Y. T. Zhang

Clock distribution for BaF2 readout electronics at CSNS-WNS*

aF2 (Barium Fluoride) detector array is designed for the measurement of (n,{\gamma}) cross section precisely at CSNS-WNS (white neutron source at China Spallation Neutron Source). It is a 4{\pi}solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from BaF2 detector, pulse shape discrimination methodology is used, which is supported by waveform digitization technique. There are total 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, the clock prototype for BaF2 readout electronics at CSNS-WNS is introduced. It is based on PXIe platform and has a twin-stage tree topology. In the first stage, clock is distributed from the tree root to each PXIe crate synchronously through coaxial cable over long distance, while in the second stage, clock is further distributed to each electronic module through 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 result shows the clock jitter is less than 20ps, which can meet the requirement of BaF2 readout electronics. Besides, this clock system has advantages of high density, simplicity, scalability and cost saving, which makes it can be used in other applications of clock distributing preciously.

System design for precise digitization and readout of the CSNS-WNS BaF 2 spectrometer

The BaF2 (barium fluoride) spectrometer is one of the experiment facilities at the CSNS-WNS (White Neutron Source at China Spallation Neutron Source), currently under construction. It is designed to precisely measure the (n, γ) cross section, with 92 crystal elements and complete 4π steradian coverage. In order to improve the precision of measurement, in this paper, a new precise digitization and readout method is proposed. Waveform digitizing with 1 GSps sampling rate and 12-bit resolution is used to precisely capture the detector signal. To solve the problem of massive data readout and processing, the readout electronics is designed as a distributed architecture with 4 PXIe crates. The digitized signal is concentrated to the PXIe crate controller through a PCIe bus on the backplane and transmitted to the data acquisition system over gigabit Ethernet in parallel. Besides, the clock and trigger can be fanned out synchronously to every electronic channel over a high-precision distribution network. Test results show that the prototype of the readout electronics can achieve good performance and meet the requirements of the CSNS-WNS BaF2 spectrometer.

Evaluation Software for BaF 2 Detector Array Electronics at CSNS–WNS

The “in programming barium fluoride (BaF2) detector array” is one of the experiment facilities at China Spallation Neutron Source-White Neutron Sources, which is designed for the measurement of neutron capture cross section with high accuracy. It consists of 92 crystal elements with completely

Proposal of Readout Electronics for CSNS-WNS BaF2 Detector

4\pi

Prototype of Field Waveform Digitizer for BaF 2 Detector Array at CSNS-WNS

solid-angle coverage, which needs 92 analog channels and 92 digitization channels for data acquisition. Accordingly, the readout electronics is comprised with four distributed readout PXIe crates, containing 46 field digitization modules (FDMs). Each FDM supports two valid channels for signal digitizing. In this paper, evaluation software is designed for evaluating the performance of BaF2 readout electronics. It focuses on evaluating the performance of data transmission, waveform digitizing, and working status monitoring. Test results show that the evaluation software can correctly acquire and assemble data from the BaF2 readout system and evaluate the analog digital converter (ADC) performance under ADC test mode. FDMs in the readout system can also be monitored and controlled by this software in real time.