A measurement method for a BNCT gamma dosimetry system based on sCVD diamond, characterized in that, Includes the following steps: Step 1: Measure the neutron-gamma in the BNCT mixed field using an sCVD diamond detector and a card reader. Obtain the effective radiation signal through overthreshold triggering and collect each radiation signal data point. Step 2: Transmit the effective radiation signal to the host computer via serial communication; Step 3: In the host computer, perform filtering and normalization preprocessing on the radiation signal; Step 4: In the host computer, perform neutron-gamma discrimination on the preprocessed radiation signal; Step 5: In the host computer, the signal identified as gamma is processed to calculate and obtain the gamma air absorption dose; Step 6: In the host computer, display the final obtained gamma air absorption dose in the software interface.

10. The measurement method of the BNCT gamma dosimetry system based on sCVD diamond according to claim 9, characterized in that, The serial communication described in step 2 uses analog and / or digital signals for data transmission.

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