数字化波形采样技术在粒子探测中的应用与研究

发布时间：2018-04-02 07:33

本文选题：波形采样　切入点：数字波形分析　出处：《中国科学院研究生院(近代物理研究所)》2016年博士论文

【摘要】：正电子发射断层成像(Positron Emission Tomography,PET)可以实现对重离子束辐照剂量分布与定位的监测,在PET中引入飞行时间信息(Time of Flight,TOF)可以减少图像重建时的数据处理时间,改善影像质量。在研制应用于重离子治癌监测的TOF-PET系统时,传统的分立式的电子学读出系统因规模庞大、电路复杂、功耗高、测量精度低以及可靠性差等问题,无法满足TOF-PET系统的需求。因此,需要设计开发新的低成本,高集成度的读出电子学系统。基于这一需求,我们与核电子学研究组合作开发了以基于SCA(Switched Capacitor Array)的DRS4芯片(Dumino Ring Sampler version 4)为核心的数字化波形采样系统,在级联工作模式下可以同时对16路信号进行采样,具有On-Board符合测量的功能,可以实现TOF信息的测量以及能量的测量。本文通过对基于LaBr3晶体的TOF-PET定时校准系统输出脉冲进行数字化波形采样以及数据采集,开展了基于DRS4芯片的数字化波形采样系统的应用以及后续数据处理方法的研究。实验结果表明,利用DRS4系统以及数字化波形分析算法,TOF-PET定时校准系统获得了很好的符合时间分辨(178 ps)和能量分辨(3.42%@511 keV),优于进行对比测试的CAMAC系统获得的符合时间分辨(250ps)以及能量分辨(4.2%@511 keV)。成功研制了由LaBr3晶体阵列、位置灵敏型的光电倍增管及简化的读出电路组成的TOF-PET单元样机。在国内首次利用DRS4系统对样机进行了On-Board符合测试,使用数字化算法对采样数据进行分析。相比CAMAC系统,使用DRS4系统得到的晶体位置映射图更加清晰且易于分割,信噪比更高。DRS4系统获得了较好的能量分辨(14.9%)位置分辨(0.74mm)和符合时间分辨(750 ps),验证了DRS4系统在TOF-PET中应用的可行性,实现了预期目标。我们在国内首次利用DRS4系统在原子核能级寿命测量以及在束粒子鉴别的实验中进行了应用和研究。在原子核能级寿命测量实验中成功利用快定时法测量了能级寿命,获得的结果与NNDC发布的评估寿命相符合。在束粒子鉴别实验中对不同能量的质子束,α,12C束以及28Si产生的次级束粒子进行了测量,可以对不同的粒子进行鉴别。本文对DRS4数字化波形采样系统以及数字化波形分析算法进行了多种应用研究。实验结果表明DRS4系统以及数字化波形分析算法在能量和时间测量上相比传统的CAMAC系统具有更高的测量精度。同时该系统还具有通道密度高、电路简单,集成度高、体积小、传输噪声小、成本低、易调试以及信息集总分析的优点,满足了我们对TOF-PET读出电子学的设计需求。
[Abstract]:Positron Emission tomography (PET) can monitor the dose distribution and location of heavy ion beam irradiation. The introduction of time of flight time into PET can reduce the data processing time and improve the image quality.In the development of TOF-PET system for heavy ion cancer monitoring, the traditional discrete electronic readout system can not meet the needs of TOF-PET system because of its large scale, complex circuit, high power consumption, low measurement accuracy and poor reliability.Therefore, it is necessary to design and develop a new low-cost, high-integrated readout electronics system.Based on this requirement, we have developed a digital waveform sampling system based on SCA(Switched Capacitor Array-based DRS4 chip Dumino Ring Sampler version 4, which can sample 16 signals simultaneously in cascade mode.It has the function of On-Board conformance measurement, and can realize the measurement of TOF information and energy.In this paper, the output pulse of TOF-PET timing calibration system based on LaBr3 crystal is sampled by digital waveform sampling and data acquisition. The application of digital waveform sampling system based on DRS4 chip and the research of subsequent data processing method are carried out.The experimental results show that,Using DRS4 system and TOF-PET timing calibration system, good coincidence time resolution (178pss) and energy resolution (3.4222r 511keV) are obtained, which is better than that obtained from CAMAC system (250pss) and energy resolution (4.2keV).A TOF-PET cell prototype composed of a LaBr3 crystal array, a position sensitive photomultiplier tube and a simplified readout circuit has been successfully developed.For the first time, the DRS4 system is used to test the On-Board conformance of the prototype in China, and the digital algorithm is used to analyze the sampling data.Compared with CAMAC system, the crystal position map obtained by using DRS4 system is clearer and easier to partition.The higher SNR. DRS4 system obtained better energy resolution (14.9) position resolution (0.74mm) and coincidence time resolution (750psN). The feasibility of the application of DRS4 system in TOF-PET was verified and the expected goal was achieved.We have used DRS4 system for the first time in the measurement of nuclear energy level lifetime and in the experiments of beam particle identification.In the experiment of nuclear energy level life measurement, the fast timing method is successfully used to measure the energy level lifetime. The obtained results are in agreement with the estimated lifetime released by NNDC.In the beam particle identification experiment, the proton beam with different energy, the 伪 ~ (12) C beam and the secondary beam produced by 28Si were measured, which can be used to identify different particles.In this paper, DRS4 digital waveform sampling system and digital waveform analysis algorithm are studied.The experimental results show that the DRS4 system and the digital waveform analysis algorithm have higher measurement accuracy than the traditional CAMAC system in energy and time measurement.At the same time, the system has the advantages of high channel density, simple circuit, high integration, small volume, low transmission noise, low cost, easy debugging and information lumped analysis, which meets the design requirements of TOF-PET readout electronics.
【学位授予单位】：中国科学院研究生院(近代物理研究所)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O571.6

【参考文献】