Real-time signal communication between diagnostic and control in ASDEX Upgrade

The ASDEX Upgrade tokamak experiment is equipped with a versatile discharge monitoring and control system. It allows to develop and use advanced control algorithms to investigate plasma physics under well-defined conditions with the objective of optimising plasma performance. The achievable quality depends on the accuracy with which the plasma state can be reconstructed from measurements under real-time conditions. Today's advanced algorithms need physics quantities - scalar entities as well as profiles. These are obtained processing huge numbers of raw measurements with complex diagnostic algorithms. Adequate network communication for the resulting signals is crucial to satisfy real-time requirements, especially when several diagnostic systems cooperate in a feedback control loop. Support for the technology of choice, however, is not easily available for all of the diverse, highly specialised diagnostic systems. We give an overview about the methods that have been explored at ASDEX Upgrade for real-time signal transfer. In particular, we investigated reflective shared memory and Ethernet technologies. Our solution strives to combine their strengths. For fast communication on dedicated computing nodes, reflective shared memory is used. For the majority of diagnostic systems producing large data blocks at moderate rates, Ethernet connections with UDP protocol are employed. Following ASDEX Upgrade's framework concept, a software layer hides the networks used from both diagnostic and control applications. (C) 2010 Elsevier B.V. All rights reserved.