Preliminary implementation of the real-time data sharing system based on RFM for EAST

Abstract

For EAST experiments, the plasma control system (PCS) needs a lot of diagnostic data produced by the distributed subsystems of EAST to meet the requirements of steady-state plasma control. But due to the factors of different sampling frequencies of the subsystems and the signal distortion caused by long distance transmission, it’s difficult for the PCS alone to acquire all the diagnostic data in each control cycle. So the real-time data sharing system is designed to solve the problem of real-time data transmission between the PCS and the subsystems so as to realize data sharing among the distributed EAST systems.In consideration of the required transfer speed and data volume, a “multiple networks” structure composed of a reflective memory (RFM) network and a Gigabit Ethernet network is used to build this system. To work with this multi-network structure, Red Hat MRG Realtime (Messaging, RealTime, and Grid) operating system (OS) is adopted, as it can provide deterministic response time. This system is responsible for transferring the diagnostic data collected by the data acquisition (DAQ) systems of the various distributed subsystems to the PCS and data server. The PCS receives the data through the RFM network in each PCS control cycle (defined as 100 microseconds) while the data server receives the data through the Ethernet network in every time-slice (defined in the DAQ program). All the relevant diagnostic data are to be available to the PCS through the data sharing system, though the PCS has the ability to choose some specified data according to its own needs during the plasma control. Likely, the above advantages for the PCS also apply for any EAST subsystems connected to the RFM network. In this paper, the details of the real-time data sharing system are described and the future work is also discussed.