Real-time plasma control at JET using an ATM network

The joint European Tokamak (JET) contains a toroidal plasma at near-breakev en conditions for several seconds. The Plasma Shape Control System (PPCC-SC ) drives poloidal field coils. It determines the plasma boundary using the XLOC algorithm and data from the Magnetics Measurement System, KC1D. The ad ditional heating systems, NE (Neutral Beam), ICRH (lon Cyclotron Resonance Heating), and ECRH (Electron Cyclotron Resonance Heating) can be controlled by real-time algorithms on the RTSS (Real-Time Signal Server). The Wall Lo ad Limit System limits the power applied to the vessel. Also, experimental systems analyze data in realtime, e.g. RT-BETA-LI calculates Wdia Beta, Li, etc., and RT-EFIT calculates the current profiles and flux-surfaces. These systems are hosted on a variety of hardware/software platforms, including - VME/VxWorks, TMS320C40 DSP/native code, and PC/WindowsNT. They communicat e using ethernet, fibre-optic point-to-point links, or with reflective memo ry. To improve reliability and flexibility, a new real-time data network (R TDN) is being developed, using standard ATM components. Simple tests on ATM connections indicate that, for packets of a few hundred bytes, point-to-po int transfers take less then 250 mu s, which is adequate. ATM links for the DSP systems have been developed, based on a PowerPC VME card. A simple mes sage protocol, application programmer interface, and data presentation tool s have also been developed.