Clock distribution for BaF2 readout electronics at CSNS-WNS  

作　　者：何兵 曹平 张德良 王奇 张雅希 齐心成 安琪 

机构地区：[1]State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei 230026, China [2]School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026, China [3]Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China

出　　处：《Chinese Physics C》2017年第1期162-166,共5页中国物理C（英文版）

基　　金：Supported by National Research and Development plan(2016 YFA0401602);NSAF(U1530111);National Natural Science Foundation of China(11005107)

摘　　要：A BaF2（Barium Fluoride） detector array is designed to precisely measure the（n, γ） cross section at the CSNS-WNS（white neutron source at China Spallation Neutron Source）. It is a 4π solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from the BaF2 detector, a pulse shape discrimination method is used, supported by a waveform digitization technique. There are 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, a clock prototype for the BaF2 readout electronics at CSNS-WNS is introduced. It is based on the PXIe platform and has a twin-stage tree topology. In the first stage, clock is synchronously distributed from the tree root to each PXIe crate through a coaxial cable over a long distance, while in the second stage, the clock is further distributed to each electronic module through a PXIe dedicated differential star bus. With the help of this topology, each tree node can fan out up to 20 clocks with 3U size. Test results show the clock jitter is less than 20 ps, which meets the requirements of the BaF2 readout electronics. Besides, this clock system has the advantages of high density, simplicity, scalability and cost saving, so it can be useful for other clock distribution applications.A BaF2（Barium Fluoride） detector array is designed to precisely measure the（n, γ） cross section at the CSNS-WNS（white neutron source at China Spallation Neutron Source）. It is a 4π solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from the BaF2 detector, a pulse shape discrimination method is used, supported by a waveform digitization technique. There are 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, a clock prototype for the BaF2 readout electronics at CSNS-WNS is introduced. It is based on the PXIe platform and has a twin-stage tree topology. In the first stage, clock is synchronously distributed from the tree root to each PXIe crate through a coaxial cable over a long distance, while in the second stage, the clock is further distributed to each electronic module through a PXIe dedicated differential star bus. With the help of this topology, each tree node can fan out up to 20 clocks with 3U size. Test results show the clock jitter is less than 20 ps, which meets the requirements of the BaF2 readout electronics. Besides, this clock system has the advantages of high density, simplicity, scalability and cost saving, so it can be useful for other clock distribution applications.

关 键 词：CSNS-WNS BaF2 detector array clock system PXIe readout electronics 

分 类 号：O571.53[理学—粒子物理与原子核物理]