An X-ray imaging diagnostic system based on Timepix3 detector

Abstract

The present invention discloses an X-ray imaging diagnostic system based on a Timepix3 detector, belonging to the field of plasma diagnostic technology. The system includes a Timepix3 detector, a data server, a host computer, a signal generator, and a high-voltage power supply. The signal generator is used to remotely control the Timepix3 detector, providing pulses during plasma discharge to ensure that the Timepix3 detector collects data in trigger mode. The high-voltage power supply is used to provide a bias voltage for the semiconductor sensor of the Timepix3 detector. The host computer is used to send instructions to the Timepix3 detector for data collection. The data server is used to receive and save the collected data. The present invention can be applied to plasma discharge experiments conducted in tokamaks, and has higher spatial resolution, stronger temporal resolution, and the ability to quickly obtain X-ray signal energy spectra.

Description

Technical Field

[0001] The present invention belongs to the technical field of plasma diagnosis, and in particular relates to an X-ray imaging diagnostic system based on a Timepix3 detector. Background Art

[0002] Radiation generated during plasma discharge reflects changes in electron density, temperature, and impurity levels, and the radiation signal can be transmitted unattenuated outside the plasma. Therefore, plasma radiation measurement is an effective method for diagnosing many plasma parameters. Currently, the radiation signal measurement systems used in the Experimental Advanced Superconducting Tokamak (EAST) are mostly detector arrays. Array systems composed of multiple detectors offer numerous advantages, including a simple structure, strong anti-interference capabilities, and overall system reliability and stability. However, they are somewhat inferior in spatial resolution and rapid acquisition of energy spectra. The Timepix3 detector, on the other hand, features multiple operating modes, including counting and threshold-crossing time modes, and event-driven capabilities. It can obtain information such as the number of X-rays, the energy of each X-ray, and the arrival time. This makes it possible to determine the spatial distribution of X-rays and rapidly acquire energy spectra. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides an X-ray imaging diagnostic system based on the Timepix3 detector, which can obtain the time evolution law and energy spectrum information of the radiation signal intensity, as well as the spatial distribution information of the radiation signal intensity at different times in the plasma discharge experiment in the tokamak device.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] An X-ray imaging diagnostic system based on a Timepix3 detector, the system comprising a Timepix3 detector, a data server, a host computer, a signal generator, and a high-voltage power supply; wherein,

[0006] The signal generator is used to remotely control the Timepix3 detector and provide pulses during plasma discharge to ensure that the Timepix3 detector collects data in trigger mode;

[0007] The high voltage power supply is used to provide a bias voltage for the semiconductor sensor of the Timepix3 detector;

[0008] The host computer is used to send instructions to the Timepix3 detector to collect data;

[0009] The data server is used to receive and save the collected data.

[0010] Furthermore, the Timepix3 detector includes a semiconductor sensor and a Timepix3 readout chip, each pixel works independently, and each detected photon event is saved in the form of raw data.

[0011] Furthermore, when the Timepix3 detector operates in counting mode, it is used to obtain an image containing information on the count value of each pixel. The evolution law of the X-ray signal intensity over time is obtained by calculating the count values ​​of all pixels within the exposure time of each frame of the image, and the spatial distribution information of the X-ray signal is obtained by analyzing the size of the pixel count values ​​at different positions.

[0012] Furthermore, the Timepix3 detector is used to obtain images and raw data containing energy information of each photon event when operating in the over-threshold time mode, and obtain the energy spectrum of the X-ray signal by analyzing the energy information of all detected photons.

[0013] Furthermore, a metal protective box is provided outside the Timepix3 detector. The metal protective box uses four lead plates to cover the upper, lower, left and right sides of the rectangular Timepix3 detector respectively, and uses a tungsten plate to cover the front end face where the semiconductor sensor of the Timepix3 detector is located. The four lead plates and one tungsten plate are wrapped and fixed with five 316L stainless steel plates on the outside.

[0014] Furthermore, a conical hole is opened in the center of the tungsten plate, the circular surface of the conical hole faces the Timepix3 detector, and the conical surface faces outward along the central axis of the tungsten plate to cover the sensitive area of ​​the sensor end of the Timepix3 detector.

[0015] The beneficial effects of the present invention are:

[0016] The Timepix3 detector is innovatively applied to the imaging diagnostic system, which has two operating modes. When operating in counting mode, the Timepix3 detector can obtain an image containing the number of detected X-ray photons. By calculating the number of X-ray photons detected during the image exposure time, the relative X-ray intensity at a certain point in time is obtained. The temporal evolution of the X-ray intensity is obtained based on the change in the number of X-ray photons in the image, and the spatial distribution information of the X-rays is obtained based on the number of photons detected at pixels at different positions. When operating in over-threshold time mode, the Timepix3 detector can obtain an image containing X-ray photon energy information. By counting the number of photons of different energies in the image, the X-ray energy spectrum can be obtained. Compared with traditional detection array systems, the Timepix3 imaging diagnostic system has higher spatial resolution, stronger temporal resolution, and the ability to quickly obtain the energy spectrum of X-ray signals. In addition, a metal protective box is designed for the Timepix3 detector to ensure that the Timepix3 detector can operate in a radiation environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of an X-ray imaging diagnostic system based on the Timepix3 detector of the present invention;

[0018] Figure 2 This is a view of the field of view and top view of an X-ray imaging diagnostic system based on the Timepix3 detector of the present invention;

[0019] Figure 3 This is the structural diagram of the metal protection box;

[0020] Figure 4 Schematic diagram of the tapered hole position;

[0021] Figure 5 This is the working principle diagram of the detector in counting mode;

[0022] Figure 6 Flowchart for obtaining the time evolution information of X-ray signal intensity in detector counting mode;

[0023] Figure 7 is the evolution of X-ray signal intensity over time;

[0024] Figure 8 This is the working principle diagram of the detector in the threshold time mode;

[0025] Figure 9 Flowchart for obtaining X-ray energy spectrum in detector over-threshold time mode;

[0026] Figure 10 This is the image collected in the detector's over-threshold time mode;

[0027] Figure 11 for 152 Cluster volume histogram of Eu.

[0028] Reference numerals:

[0029] 1. Timepix3 detector, 2. Copper bracket, 3. Lead plate, 4. Tungsten plate, 5. 316L stainless steel plate. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and examples.

[0031] like Figure 1 As shown, the X-ray imaging diagnostic system based on the Timepix3 detector consists of three parts: the Timepix3 detector 1, a data server, and a host computer. The Timepix3 detector 1 requires a high-voltage power supply and a signal generator. The signal generator can remotely control the Timepix3 detector 1 through a built-in webpage, providing pulses during plasma discharge to ensure that the Timepix3 detector 1 can normally collect data in trigger mode. The high-voltage power supply provides a bias voltage of -200V to -300V for the semiconductor sensor of the Timepix3 detector 1. When X-ray photons hit the semiconductor sensor, an electric charge is generated. The bias voltage can reduce the drift time of the charge and inhibit the diffusion of the charge in adjacent pixels. In the control room, the user uses the host computer to send instructions to the Timepix3 detector 1 to collect and save data. The collected data is transmitted to the data server via optical fiber for storage.

[0032] The Timepix3 detector 1 is composed of a semiconductor sensor and a Timepix3 readout chip. The sensor material used is 1mm cadmium telluride, which has a high efficiency in detecting photons in the soft X-ray energy range. The Timepix3 detector 1 has event-driven capabilities, that is, each pixel can work independently and save each detected photon event in the form of raw data.

[0033] like Figure 2 As shown in the figure, a metal protection box is designed for the Timepix3 detector to shield the radiation generated during the plasma discharge process, ensuring that the Timepix3 detector can operate in a radiation environment. The Timepix3 detector 1 and the metal protection box are placed in the F window of the EAST device to observe the middle and lower part of the cross-section of the EAST vacuum chamber. Analysis shows that the field of view of the system of the present invention is ±16°, the image distance is 35mm, the object distance is 2500mm, and the spatial resolution is below 10mm:

[0034] = =

[0035] in is the spatial resolution, is the distance between pixels of Timepix3 detector 1, is the object distance, For distance.

[0036] like Figure 3 As shown in the figure, a schematic diagram of the specific structural design of the metal protection box is given. The Timepix3 detector 1 is a rectangular parallelepiped structure, including 6 end faces in total, namely, top, bottom, left, right, front and back. Among them, the lower end face is supported by a copper bracket 2 to facilitate heat conduction. The sensor end of the Timepix3 detector 1 is the front end face, which is covered with a tungsten plate 4 with a thickness of 15 mm. A conical hole with a diameter of 0.3 mm and an angle of 32° is opened in the center of the tungsten plate 4. The conical hole is opposite to the sensor end of the Timepix3 detector 1 to ensure that the imaging surface covers the sensitive area of ​​the Timepix3 detector 1. Ideally, only rays within the field of view of the small hole (such as Figure 2 Only rays (as shown) can pass through the pinhole and enter the Timepix3 detector 1. Rays outside the field of view are blocked by the metal protective box. With the object distance fixed, spatial resolution can be adjusted by varying the pinhole diameter and image distance. The top, bottom, left, and right end faces of the Timepix3 detector 1 are covered with lead plates 3. The lead plate 3 on the lower end face is positioned beneath the copper bracket 2 to fully enclose the Timepix3 detector 1. The tungsten plate 4 and the four lead plates 3 are then encased in a 316L stainless steel plate 5, ultimately securing the double-layered metal protective box.

[0037] like Figure 4 As shown, a conical hole is opened in the center of the tungsten plate 4, with the circular surface of the conical hole facing the Timepix3 detector and the conical surface facing outward along the central axis of the tungsten plate, ensuring that the light incident from the conical hole completely covers the sensitive area of ​​the sensor end of the Timepix3 detector 1.

[0038] like Figure 5 As shown, the Timepix3 detector 1 has a counting mode, the basic operating mode of a photon counting detector. X-rays interact with semiconductors to generate electron-hole pairs, which are collected and processed by subsequent circuitry. During the shutter time, if the intensity of the charge signal exceeds a set threshold, the pixel counter increments by one, indicating that a photon with energy above the threshold has been detected. Otherwise, no count is recorded.

[0039] like Figure 6-Figure 7 As shown, Figure 6 This is a flow chart for obtaining the time evolution information of X-ray signal intensity in detector counting mode. Figure 7This is a graph showing the evolution of X-ray signal intensity over time. The Timepix3 detector 1 acquires images in counting mode and calculates the pixel count values ​​of the images at different time points to obtain the time evolution information of the X-ray signal. The count value represents the relative intensity of the X-ray signal.

[0040] like Figure 8 As shown, the Timepix3 detector 1 features a Time-over-Threshold (ToT) mode. In this mode, a counter starts when the signal exceeds the set threshold and stops when the signal strength drops back below the threshold. If multiple consecutive signals exceed the threshold with the same shutter time, the counts are accumulated. Because the time above the threshold is proportional to the input charge, ToT provides a direct estimate of the integrated energy over the shutter duration. The measurement result is the total charge collected by a single pixel.

[0041] like Figure 9 As shown, the detector acquires data in over-threshold time mode and controls the exposure time to ensure that pixel clusters in the acquired image do not overlap. For each frame, all pixel clusters in the image are searched and classified by area size. The sum of all pixel counts in each cluster (the cluster volume) is calculated, and histograms of the volume of clusters of different areas are plotted according to area size to obtain the X-ray energy spectrum.

[0042] like Figure 10 As shown, it can be observed that all the energy of some photons is deposited in one detector pixel, which appears as a single independent pixel in the figure, while some photons deposit energy in multiple detector pixels, which appears as multiple adjacent pixels (a pixel cluster) in the figure.

[0043] like Figure 11 As shown in the figure, in over-threshold time mode, the measured energy spectrum is often counted by cluster area. All pixel counts within each cluster are summed to obtain n values ​​(cluster volume). The statistical histogram of these n values ​​is the energy spectrum. Different cluster areas correspond to different energy spectra. A larger cluster volume indicates greater detected photon energy. All area clusters include the first, second, third, and fourth area clusters.

[0044] Radiation generated during a plasma discharge reflects changes in electron density, temperature, and impurity levels, and the radiation signal can be transmitted to the plasma without attenuation. A Timepix3-based X-ray diagnostic system can capture information such as the temporal evolution, spatial distribution, and energy spectrum of the radiation signal. By analyzing the acquired signals, various plasma parameters can be diagnosed.

[0045] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are 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 in the scope of protection of the present invention.

Claims

1. An X-ray imaging diagnostic system based on the Timepix3 detector, characterized in that: The system includes a Timepix3 detector, a data server, a host computer, a signal generator, and a high-voltage power supply; wherein, The signal generator is used to remotely control the Timepix3 detector and provide pulses during plasma discharge to ensure that the Timepix3 detector collects data in trigger mode; The high voltage power supply is used to provide a bias voltage for the semiconductor sensor of the Timepix3 detector; The host computer is used to send instructions to the Timepix3 detector to collect data; The data server is used to receive and save the collected data; Among them, when the Timepix3 detector works in counting mode, it is used to obtain an image containing the count value information of each pixel, obtain the evolution law of the X-ray signal intensity over time by calculating all pixel count values ​​within the exposure time of each frame of image, and obtain the spatial distribution information of the X-ray signal by analyzing the size of the pixel count values ​​at different positions; when the Timepix3 detector works in over-threshold time mode, it is used to obtain images and raw data containing the energy information of each photon event, and obtain the energy spectrum of the X-ray signal by analyzing the energy information of all detected photons.

2. The X-ray imaging diagnostic system based on the Timepix3 detector according to claim 1, characterized in that: The Timepix3 detector includes a semiconductor sensor and a Timepix3 readout chip. Each pixel works independently and saves each detected photon event in the form of raw data.

3. The X-ray imaging diagnostic system based on the Timepix3 detector according to claim 1, characterized in that: A metal protective box is provided outside the Timepix3 detector. The metal protective box uses four lead plates to cover the upper, lower, left and right sides of the rectangular Timepix3 detector respectively, and uses a tungsten plate to cover the front end face where the semiconductor sensor of the Timepix3 detector is located. The four lead plates and one tungsten plate are wrapped and fixed with five 316L stainless steel plates.

4. The X-ray imaging diagnostic system based on the Timepix3 detector according to claim 3, characterized in that: A conical hole is opened in the center of the tungsten plate, the circular surface of the conical hole faces the Timepix3 detector, and the conical surface faces outward along the central axis of the tungsten plate to cover the sensitive area of ​​the sensor end of the Timepix3 detector.

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