基于脉冲星导航的MCP空间X射线探测器关键技术的研究
发布时间：2018-08-24 18:26
【摘要】：随着航天技术的发展，传统的卫星导航系统越来越不能满足需求，在功能上呈现出一定的局限性。为了打破这一局限，近些年各航天大国对下一代导航系统—X射线脉冲星导航系统，投入了大量的人力、物力资源进行研究。本文在调研国内外探测器研究与应用发展的基础上，对应用于X射线脉冲星导航系统的探测器性能需求进行了分析，并重点研究了用于导航的MCP空间X射线探测器。 在进行X射线脉冲星导航空间搭载试验和未来脉冲星导航系统实际应用之前，必须在地面搭建实验模拟系统，对探测器进行全面的实验测试与标定，例如量子效率、探测效率、光子到达时间精度、脉冲轮廓的累积时间、定位精度等的计算。要标定探测器首先要有一个已知光子流量的X射线源，并且该射线源的能谱具有良好的单色性。此外，X射线源的光子流量可以根据测试需求进行调节。根据实验需求，对课题组研制的用于标定测试探测器的X射线源。该X射线源能够产生七个单色能量的射线，分别是1.49keV、4.51keV、5.41keV、6.4keV、8.05keV、15.77keV、17.48keV。在真空环境下，用SDD探测器测试标定了X射线源的最佳预热时间、光子流量稳定度、能谱分布、模拟脉冲轮廓特性，并通过改变X射线源到探测器的距离、灯丝电流和阳极高压，对每一个能量下的X射线光子流量进行了测试标定，为后续探测器的探测效率的测试标定奠定了基础。 关于MCP探测器的研究本文重点从两个方面进行了研究： 一、为了提高探测器的探测效率，设计了复合式光电阴极结构，主要工作内容如下所述： 在对复合式光电阴极进行实验测试之前，仿真计算出探测器正常工作时的两个电压的最优值：（1）采用CST软件模拟计算出阴极电压和MCP输入电压的电势差在-300V时工作最佳；（2）为了提高探测器探测效率和探测的可靠性，优化了收集阳极电压V1。提高探测器收集阳极电压可以减小电子云团的直径，，降低电子云团发生交叠的概率，阳极电压越高，电子云团的直径就越小，小到一定的尺寸后将不会变。通过计算可以得到电子云团入射到收集阳极上时的半径，计算结果显示：当收集阳极电压在0V时，将电子云团的半径约为0.9mm；当收集阳极电压在-450V时，电子云团的半径为0.6mm，继续增大收集阳极电压至-800V，电子云团的半径变化很小，仍然约为0.6mm。根据这一计算结果可以确定收集阳极电压-450V时最佳。（3）对复合式光电阴极的透射层碘化铯的最佳厚度采用两种计算方法进行计算，第一种是1981年汉克推导的计算模型，第二种是2011年胡慧君博士论文中推导出的计算模型，计算结果显示，两种算法下的最佳厚度值有一定的偏差。为了确定哪种计算方法可靠，用GEANT4软件对不同厚度下的透射层碘化铯的量子效率和探测效率进行模拟计算，通过模拟实验获知：采用第二种算法得出的厚度值是最佳的；为了进一步确认第二种算法的可靠性，计算光子能量一定时，不同厚度的透射层碘化铯阴极的量子效率和探测效率，计算结果表明，第二种计算方法得出的最佳厚度值是可靠的。 为验证复合式光电阴极是否能够有效的提高探测器的探测效率，制备了纯反射式光电阴极和复合式光电阴极，并测试它们的探测效率。测试结果显示：在相同的实验条件下，复合式光电阴极的探测效率要高于纯反射式光电阴极，分别可达到25.2%@1.49keV（透射层79.9nm+反射层1000nm）、14.2%@4.51keV（透射层144.35nm+反射层1000nm），而纯反射光电阴极在相同的实验条件下的探测效率分别16.2%@1.49keV（1079.9nm）、10.1%@4.51keV（1144.35nm）。 二、为了增大探测器的面积，初步对2×2阵列探测器进行研究，重点是多通道共享阳极的研究。 首先，依据航天探测器设计的基本原则设计了2×2阵列的X射线探测器雏形用于实验研究，并对各个零件进行了选材工作。此外，从两个方面对2×2阵列探测器进行了优化。 （1）提出了一种甄选性能一致的MCP的方法，该方法包括确立4个甄选关键参数、建立MCP可用标准、优化实验测试流程和实验测试四个过程。 （2）研制出多通道共享阳极，通过减少读出电子学通道数以降低大面阵MCP探测器电子学采集系统的成本、重量和功耗。分别对单通道阳极、双通道共享阳极、和四通道共享阳极的脉冲信号传输性能进行了模拟，模拟结果显示这三种阳极在传输频率低于0.1GHz的脉冲信号时波形无畸变、幅值无衰减、脉冲宽度无展宽，与实验中用示波器观察得到的结果相吻合。实验表明：可以使用一个收集阳极和一路电子学来接收四个通道的信号，这样使得探测器的电子学通道数目减少到原来的1/4，可以大大减小电子学系统的成本、重量和功耗。
[Abstract]:With the development of space technology, the traditional satellite navigation system can not meet the demand more and more, and has some limitations in function. In order to break this limitation, in recent years, the space powers have invested a lot of manpower and material resources in the next generation of navigation system-X-ray pulsar navigation system. On the basis of the research and application development of the external detectors, the performance requirements of the detectors used in the X-ray pulsar navigation system are analyzed, and the MCP space X-ray detectors used for navigation are mainly studied.
Before carrying out the space test of X-ray pulsar navigation and the practical application of future pulsar navigation system, it is necessary to build an experimental simulation system on the ground to test and calibrate the detector comprehensively, such as quantum efficiency, detection efficiency, photon arrival time accuracy, pulse profile accumulation time, positioning accuracy and so on. In order to calibrate the detector, we must first have an X-ray source with known photon flux, and the energy spectrum of the source has good monochromaticity. In addition, the photon flux of the X-ray source can be adjusted according to the test requirements. The optimum preheating time, photon flux stability, energy spectrum distribution, pulse profile characteristics of the X-ray source were calibrated by SDD detector in vacuum. The distance from the X-ray source to the detector, filament current and positive current were changed. The X-ray photon flux at each energy was measured and calibrated under extreme high pressure, which laid a foundation for the subsequent detection efficiency test and calibration of the detector.
The research on MCP detector is focused on two aspects:
First, in order to improve the detection efficiency of the detector, a composite photocathode structure is designed. The main work is as follows:
Before testing the composite photocathode, the optimal values of the two voltages in the normal operation of the detector are calculated by simulation: (1) the potential difference between the cathode voltage and the MCP input voltage is calculated by CST software, which works best at - 300V; (2) in order to improve the detection efficiency and reliability of the detector, the collecting anode is optimized. The higher the anode voltage is, the smaller the diameter of the electron cloud will be, and it will not change when it reaches a certain size. When the anode voltage is 0 V, the radius of the electron cloud is about 0.9 mm; when the anode voltage is - 450 V, the radius of the electron cloud is 0.6 mm; when the anode voltage is - 450 V, the collection anode voltage continues to increase to - 800 V, the radius of the electron cloud changes very little, still about 0.6 mm. The optimum thickness of the transmission layer of compound photocathode cesium iodide is calculated by two methods. The first one is the calculation model deduced by Hank in 1981 and the second one is the calculation model deduced by Hu Huijun in his dissertation in 2011. The calculation results show that there is a certain deviation between the two methods. The quantum efficiency and detection efficiency of the transmission layer of cesium iodide with different thickness are simulated by GEANT4 software. The simulation results show that the thickness obtained by the second algorithm is the best; in order to further confirm the reliability of the second algorithm, when the photon energy is fixed, the thickness of the different thickness is calculated. The quantum efficiency and detection efficiency of the transmission layer cesium iodide cathode show that the optimum thickness obtained by the second method is reliable.
Pure reflection photocathode and composite photocathode were fabricated to verify whether the composite photocathode can effectively improve the detection efficiency of the detector, and their detection efficiency was tested. The detection efficiency of pure reflection photocathode is 16.2%@1.49 keV (1079.9 nm) and 10.1%@4.51 keV (1144.35 nm) respectively.
Secondly, in order to increase the area of the detector, the 2 *2 array detector is preliminarily studied, with the emphasis on the study of multi-channel shared anode.
Firstly, according to the basic principle of spacecraft detector design, the prototype of 2 *2 array X-ray detector is designed for experimental research, and the material selection of each part is carried out. In addition, the 2 *2 array detector is optimized from two aspects.
(1) A method of selecting MCP with uniform performance is proposed. The method consists of four steps: establishing four key parameters, establishing available standards of MCP, optimizing experimental testing process and testing process.
(2) A multi-channel shared anode is developed to reduce the cost, weight and power consumption of the electronic acquisition system for large area array MCP detectors by reducing the number of readout electronics channels. The waveform of the pulse signal with transmission frequency less than 0.1 GHz is not distorted, the amplitude is not attenuated, and the pulse width is not broadened, which is consistent with the experimental results obtained by oscilloscope observation. The experiment shows that a collector anode and a circuit electronics can be used to receive the signals of the four channels, thus reducing the number of electronic channels of the detector to less than 0.1 GHz. The original 1/4 can greatly reduce the cost, weight and power consumption of the electronics system.
【学位授予单位】：中国科学院研究生院（西安光学精密机械研究所）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN966
本文编号：2201662
[Abstract]:With the development of space technology, the traditional satellite navigation system can not meet the demand more and more, and has some limitations in function. In order to break this limitation, in recent years, the space powers have invested a lot of manpower and material resources in the next generation of navigation system-X-ray pulsar navigation system. On the basis of the research and application development of the external detectors, the performance requirements of the detectors used in the X-ray pulsar navigation system are analyzed, and the MCP space X-ray detectors used for navigation are mainly studied.
Before carrying out the space test of X-ray pulsar navigation and the practical application of future pulsar navigation system, it is necessary to build an experimental simulation system on the ground to test and calibrate the detector comprehensively, such as quantum efficiency, detection efficiency, photon arrival time accuracy, pulse profile accumulation time, positioning accuracy and so on. In order to calibrate the detector, we must first have an X-ray source with known photon flux, and the energy spectrum of the source has good monochromaticity. In addition, the photon flux of the X-ray source can be adjusted according to the test requirements. The optimum preheating time, photon flux stability, energy spectrum distribution, pulse profile characteristics of the X-ray source were calibrated by SDD detector in vacuum. The distance from the X-ray source to the detector, filament current and positive current were changed. The X-ray photon flux at each energy was measured and calibrated under extreme high pressure, which laid a foundation for the subsequent detection efficiency test and calibration of the detector.
The research on MCP detector is focused on two aspects:
First, in order to improve the detection efficiency of the detector, a composite photocathode structure is designed. The main work is as follows:
Before testing the composite photocathode, the optimal values of the two voltages in the normal operation of the detector are calculated by simulation: (1) the potential difference between the cathode voltage and the MCP input voltage is calculated by CST software, which works best at - 300V; (2) in order to improve the detection efficiency and reliability of the detector, the collecting anode is optimized. The higher the anode voltage is, the smaller the diameter of the electron cloud will be, and it will not change when it reaches a certain size. When the anode voltage is 0 V, the radius of the electron cloud is about 0.9 mm; when the anode voltage is - 450 V, the radius of the electron cloud is 0.6 mm; when the anode voltage is - 450 V, the collection anode voltage continues to increase to - 800 V, the radius of the electron cloud changes very little, still about 0.6 mm. The optimum thickness of the transmission layer of compound photocathode cesium iodide is calculated by two methods. The first one is the calculation model deduced by Hank in 1981 and the second one is the calculation model deduced by Hu Huijun in his dissertation in 2011. The calculation results show that there is a certain deviation between the two methods. The quantum efficiency and detection efficiency of the transmission layer of cesium iodide with different thickness are simulated by GEANT4 software. The simulation results show that the thickness obtained by the second algorithm is the best; in order to further confirm the reliability of the second algorithm, when the photon energy is fixed, the thickness of the different thickness is calculated. The quantum efficiency and detection efficiency of the transmission layer cesium iodide cathode show that the optimum thickness obtained by the second method is reliable.
Pure reflection photocathode and composite photocathode were fabricated to verify whether the composite photocathode can effectively improve the detection efficiency of the detector, and their detection efficiency was tested. The detection efficiency of pure reflection photocathode is 16.2%@1.49 keV (1079.9 nm) and 10.1%@4.51 keV (1144.35 nm) respectively.
Secondly, in order to increase the area of the detector, the 2 *2 array detector is preliminarily studied, with the emphasis on the study of multi-channel shared anode.
Firstly, according to the basic principle of spacecraft detector design, the prototype of 2 *2 array X-ray detector is designed for experimental research, and the material selection of each part is carried out. In addition, the 2 *2 array detector is optimized from two aspects.
(1) A method of selecting MCP with uniform performance is proposed. The method consists of four steps: establishing four key parameters, establishing available standards of MCP, optimizing experimental testing process and testing process.
(2) A multi-channel shared anode is developed to reduce the cost, weight and power consumption of the electronic acquisition system for large area array MCP detectors by reducing the number of readout electronics channels. The waveform of the pulse signal with transmission frequency less than 0.1 GHz is not distorted, the amplitude is not attenuated, and the pulse width is not broadened, which is consistent with the experimental results obtained by oscilloscope observation. The experiment shows that a collector anode and a circuit electronics can be used to receive the signals of the four channels, thus reducing the number of electronic channels of the detector to less than 0.1 GHz. The original 1/4 can greatly reduce the cost, weight and power consumption of the electronics system.
【学位授予单位】：中国科学院研究生院（西安光学精密机械研究所）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN966
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