Digital energy spectrum and flux system for Tokamak hard X-ray measurement

Abstract

The invention relates to the technical field of Tokamak hard X-ray measurement, in particular to a digital energy spectrum and flux system for Tokamak hard X-ray measurement. According to the technical scheme, the device comprises a hemispherical tellurium-zinc-cadmium detector used for receiving hard X-rays generated by fast electrons in plasma and ionizing the hard X-rays to generate charges; the charge sensitive preamplifier is connected with the hemispherical tellurium-zinc-cadmium detector and is used for converting charges generated by the detector into voltage signals; the shaping amplifier is connected with the charge-sensitive pre-amplifier and is used for shaping and amplifying the voltage signal; and the digital multichannel analyzer and integrator is connected with the shaping amplifier. The system is compact, an existing hard X-ray energy spectrum and flux measuring system is simplified, more detectors and acquisition systems can be conveniently installed on the Tokamak, therefore, the spatial resolution of hard X-ray diagnosis is improved, and meanwhile, the system integration degree is high, and the system maintainability and maintenance efficiency are high.

Description

Technical Field

[0001] The present invention relates to the technical field of tokamak hard X-ray measurement, and in particular to a digital energy spectrum and flux system for tokamak hard X-ray measurement. Background Art

[0002] In the Tokamak, fast electron and escape electron measurement play a very important role. Low noise generates fast electrons through Landau damping. Fast electrons carry plasma current to achieve non-inductive current drive and achieve steady-state operation of plasma. When the plasma breaks, escape electrons are generated. If the escape electrons hit the Tokamak vacuum components, they may damage these components. Therefore, it is necessary to monitor the escape electrons.

[0003] On a tokamak, hard X-ray measurement is the most important means of measuring fast electrons and escaped electrons. Fast electrons and escaped electrons produce hard X-rays through bremsstrahlung, and hard X-ray measurement can obtain the energy and intensity information of fast electrons and escaped electrons.

[0004] Semiconductor detectors are currently used on most tokamaks to measure hard X-rays because of their advantages such as high energy resolution, resistance to magnetic field interference, and operation at room temperature.

[0005] There are currently two ways to measure the energy spectrum and flux of hard X-rays in Tokamaks. One way is to use two detectors. The signal of one detector is amplified by a preamplifier and an energy spectrum amplifier and then enters a multi-channel analyzer to collect the energy spectrum. The signal of the other detector is amplified by a current amplifier and then enters an acquisition card for flux collection. Another way is to use one detector. The signal of the detector is amplified by a preamplifier and an energy spectrum amplifier and then enters a multi-channel analyzer to collect the energy spectrum. The signal from the energy spectrum amplifier simultaneously enters a detector to obtain the signal envelope, and then the flux is collected by an acquisition card.

[0006] Both hard X-ray energy spectrum and flux measurement methods require two sets of hardware systems. The first method requires two detectors and two amplifiers, and the second method requires a detector. Both methods also require an acquisition card for flux acquisition. The space available for diagnosis on the tokamak is limited. The current two hard X-ray energy spectrum and flux measurement methods cannot guarantee sufficient spatial resolution, so new energy spectrum and flux measurement methods need to be developed.

[0007] In summary, the present application proposes a digital energy spectrum and flux system for tokamak hard X-ray measurement. Summary of the invention

[0008] The purpose of the present invention is to address the problem in the background technology that the two current hard X-ray energy spectrum and flux measurement methods cannot guarantee sufficient spatial resolution, and to propose a digital energy spectrum and flux system for tokamak hard X-ray measurement.

[0009] The technical solution of the present invention is a digital energy spectrum and flux system for tokamak hard X-ray measurement, comprising:

[0010] Hemispherical CdZnTe detector, used to receive hard X-rays generated by fast electrons in plasma and ionize them to generate charges;

[0011] A charge-sensitive preamplifier connected to the hemispherical cadmium zinc telluride detector and used for converting the charge generated by the detector into a voltage signal;

[0012] a shaping amplifier connected to the charge sensitive preamplifier to shape and amplify the voltage signal;

[0013] A digital multi-channel analyzer and integrator, connected to the shaping amplifier, performs multi-channel analysis and digital integration;

[0014] The acquisition and control software installed on the host computer is used to receive signals from the digital multi-channel analyzer and integrator, and store and display the energy spectrum and integration data.

[0015] Optionally, the charge-sensitive preamplifier is integrated with a hemispherical CdZnTe detector to convert the charge generated by the hemispherical CdZnTe detector absorbing hard X-rays into a voltage signal.

[0016] Optionally, the digital multi-channel analyzer and integrator adopts a multi-channel board structure design based on a PXI e chassis, and also includes an FPGA for receiving the data stream output by the ADC, realizing multi-channel analysis and integration processing, and communicating with the main controller.

[0017] Optionally, the acquisition and control software includes a storage and display module for energy spectrum and integral data and a system parameter setting module;

[0018] The storage and display module of energy spectrum and integral data includes the setting of channel address number (256-4096 optional), time sharing time, upper threshold limit, lower threshold limit, ten-fold attenuation, whether to collect negative signals, and data preservation;

[0019] The system parameter setting module includes setting the data sending frequency, integration time and data storage; obtaining the gun number and discharge duration from the Tokamak central control system through a UDP connection, automatically collecting and saving data after receiving the trigger, and realizing real-time display of data.

[0020] Optionally, the hemispherical CdZnTe detector is provided with an electromagnetic shielding layer and a radiation shielding body on the outside, the electromagnetic shielding layer is made of aluminum or copper, and the protective shell is made of radiation-resistant material, so as to improve the durability and stability of the detector.

[0021] Optionally, the digital multi-channel analyzer and integrator board is provided with indicator lights for displaying working status and fault conditions.

[0022] Optionally, the system further comprises a heat dissipation device connected to the digital multi-channel analyzer and the integrator for dissipating heat generated during operation to ensure stable operation of the system.

[0023] Compared with the prior art, the present invention has at least one of the following beneficial technical effects:

[0024] The system of the present invention is compact, simplifies the existing hard X-ray energy spectrum and flux measurement system, is conducive to the installation of more detectors and acquisition systems on the tokamak, thereby improving the spatial resolution of hard X-ray diagnosis, and at the same time, the system has a high degree of integration, high system maintainability and high maintenance efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A block diagram of a digital energy spectrum and flux system for tokamak hard X-ray measurement;

[0026] Figure 2 It is the block diagram of digital multi-channel analyzer and integrator;

[0027] Figure 3 This is a physical picture of the digital multi-channel analyzer and integrator plug-in;

[0028] Figure 4 Set up the interface for acquisition and control software. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] like Figure 1 As shown, the digital energy spectrum and flux system for tokamak hard X-ray measurement proposed by the present invention includes a hemispherical cadmium zinc telluride detector for receiving hard X-rays generated by fast electrons in plasma and ionizing them to generate charges; a hemispherical CZT detector with a detector size of 5mm*5mm*2.5mm and a hard X-ray measurement range of 20keV-700keV. The CZT detector has the advantages of high energy resolution, resistance to magnetic field interference, and operation at room temperature, and is very suitable for working in the complex electromagnetic environment of the tokamak.

[0032] In this embodiment, a charge-sensitive preamplifier is also included, which is connected to the hemispherical cadmium zinc telluride detector and is used to convert the charge generated by the detector into a voltage signal; the charge-sensitive preamplifier is used to convert the charge generated by the CZT detector absorbing hard X-rays into a voltage signal. The preamplifier gain G = 10mV / fC, the falling edge time is 200μs-300μs, and the preamplifier is integrated with the CZT detector to reduce noise.

[0033] The shaping amplifier is connected to the charge sensitive preamplifier to shape and amplify the voltage signal; the shaping amplifier is used to shape and amplify the signal from the charge sensitive preamplifier. The shaping amplifier has an adjustable gain of 1-200, a shaping time of 0.3μs-3μs, a filter type of CR-RC2, and an output impedance of 50Ω.

[0034] In addition, it also includes a digital multi-channel analyzer and integrator, which is connected to the shaping amplifier to perform multi-channel analysis and digital integration; the digital multi-channel analyzer and integrator are used to perform multi-channel processing and integration processing on the signal from the shaping amplifier, and then upload it to the main controller. The digital multi-channel analyzer and integrator adopt a multi-channel board structure design based on the PXI e chassis. The FPGA, as the digital processing core, is responsible for receiving the data stream output by the ADC, realizing multi-channel analysis and integration processing, and communicating with the main controller. The digital multi-channel analyzer and integrator adopt a PXI e network communication mode and run in the PXI e chassis. Each multi-channel analyzer and integrator plug-in adopts 4-channel analog input and 1 hardware trigger input; the analog signal input range is -1V-+1V or -10V-+10V optional; the sampling rate is 20Msps16bit. Among them, the maximum Dow of the multi-channel analyzer is 4096; the fastest time resolution is 1ms; the integrator integration time is 100μs-2ms, and the integration data generation frequency is 20kHz-500kHz. One PXI e chassis can support five multi-channel analyzer and integrator plug-ins and data acquisition for 20 CZT detectors.

[0035] Furthermore, this embodiment is also provided with an acquisition and control software installed on the host computer, which is used to receive signals from the digital multi-channel analyzer and integrator, and store and display the energy spectrum and integral data. The acquisition and control software includes a storage and display module for energy spectrum and integral data and a system parameter setting module; the acquisition and control software is developed based on the open source software QT. The data of the digital multi-channel analyzer and integrator are transmitted to the main controller through the PXI e bus, and the main controller is connected to the high-speed data interaction network (DAN) to transmit the data to the EPI CS central controller to store and display the energy spectrum and integral data. The functions of energy spectrum acquisition include setting the number of channel addresses (256-4096 optional), time-sharing time, upper threshold limit, lower threshold limit, ten-fold attenuation, whether to collect negative signals, and data preservation; the functions of digital integration include setting the data sending frequency, integration time size and data preservation. In order to meet the needs of tokamak plasma physics experiments, the gun number and discharge duration are obtained from the tokamak central control system through a udp connection, and data is automatically collected and saved after receiving the trigger, and real-time display of data is realized at the same time.

[0036] In this embodiment, the charge sensitive preamplifier is integrated with the hemispherical CdZnTe detector to convert the charge generated by the hemispherical CdZnTe detector absorbing hard X-rays into a voltage signal.

[0037] like Figure 2 - Figure 3 As shown, the signal of the shaping amplifier first enters the ADC for analog-to-digital conversion, then enters the FPGA for multi-channel analysis and digital integration, and then transmits the data to the host computer through the main controller. The digital multi-channel analyzer and integrator also need to receive a trigger signal and start working after receiving the trigger signal.

[0038] like Figure 4 The following is the interface for setting the acquisition and control software. The functions of spectrum acquisition include setting the number of channel addresses (256-4096 optional), time sharing time, upper threshold, lower threshold, ten-fold attenuation, whether to collect negative signals, and data saving; the functions of digital integration include setting the data transmission frequency, integration time, and data saving. The acquisition and control software obtains the gun number and discharge duration from the Tokamak central control system through a UDP connection. After receiving the trigger, it automatically collects and saves the data, and realizes real-time display of the data. After the discharge duration is reached, the system stops collecting data.

[0039] Before the system is put into use, it is necessary to use a radioactive source for energy calibration. Generally, a 152Eu radioactive source is used, and the energy calibration can be performed using four characteristic spectrometers of the 152Eu radioactive source: 40keV, 121keV, 244keV, and 344keV. After the system is calibrated, hard X-ray energy spectrum and flux measurements can be performed.

[0040] Example 2

[0041] In this embodiment, based on the first embodiment, the hemispherical cadmium zinc telluride detector is provided with a protective shell on the outside, and the protective shell is made of radiation-resistant material to improve the durability and stability of the detector. The board of the digital multi-channel analyzer and integrator is provided with an indicator light for displaying the working status and fault conditions. The system also includes a heat dissipation device connected to the digital multi-channel analyzer and integrator to dissipate the heat generated during the working process to ensure the stable operation of the system.

[0042] The above specific embodiments are only several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A digital energy spectrum and flux system for tokamak hard X-ray measurement, characterized in that: include: Hemispherical CdZnTe detector, used to receive hard X-rays generated by fast electrons in plasma and ionize them to generate charges; A charge-sensitive preamplifier connected to the hemispherical cadmium zinc telluride detector and used for converting the charge generated by the detector into a voltage signal; a shaping amplifier connected to the charge sensitive preamplifier to shape and amplify the voltage signal; A digital multi-channel analyzer and integrator, connected to the shaping amplifier, performs multi-channel analysis and digital integration; The acquisition and control software installed on the host computer is used to receive signals from the digital multi-channel analyzer and integrator, and store and display the energy spectrum and integration data.

2. A digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: The charge sensitive preamplifier is integrated with a hemispherical cadmium zinc telluride detector.

3. The digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: The digital multi-channel analyzer and integrator adopts a multi-channel board structure design based on a PXIe chassis, and also includes an FPGA for receiving the data stream output by the ADC, realizing multi-channel analysis and integration processing, and communicating with the main controller.

4. The digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: The acquisition and control software includes a storage and display module for energy spectrum and integral data and a system parameter setting module; The storage and display module of energy spectrum and integral data includes the setting of channel number, time sharing time, upper threshold, lower threshold, ten-fold attenuation, whether to collect negative signals, and data preservation; The system parameter setting module includes setting the data sending frequency, integration time and data saving.

5. The digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: An electromagnetic shielding layer and a radiation shielding body are arranged outside the hemispherical CdZnTe detector.

6. The digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: The boards of the digital multi-channel analyzer and integrator are provided with indicator lights for displaying working status and fault conditions.

7. The digital energy spectrum and flux system for tokamak hard X-ray measurement according to claim 1, characterized in that: The system also includes a heat sink connected to the digital multi-channel analyzer and the integrator.

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