SCI Rings, Switches, and Networks for Data Acquisition Systems

Abstract

In plasma-physical fusion devices, the ionized hydrogen isotopes Deuterium and Tritium are fusing to helium ions, provided that they can be kept long enough and dense enough at very high temperatures (typically ≫ 1 million degrees), thereby delivering energy according to the equation $E = (m_{Deuterium/Tritium}-m_{Helium})~ \times ~c^{2}$. To control the plasma confinement and to get information about its physical behavior, a high-speed and high-volume data acquisition system is needed for the on-line and off-line monitoring and evaluation of measured plasma and fusion device data. State-of-the-art experiments produce approx. 100 MByte of measurement values during a 10 second experimental period. Future plasma devices will deliver one to two orders of magnitude more data in the same time interval, while additionally operating continuously in a steady-state mode. This imposes high requirements on the real-time behavior, i.e., the transmission latency, as well as on the bandwidth of the underlying communication network that is part of the data acquisition system. A low and guaranteed latency is very important for the closed-loop feedback systems of the fusion device that keep the burning plasma hot, stable, and away from physical material.

Partially reprinted from: H. Richter and M. Ohlenroth: Data acquisition with the SCINET, a scalable-coherent-interface network, Fusion Engineering and Design, vol. 43, pp. 393-400, Copyright 1999, with permission from Elsevier Science