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中国物理学会期刊

高精度数字化定时方法研究

Study on High-Precision Digital Timing Methods

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  • 随着核物理与核探测技术的发展,传统模拟电子学获取系统难以满足大规模探测阵列的需求。数字化获取系统凭借其低单通道成本、小死时间及参数灵活可调等优势,正得到日益广泛的应用。然而,高精度时间测量仍是其关键技术瓶颈,尤其在测量寿命短于采样时间间隔时,需依赖插值算法重建采样点间的信号,其精度易受相位差、采样率、波形形状、定时方法及插值参数等因素制约。本文通过模拟仿真,系统研究了数字化恒比定时方法在不同参数下的精度变化。结果清晰地揭示了相位差对定时精度的显著影响,并证实提高采样率可有效抑制该影响。研究发现,为实现最优定时精度,输入信号的上升沿时间并非越短越好,而是存在一个最佳区间。通过采用统一的恒比定时方法处理不同上升沿速率的信号,发现在不同采样率下,当上升沿涵盖4至6个采样点时,可获得最佳的定时精度。本研究对数字化快时间测量系统的优化设计具有指导意义。

     

    With the development of nuclear physics and detection technology, traditional analog data-acquisition (ADAQ) systems struggle to meet the demands of large-scale detection arrays. At the same time, digital data-acquisition (DDAQ) is widely employed due to the low per-channel cost, small dead time, and flexible parameter setting. However, high-precision time measurements remain a critical technical bottleneck for DDAQ, particularly when the desired resolution is smaller than the time interval between neighboring samples. Interpolated algorithms between adjacent samples must be used in order to get a better timing resolution. However, such Interpolated time information is significantly affected by the phase of signal, sampling rate, intrinsic pulse shape, discrimination parameters, and so on. The current work aims at quantifying the impacts of each aforementioned parameters on the timing precision in DDAQ. In this simulation work, the pulses are generated with different parameters, digitalized by an adjustable sampling rate, and then processed by a Digital Constant-Fraction discrimination (DCFD) algorithm. By modifying different parameters such as signal phase, pulse shape, and discrimination parameters, their impacts on timing precision have been investigated. The results conclusively confirm the strong influence of signal phase on the time accuracy in DDAQ. On the other side, if one wants the best time resolution, the rising time of nuclear pulses can neither be too short nor too long, namely, with 4–6 samples on the leading edge would be the best choice.

     

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