Development Of Data Acquisition System For CATCH Pathfinder

The Chasing All Transients Constellation Hunters(CATCH)mission is a largescale astronomical observation constellation proposed by Institute of High Energy Physics,Chinese Academy of sciences,aimed at exploring the dynamic universe through the fast follow-up observations of transient sources.The first pathfinder of CATCH will test the key technologies of the constellation,and the Silicon Drift Detector(SDD)system is one of the key scientific payloads.In order to solve the data acquisition problem of satellite payload in orbit,this paper completes the development of a prototype data acquisition system for the SDD detector array of the first CATCH test star based on Field Programmable Gate Array(FPGA for short),which adopts an innovative four-channel integrated module to realize multi-channel data parallel acquisition.By using the proposed sequencing algorithm the reception and storage of multiple types of events are successfully realized.In addition,the numerical filtering algorithms are used to optimize input data,greatly improving the system’s anti-noise performance and conversion linearity.The experimental results show that the data acquisition system has excellent signal processing capabilities,especially with an outstanding dynamic response speed.In order to correctly acquire astronomical signals,the SDD detection system is composed of two main circuit modules,i.e.,the front-end circuit and the back-end circuit,and the back-end circuit is the data acquisition system.In order to better realize the detection system’s data acquisition capability,it is necessary to focus on the analysis of main components of the front-end circuit,and study the working principle and characteristics of the SDD based on the working mechanism of semiconductor devices.The charge-sensitive amplifier is an important charge multiplier,which can improve the original weak pulse signal.With the circuit analysis methods,the amplification factor and performance parameters of the charge-sensitive preamplifier were successfully derived,which can provide a basic model for the subsequent analysis and optimization of the detector system’s performance.The filtering shaping circuit is used to improve signal quality and reduce the probability of signal pile-up under high count rate,thereby improving the system’s dynamic response capability.The fieldprogrammable gate array is a powerful and flexible semi-custom logic device,and the data acquisition system was successfully developed based on the hardware-software co-development method.The data acquisition system consists of a local clock module(time Cnt),an event generation module(sample),a storage module(ram),and a data transmission module(lvds＿tx).The modules and test files are written in hardware description language(VHDL),and the module development is based on a top-down design thinking,while the innovative use of counters for process and state machine control greatly improves the system development efficiency.The China Seismo-Electromagnetic Satellite(CSES),which has similar orbital conditions to CATCH,is also equipped with an SDD detector system.By analyzing the original detection data of CSES,the first study on the energy calibration of CSES in orbit and the evolution of SDD energy resolution at long time scale is completed.Based on the evolution of the energy resolution of the SDD detector of the satellite,it is projected that the energy resolution of the SDD can still meet the requirements after the CATCH test star has been in orbit for 3 years.This provides an important reference for the development of the detector system hardware,and is also an important scientific achievement of CSES.