Research And Design Of The Data Transmission Prototype System For The External Target Experiment In CSR

As a new branch of nuclear physics, the heavy ion physics is developing rapidly. At present, a variety of heavy ion accelerators have been built or is under construction.in the world. And the Cooling Storage Ring of Heavy Ion Research Facility at Lanzhou (HIRFL-CSR) which was designed and built by China has reached the international advanced level.The external target facility (ETF) is an experimental site of the HIRFL-CSR which located between the main ring (CSRm) and the experimental ring (CSRe). With various types of detectors such as start time detector, y detector, Multi-Wire Drift Chambers (MWDC), Time of Flight (TOF) wall and neutron wall, the ETF can be used for studies on nuclear matter, radioactive ion beam physics, hypernuclei, etc. This thesis will introduce the data transmission prototype system designed for the ETF.By introducing ideas including stream computing and computing method based on key-value pairs from the area of big data processing, a stream-based data transmission system is designed. With a network formed by stream processing nodes, the system can accomplish tasks such as reading out data from front-end electronics, transmission and event building. The scalable system supports user to adjust the stream processing network topology freely and can achieve parallel processing and load balancing flexibly. Besides, the system can fit various requirements related to data acquisition by defining standard interface for different types of detectors and allowing user to add custom logic nodes conveniently.The structure of this thesis is organized as below:The first chapter is an introduction, which mainly introduces the objectives and structure of the ETF, as well as the requirements for data acquisition (DAQ) system.The second chapter introduces some typical DAQ systems for large-scale physics experiment in the world and some new techniques in area of big data processing. This systems and techniques are important references during the design of the data transmission system for the ETF.In the third chapter, combined with research results in the second chapter and the specific needs of the ETF, the framework and work flow of the designed stream-based transmission system is described. The architecture of the system can be divided into two part. One is the network formed by logic nodes for core tasks like data transmission and processing. And another is the subsystem for monitoring and control the status of the whole DAQ system.The fourth chapter gives more details on the implementation of the system, because these details directly affect the system performance. Unified specifications for designing logic nodes are raised. And through the design of a global buffer data structure, demands of moving data among logic nodes are effectively reduced.The fifth chapter is about the test result of the system. On the one hand, performance of logic nodes which are implemented via software is evaluated. On the other hand, tests are applied together with front-end electronics and detectors to verify the reliability of the system and whether the system meets the requirements of the ETF.The sixth chapter summarizes the content of this thesis and points out the direction of further research.