Pulse charged particle beam dose monitoring system and monitoring method thereof

Abstract

The invention relates to a pulse charged particle beam dose monitoring system and a monitoring method thereof.The pulse charged particle beam dose monitoring system comprises an ACCT sensor, a signal conditioning module, a high-speed data acquisition module and a data processing and interaction module, the ACCT sensor is installed on a beam vacuum pipeline, and the output end of the ACCT sensor is connected to the signal conditioning module; the output end of the signal conditioning module is connected to the high-speed data acquisition module, and the output end of the high-speed data acquisition module is connected with the data processing and interaction module; the method comprises the following steps: carrying out system calibration to obtain a conversion coefficient k in a preset signal-dose conversion relation; performing dose-time spectrum real-time monitoring and analysis by adopting a system; and obtaining a dose-time spectrum of the charged particle beam. By adopting the system and the method disclosed by the embodiment of the invention, real-time and non-destructive monitoring on the beam pulse time structure and the corresponding dose-time distribution can be realized, so that support and guarantee are provided for accurate dose control and safe treatment.

Description

Technical Field

[0001] This invention belongs to the field of ionizing radiation metrology, specifically relating to a pulsed charged particle beam dose monitoring system and its monitoring method. Background Technology

[0002] Due to its advantages such as ease of acceleration and adjustable dose rate, pulsed electron beams demonstrate significant value in specific applications, particularly in generating pulsed photon beams and several specialized applications. Pulsed electron beams generate bremsstrahlung radiation by hitting a target, efficiently producing pulsed photon beams (such as X-rays and gamma rays). In medical imaging, these pulsed photon beams offer microsecond-level temporal resolution, enabling the capture of high-resolution images of dynamic organ processes such as heartbeats. In industrial inspection, they can penetrate thick-walled metal components to achieve high-speed, real-time defect detection, such as online flaw detection of pipe welds. In scientific research, pulsed photon beams can also be used to simulate high-energy photon environments in astrophysical processes, studying the interaction mechanisms between photons and matter.

[0003] Due to their high instantaneous dose rate and specific temporal structure, pulsed proton beams and heavy ion beams have become key technologies in FLASH radiotherapy and related scientific research. In FLASH radiotherapy, pulsed proton / heavy ion beams, with their high instantaneous dose rate, can significantly reduce damage to normal tissues while maintaining a high tumor-killing effect, thus achieving the so-called FLASH effect. Combined with the unique Bragg peak energy release characteristics of heavy ion beams and their temporal structure that can be synchronized with physiological activities such as respiration, this technology can achieve precise radiotherapy in both spatial and temporal dimensions, making it particularly suitable for the clinical treatment of refractory tumors. In scientific research, these pulsed particle beams can be used to simulate space radiation, nuclear accident scenarios, and extreme material irradiation environments, providing crucial experimental tools for radiation biology, materials science, and fundamental physics research.

[0004] In the measurement of time structure, pulsed charged particle beam technology faces severe challenges. Its applications require precise characterization of the beam's time dimension, with measurement accuracy reaching sub-millisecond or even nanosecond levels, while ensuring the stability of radiation performance parameters during the pulse. Existing technologies primarily monitor steady-state beams, and their inability to effectively respond to the dynamic characteristics of pulsed beams has become a technological bottleneck restricting its development.

[0005] Currently, monitoring technologies applicable to pulsed beams are mainly divided into two categories: interception and non-interception. Interception monitoring, represented by ionization chambers, can accurately measure the total dose of a single pulse, but because its charge collection time is much longer than the pulse duration, its response speed is slow and it cannot capture the instantaneous changes in dose within the pulse. Therefore, it is difficult to obtain the crucial "dose-time spectrum," limiting the dynamic dose control capability in high-dose-rate scenarios. Offline measurement devices, such as thermoluminescent dosimeters, can only provide cumulative dose information and cannot achieve real-time data output. Therefore, they cannot meet the needs of "real-time monitoring" and "pulse time structure analysis" in pulsed beam applications such as real-time dose feedback in FLASH radiotherapy and online defect identification in industrial flaw detection. Summary of the Invention

[0006] The purpose of this invention is to provide a pulsed charged particle beam dose monitoring system and method, which can monitor the temporal structure of the pulsed charged particle beam in real time without interfering with the beam current, and analyze the fine dose-time distribution (i.e., dose-time spectrum) during the pulse, thereby providing support and guarantee for precise dose control and safe treatment.

[0007] Specifically, by constructing a quantitative correlation model between non-interceptor device signals and dose-time spectra, accurate inversion from beam intensity time distribution to dose time distribution is achieved. While maintaining the advantage of non-interceptor monitoring without beam loss, it meets the stringent requirements for real-time dose analysis in high-dose-rate and high-stability application scenarios such as heavy ion FLASH radiotherapy and high-energy photon scientific research experiments.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, a pulsed charged particle beam dose monitoring system, the system comprising a broadband ACCT sensor, a signal conditioning module, a high-speed data acquisition module, and a data processing and interaction module, wherein the broadband ACCT sensor is directly mounted on the beam vacuum pipe via a flange, the output end of the broadband ACCT sensor is connected to the input end of the signal conditioning module, the output end of the signal conditioning module is connected to the input channel of the high-speed data acquisition module, and the output end of the high-speed data acquisition module is connected to the data processing and interaction module;

[0009] The wideband ACCT sensor is used to sense beam pulses in a non-intercepting manner and output a broadband weak current signal corresponding to the time change rate of beam intensity.

[0010] The signal conditioning module is used to condition the broadband weak current signal output by the broadband ACCT sensor into a voltage signal with a high signal-to-noise ratio.

[0011] The high-speed data acquisition module is used to acquire and digitize the conditioned voltage signal at a preset sampling frequency to obtain a high-resolution discrete sequence of beam intensity changing over time.

[0012] The data processing and interaction module is used to convert beam intensity data into air kerma or absorbed dose based on a preset signal-dose conversion relationship using built-in dose-time spectrum analysis software, and then reconstruct and display the waveform of dose distribution over time in real time, thus obtaining the beam dose-time spectrum.

[0013] Furthermore, the signal conditioning module includes a transimpedance amplifier circuit and a low-pass filter circuit;

[0014] The transimpedance amplifier circuit is used to convert the broadband weak current signal output by the broadband ACCT sensor into a voltage signal.

[0015] The low-pass filter circuit is used to suppress high-frequency noise in the voltage signal and effectively improve the signal-to-noise ratio of the voltage signal while preserving the original time characteristics.

[0016] Furthermore, the feedback resistor R f The size is set according to the beam current intensity and the number of turns of the wideband ACCT sensor coil.

[0017] Furthermore, the high-speed data acquisition module includes a high-speed ADC and an FPGA device.

[0018] Furthermore, the high-speed data acquisition module includes a digital oscilloscope.

[0019] Furthermore, the data processing and interaction module is also used to automatically extract dose-related key parameters, including peak pulse dose rate, pulse width, rise time, fall time, and total dose per pulse.

[0020] Furthermore, the preset signal-dose conversion relationship in the data processing and interaction module is as follows:

[0021]

[0022] Where D is the dose, k is the conversion factor, and V out (t) represents the output voltage of the transimpedance amplifier. R f For the feedback resistor, I ind (t) represents the induced current, I ind (t) = I b (t) / N, I b (t) represents the beam current intensity, and N represents the number of turns of the wideband ACCT sensor coil.

[0023] Secondly, a method for monitoring dose of a pulsed charged particle beam, the method employing a pulsed charged particle beam dose monitoring system as described in the first aspect of the present invention and any optional embodiment thereof, the method comprising the following steps:

[0024] S1. Perform system calibration to obtain the conversion coefficient k in the preset signal-dose conversion relationship in the data processing and interaction module;

[0025] S2. Based on the obtained conversion coefficient k, the system is used for real-time monitoring and analysis of the dose-time spectrum.

[0026] Furthermore, step S1 includes the following sub-steps:

[0027] S11, Draw out the known beam intensity I b A single or series of beam pulses (t) are used to measure a known beam intensity I. b The cumulative absorbed dose of the beam pulse (t) is used as the reference dose D. ref ;

[0028] S12. Calculate the total beam charge: Q total =∫I b (t) dt;

[0029] S13, Based on total beam charge Q total and reference dose D ref Calculate the conversion factor k: k=D ref / Q total .

[0030] Furthermore, step S2 includes the following sub-steps:

[0031] S21. Acquire the beam pulses of charged particles and obtain the voltage-time series V of beam intensity changing with time from the high-speed data acquisition module. out [n];

[0032] S22, Based on the acquired voltage time series V out [n], beam reconstruction is performed according to a preset formula to obtain a discrete beam intensity sequence I. b [n];

[0033] S23. Based on the conversion coefficient k, perform dose conversion to convert the beam intensity sequence I. b [n] is converted to a dose rate sequence. DoseRate[n] = k × I b [n];

[0034] S24. Generate the curve of DoseRate[n] changing with time, which gives the dose-time spectrum of the charged particle beam.

[0035] The beneficial technical effects of this invention are as follows: For the first time, the temporal structure information of the beam is systematically integrated with dosimetric measurements to generate a "dose-time spectrum." This completely overcomes the technical deficiency of existing technologies (such as ionization chambers) that can only provide a single "total dose per pulse" integral. Through the dose-time spectrum, users can clearly and intuitively observe how the dose dynamically distributes over time within pulse durations on the order of microseconds or even nanoseconds, thus revealing the fine structure within the pulse and providing a completely new data perspective for understanding the correlation between beam characteristics and biological effects and physical experimental results.

[0036] Unlike traditional dose monitoring systems that can only determine whether the total dose delivered by a single pulse exceeds the limit, the pulsed charged particle beam dose monitoring system disclosed in this invention allows the system to make more precise safety judgments during pulse delivery. For example, the system can determine in real time whether the peak dose rate of the pulse exceeds the safety threshold, whether the pulse shape is distorted, and whether the dose distribution over time matches the expected treatment plan. This achieves an upgrade from "total control" to "process control," enabling earlier and more sensitive detection of equipment anomalies and greatly improving the safety level of treatment.

[0037] This invention discloses a pulsed charged particle beam dose monitoring system that inherits all the advantages of ACCT (Air-Core Current Transformer) non-interception measurement: zero beam interference, no radiation damage, long lifespan, and simple maintenance. Simultaneously, by introducing and calibrating a precise "dose-to-beam-current conversion coefficient k," the relative measurement capability of ACCT is correlated with an absolute dose standard, resulting in a "single-pulse total dose" output with a certain degree of absolute accuracy. Furthermore, it provides dose-time spectrum information that ionization chambers cannot provide, thus achieving a comprehensive combination of advantages.

[0038] The core device of this invention is a mature ACCT and commercially available high-speed acquisition equipment, and the core method is a well-defined signal integration and mapping algorithm. The entire system does not rely on complex or expensive special components, and is easy to integrate and verify on existing treatment devices or experimental platforms, laying a solid foundation for its rapid promotion in scientific research, medical and industrial fields. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of a pulsed charged particle beam dose monitoring system according to Embodiment 1 of the present invention. Detailed Implementation

[0040] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] like Figure 1 As shown, this embodiment of the invention provides a pulsed charged particle beam dose monitoring system, including an ACCT sensor, a signal conditioning module, a high-speed data acquisition module, and a data processing and interaction module. The ACCT sensor is directly mounted on the beam vacuum pipeline via a flange. The output end of the ACCT sensor is connected to the input end of the signal conditioning module, the output end of the signal conditioning module is connected to the input channel of the high-speed data acquisition module, and the output end of the high-speed data acquisition module is connected to the data processing and interaction module.

[0043] In this embodiment of the invention, the ACCT sensor uses a broadband beam transformer of the Bergoz Instrumentation ACCT or FCT type, but in fact, there is no limitation on this.

[0044] The ACCT sensor is suitable for monitoring pulsed beams with pulse widths in the microsecond to nanosecond range. The ACCT sensor is directly mounted on the beam vacuum line via a flange, located in the beam diagnostic section.

[0045] The signal conditioning module uses a custom-designed PCB board, which includes a transimpedance amplifier circuit and a low-pass filter circuit.

[0046] The core component of the transimpedance amplifier circuit is a high-speed operational amplifier such as the TI OPA847 or OPA657, configured in transimpedance amplification mode, with feedback resistor R. f The size is set according to the beam current intensity and the number of turns of the ACCT sensor coil. In this embodiment of the invention, the feedback resistor R... f It has a size of 1 kΩ and is equipped with a second-order Butterworth low-pass filter with a cutoff frequency of 10 MHz.

[0047] The high-speed data acquisition module uses a custom-designed PCB board, with core components being a high-speed ADC and FPGA. Alternatively, a Tektronix MSO64B digital oscilloscope can be used, with a sampling rate of 2.5 GS / s and an analog bandwidth of 500 MHz, to ensure accurate capture of pulse leading edges.

[0048] The data processing and interaction module is used to run pre-stored dose-time spectrum analysis software. In this embodiment of the invention, the dose-time spectrum analysis software, which is independently developed based on the Python language, is run on a workstation equipped with an Intel i7 processor.

[0049] The ACCT sensor senses beam pulses in a non-interceptive manner and outputs a broadband weak current signal corresponding to the time-varying rate of beam intensity. The broadband weak current signal output by the ACCT sensor is then input to the signal conditioning module for conditioning. The conditioned voltage signal is acquired and digitized by the high-speed data acquisition module at a sampling rate of not less than 100 MHz to obtain a high-resolution discrete sequence of beam intensity changing with time.

[0050] The specific steps of the broadband weak current signal input signal conditioning module include first converting it into a voltage signal through a transimpedance amplifier circuit, and then suppressing high-frequency noise through a low-pass filter circuit, effectively improving the signal-to-noise ratio while preserving the original time characteristics.

[0051] In the data processing and interaction module, the built-in dose-time spectrum analysis software converts the beam intensity data into air kerma or absorbed dose based on the preset signal-dose conversion relationship, and then reconstructs and displays the waveform of dose distribution over time (i.e., dose-time spectrum) in real time, and automatically extracts key parameters including pulse peak dose rate, pulse width, rise / fall time and total dose per pulse.

[0052] The system uses the following physical and mathematical models for measurement and calibration:

[0053]

[0054]

[0055]

[0056] Among them, I b (t) represents the beam current intensity, N represents the number of turns in the sensor coil, and I Vin S(t) is the induced current, V out (t) represents the output voltage of the transimpedance amplifier, R f Let D(t) be the feedback resistor, D(t) be the dose, and k be the conversion coefficient. By obtaining the conversion coefficient k through experimental calibration, the entire system can be precisely calibrated, ensuring the accuracy and traceability of dose measurements.

[0057] Example 2

[0058] This invention provides a method for monitoring the dose of a pulsed charged particle beam. The method employs a pulsed charged particle beam dose monitoring system as described in Embodiment 1 and any optional embodiment thereof. The method includes the following steps:

[0059] S1. Perform system connection and initial setup, signal conditioning and acquisition parameter configuration, and system calibration.

[0060] In this embodiment of the invention, the output of the ACCT sensor is connected to the input of the signal conditioning module using a 50Ω coaxial cable. The output of the conditioning module is then connected to the input channel of a high-speed oscilloscope via a cable of the same specification. The oscilloscope is connected to the data processing workstation via a GPIB or Ethernet interface.

[0061] Since the output impedance of the ACCT sensor and the input impedance of the signal conditioning module are generally 50Ω, a 50Ω coaxial cable is selected in this embodiment of the invention to ensure impedance matching. In fact, the resistance value of the coaxial cable is not limited, and the resistance value of the coaxial cable is matched with the output impedance of the ACCT sensor and the input impedance of the signal conditioning module.

[0062] Turn on the power to all devices and analyze the characteristics of the pulsed beam under test.

[0063] In this embodiment of the invention, the expected pulse width is set to 2 μs and the peak current intensity is 10 nC / μs, but in fact, there is no limitation on this.

[0064] In this embodiment of the invention, the oscilloscope's vertical range is set to 500 mV / div, the time base to 500 ns / div, and a high-resolution acquisition mode is enabled to improve the signal-to-noise ratio. In fact, this is not a limitation; the goal is simply to ensure that the waveform can be accurately and completely observed on the oscilloscope screen. Specific settings need to be determined in conjunction with factors such as beam intensity.

[0065] The trigger mode was set to edge trigger, and the trigger level was adjusted to 150 mV to ensure stable capture of each beam pulse.

[0066] Step S1 includes the following sub-steps:

[0067] S11, Draw out the known beam intensity I b A single or series of beam pulses (t) are used to measure a known beam intensity I. b The cumulative absorbed dose of the beam pulse (t) is used as the reference dose D. ref ；

[0068] A calibrated standard dosimeter was temporarily installed downstream of the ACCT sensor to measure the cumulative absorbed dose of the beam pulse.

[0069] S12. Calculate the total beam charge: Q total =∫Ib (t) dt .

[0070] S13. Calculate the system conversion coefficient: k=D ref / Q total .

[0071] The k value is stored in the analysis software's configuration file and used for dose calculation in all subsequent measurements, after which the ionization chamber is removed.

[0072] S2. Perform real-time monitoring and analysis of the dose-time spectrum.

[0073] The system enters real-time monitoring mode. For each acquired beam pulse, step S2 includes the following sub-steps:

[0074] S21, Data Acquisition

[0075] Reading voltage time series V from an oscilloscope out [n], the raw output V of the ACCT sensor out(t) ∝ Beam current intensity I b (t).

[0076] S22, Perform beam reconstruction

[0077] According to the formula Calculate the discrete beam intensity sequence I b [n]. Where N is the fixed turns ratio of ACCT.

[0078] S23, Perform dose conversion

[0079] Based on the calibration coefficient k, the beam sequence is converted into a dose rate sequence: DoseRate[n] = k × I b [n].

[0080] S24. Generating Spectra and Extracting Parameters

[0081] Plot the curve of DoseRate[n] changing over time in real time, i.e., the dose-time spectrum.

[0082] The spectrum is automatically analyzed, and the following parameters are extracted:

[0083] Pulse peak dose rate: the maximum value of DoseRate[n].

[0084] Pulse width (FWHM): The full width of the pulse at 50% peak dose rate.

[0085] Rise time: The time required for the dose rate to rise from 10% to 90% peak.

[0086] Total dose per pulse: numerically integrated on the DoseRate[n] curve.

[0087] As can be seen from the above embodiments, the pulsed charged particle beam dose monitoring system and method disclosed in this invention successfully achieves precise measurement of the dose distribution within a single proton beam pulse. Users can not only obtain accurate total dose per pulse, but also intuitively observe instantaneous dose changes from the real-time dose-time spectrum, accurately capturing details of the pulse's rising edge, peak, and falling edge. This effectively solves the limitation of traditional ionization chambers in being unable to resolve the pulse time structure, providing crucial data support for dosimetric research and safety control of advanced radiotherapy technologies such as flash therapy.

[0088] The system and monitoring method described in this invention are not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solution of this invention also fall within the scope of technical innovation of this invention.

Claims

1. A pulsed charged particle beam dose monitoring system, characterized in that: The system includes an ACCT sensor, a signal conditioning module, a high-speed data acquisition module, and a data processing and interaction module. The ACCT sensor is installed on the beam vacuum pipe. The output end of the ACCT sensor is connected to the input end of the signal conditioning module. The output end of the signal conditioning module is connected to the input channel of the high-speed data acquisition module. The output end of the high-speed data acquisition module is connected to the data processing and interaction module. The ACCT sensor is used to sense beam pulses in a non-intercepting manner and output a broadband weak current signal corresponding to the time change rate of beam intensity. The signal conditioning module is used to condition the broadband weak current signal output by the ACCT sensor into a voltage signal with a high signal-to-noise ratio. The high-speed data acquisition module is used to acquire and digitize the conditioned voltage signal at a preset sampling frequency to obtain a high-resolution discrete sequence of beam intensity changing over time. The data processing and interaction module is used to convert beam intensity data into air kerma or absorbed dose according to a preset signal-dose conversion relationship, and then reconstruct and display the waveform of dose distribution over time in real time, thus obtaining the beam dose-time spectrum.

2. The pulsed charged particle beam dose monitoring system as described in claim 1, characterized in that: The signal conditioning module includes a transimpedance amplifier circuit and a low-pass filter circuit. The transimpedance amplifier circuit is used to convert the broadband weak current signal output by the broadband ACCT sensor into a voltage signal. The low-pass filter circuit is used to suppress high-frequency noise in the voltage signal and effectively improve the signal-to-noise ratio of the voltage signal while preserving the original time characteristics.

3. The pulsed charged particle beam dose monitoring system as described in claim 2, characterized in that: Feedback resistor R f The size is set according to the beam current intensity and the number of turns of the wideband ACCT sensor coil.

4. The pulsed charged particle beam dose monitoring system as described in claim 1, characterized in that: The high-speed data acquisition module includes a high-speed ADC and an FPGA device.

5. The pulsed charged particle beam dose monitoring system as described in claim 1, characterized in that: The high-speed data acquisition module includes a digital oscilloscope.

6. The pulsed charged particle beam dose monitoring system as described in claim 1, characterized in that: The data processing and interaction module is also used to automatically extract dose-related key parameters, including peak pulse dose rate, pulse width, rise time, fall time, and total dose per pulse.

7. The pulsed charged particle beam dose monitoring system as described in claim 6, characterized in that: The preset signal-dose conversion relationship in the data processing and interaction module is as follows: Where D is the dose, k is the conversion factor, and V out (t) represents the output voltage of the transimpedance amplifier. R f For the feedback resistor, I ind (t) represents the induced current, I ind (t) = I b (t) / N, I b (t) represents the beam current intensity, and N represents the number of turns of the ACCT sensor coil.

8. A method for monitoring the dose of a pulsed charged particle beam, the method employing a pulsed charged particle beam dose monitoring system as described in any one of claims 1-7, the method comprising the following steps: S1. Perform system calibration to obtain the conversion coefficient k in the preset signal-dose conversion relationship in the data processing and interaction module; S2. Based on the obtained conversion coefficient k, the system is used for real-time monitoring and analysis of the dose-time spectrum.

9. The pulsed charged particle beam dose monitoring method as described in claim 8, characterized in that, Step S1 includes the following sub-steps: S11, Draw out the known beam intensity I b A single or series of beam pulses (t) are used to measure a known beam intensity I. b The cumulative absorbed dose of the beam pulse (t) is used as the reference dose D. ref ; S12. Calculate the total beam charge: Q total =∫I b (t) dt; S13, based on total beam charge Q total and reference dose D ref Calculate the conversion factor k: k=D ref / Q total .

10. The pulsed charged particle beam dose monitoring method as described in claim 8, characterized in that, Step S2 includes the following sub-steps: S21. Acquire the beam pulses of charged particles and obtain the voltage-time series V of beam intensity changing with time from the high-speed data acquisition module. out [n]; S22, Based on the acquired voltage time series V out [n], beam reconstruction is performed according to a preset formula to obtain a discrete beam intensity sequence I. b [n]; S23. Based on the conversion coefficient k, perform dose conversion to convert the beam intensity sequence I. b [n] is converted to a dose rate sequence. DoseRate[n] = k × I b [n]; S24. Generate the curve of DoseRate[n] changing with time, which gives the dose-time spectrum of the charged particle beam.

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