一种用于快定时探测器的瞬态波形采样技术的研究

A Front-End Electronics(FEE) based on waveform sampling is one of the popular trends in the prospective particle physics experiment. However, the waveform sampling technology based on Flash ADC(FADC) could not be widely used in practical application as the limtaions of low channel densities, huge power comsuption, as well as high financial burden. An alternative to FADC is the usage of switched capacitor arrays(SCA). Detector signals are sampled and stored in a series of capacitors. These capacitors are then read out and digitized externally with an ADC at a lower rate. Nowadays, many experiments require the highest resolution together with large numbers of channels in the data acquisition system at a lower cost. Therefore, a study of waveform sampling technology based on switched capacitor arrays will be implemented. Some key technologys, such as waveform digitizing, algorithms of charge pickoff, timing techniques, high speed data transfer, etc., will be explored in this project. A 14bit 5GSPS transient waveform sampling system will be designed. The waveform sampling technology is mainly applied to the nuclear physics experiment for time distribution measurement of related events. Meanwhile, the technology also can be used in the researches of the particle physics, nuclear astrophysics and nuclear medicine.

波形采样技术是未来粒子物理实验前端电子学发展的主要趋势之一。基于FADC（Flash ADC）的波形采样不仅集成度低、成本高，而且随着采样率和通道数的提高，功耗越来越大，使得该技术在实际应用中受到了很多限制。新兴的基于开关电容阵列的波形采样技术采用高速模拟采样+慢速高精度ADC变换的路线，可同时实现高速、高精度的瞬态波形采样。本课题拟开展基于开关电容阵列的瞬态波形采样技术研究，探索高速波形采样实现方法、电荷提取算法、波形定时技术、高速数据传输等技术与电路。研发14bit 5GSPS的瞬态波形采样测量系统，并通过在FPGA内编程实现定时算法，以满足快定时探测器高分辨、多参数、多通道、低功耗的需求。 本项目研究结果主要应用于核物理实验中测量时间相关事件的时间分布，提高时间测量的精度。该技术的实现也可以应用于粒子物理，核天体物理及核医学等研究领域。

波形采样技术可通过一种硬件所获得的波形数据经过不同算法处理得到多种物理参数，大大减少了硬件种类，提高了线路的灵活性。该技术在未来粒子物理实验、核天体物理及核医学等领域有极其诱人的前景。基于快定时探测器高分辨、多参数、多通道、低功耗的需求，本项目成功研制了瞬态波形采样测量系统，整个电子学系统只由波形数字化电路板及读出控制上位机软件组成。该系统信号输入动态范围约1Vpp，随机噪声水平好于0.5mV，采样率700MHz~5GHz，信号输入带宽~800MHz，并可以通过电路板间级联实现通道数的扩展。开展了波形采样数据的电荷提取算法、定时技术的研究，并结合探测器进行了联合测试。最终将该系统应用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，C-12束以及Si-28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。