Digital Trigger Method For Back-n At China Spallation Neutron Source

Nuclear data is the collective name for nuclear reaction data and nuclear structure data.The nuclear reaction data is used to describe the nature of the interaction between the incident particle and the nuclear,and the nuclear structure data is used to describe the basic properties of a single nuclear nuclide.Nuclear data is the most basic data for all research and applications related to atomic nuclei.Neutron nuclear data is an important part of nuclear data.It plays an important role in nuclear energy development,nuclear waste treatment,nuclear medicine,national defense construction,and nuclear physics research.The measurement of nuclear data in China began in the 1960s.After several decades of development,China has established the CENDL,which serves the development of Chinese nuclear industry and has the ability to carry out experimental measurement,theoretical simulation and evaluation.With the development of the national economy,the application of nuclear data is expanding.New reactors,controlled nuclear fusion,nuclear medicine,fundamental physics research and space exploration have put forward new requirements for nuclear data accuracy,nuclide types and energy regions.In order to promote the development of our country in the field of nuclear data and meet the requirements for the measurement of nuclear data in the new period,Back-streaming neutrons through the incoming proton channel at the target station of China Spallation Neutron Source(CSNS)has been exploited as a white neutron beam line(so-called Back-n),which is dedicated to nuclear data measurement.In order to meet the diverse requirements of nuclear data measurement,a variety of spectrometers have been planned on Back-n.Each spectrometer has a different physical target and therefore requires different readout electronics.To meet the requirements of refined measurement of nuclear data,and to simplify the development of readout electronics,this paper proposes a general method that is highly scalable and flexible and can be applied to most spectrometers at Back-n.In this soluation,the analog conditioning circuit and the digitization circuit are separately designed.The output signal of each detector is modulated by a dedicated signal conditioning module,and then digitized by a shared high-speed,high-precision waveform digitalization module.In the existing nuclear data measurement experiments using waveform digitization method,readout electronics usually use traditional analog hardware trigger method or full software trigger method.The traditional analog hardware trigger method has a large dead time and the event rate that can be dealt with is low.And the software trigger method has to deal with massive amounts of data,and the cost of data transmission and processing is high.This paper studies the high speed and precision readout electronics which is adaptable to the diversified spectrometers at Back-n.Based on the acquired full-waveform data,the general-purpose readout electronics fully utilize the real-time,flexibility and parallel processing capability of FPGA to extract the waveform information,and use the rich backplane resources of the PXIe platform and high speed serial communication technology to build a flexible and reconfigurable multi-level fully digital trigger system,to solve the problem of data acquisition,transmission and processing efficiency caused by muti-channel high speed and high precision sampling,improving the accuracy of nuclear data measurement and improving trigger rate of the system.In addition,this paper explores the application of machine learning method to the digital trigger system,and demonstrates the feasibility of the method.