Using the network as bus system for long discharge data acquisition and data processing

Data acquisition in shot-based fusion experiments is characterized by a large amount of data collected within a short time. The stellarator experiment Wendelstein 7-X (W7-X) will produce a considerable higher amount of data in a continuous and steady-state operation within half an hour. Therefore, it is not sufficient to wait until all data has been acquired and stored in the database before being able to view and analyze data. Continuous and robust data transport is needed for (1) a distributed data monitoring system to visualize trends, (2) continuous data acquisition of data available at the network and (3) message signaling.The paper introduces a network channel concept covering a system-wide available data description, half sync/half async communication pattern, data serialization, identification and matching of data. It is focusing on the IP Multicast/UDP implementation for the data monitoring system and presents results of performance measurements. Suitability and limitations are discussed and an appropriate answer to the question “When is IP Multicast/UDP reliable?” is given.