Evolution not revolution in the TCV tokamak control and acquisition system

The original TCV control system was designed in the late 1980s to be inherently network based in that all control operations were performed from X-windows terminals and the control computers were networked. Using VMS–VAX technology, the acquisition system (CAMAC) and control system (BITBUS) were connected to controllers situated in the machine bus of these machines that were linked homogeneously by the VMS ‘cluster’ technology. Although the computing power and network bandwidth have improved considerably over the last years, the data acquired has risen from ∼10 to ∼200 MB per plasma discharge from increasingly numerous and complex diagnostic and acquisition systems. The goal over this period has thus been to evolve the control and acquisition systems to embrace new technologies whilst retaining the remote and automatic features. This paper describes changes in both the hardware and software which leave TCV in a state whose structure is coherent with its origins yet includes many new components. To control this increased complexity, a very general and symmetric software paradigm was developed based on an efficient matrix capable interpreter that is part of the MdsPlus (Proc. 16th Symp. Fus. Tecnol. (1990) 1272) package. This Tree Data Interface (TDI) package has many of the Matlab/IDL capabilities together with the explicit capability of calling dynamic libraries directly. There is also a TDI TCP/IP server for a remote client to call these functions and obtain a reply. With the recent port of MdsPlus to many Unix flavours, WinXX and VMS, which features automatic machine binary format translation, communication between most computers at TCV can be performed over the same interface. By writing all the CAMAC, BITBUS and database handling routines in this language, all the TCV functionality is now symmetrically available across all platforms. Client interfaces from C, Fortran, MatLab, IDL, Java, etc. are available for execution of TDI functions on local and remote machines. By ensuring that new control or computing hardware is supplied with this interface, it is possible to not only control all TCV functions from our central computers, but to further evolve the system by exporting some or all control to another computer with different architecture whilst retaining the same TDI routines.