Data structures for the description of tokamak diagnostics

The data acquisition system for the ASDEX-upgrade experiment is a distributed system, consisting of about 30 autonomous diagnostic subsystems (ADS), typically a micro VAX or similar running with UNIX, a central data analysis system (CDAS), on an IBM 4381 main frame with one CPU and at least 16 Mytes of memory, and a fiber glass connection network, permitting a transfer rate of at least 100 Kytes/sec from each ADS, and a total through-put of at least l Mytes/sec. The author reports on an open-ended file structure designed to describe shot-files. For each entity, like a CAMAC device, the diagnostic descriptor, a signal or a signal group, a time base, etc., an object descriptor exists in the file that permits the automatic collection of CAMAC data by an ACQUIRE task: a list of these objects, together with a mapping function, specifies how signals are constructed from the contents of CAMAC memories. The shot file thus constructed for each diagnostic on its ADS is sent to the CDAS where all data are spread out in memory. The shot file structure is complemented with a set of access procedures (usable by FORTRAN77 programs) that permit access to a shotfile (also older ones), to individual diagnostics of it, and their signals by using the appropriate symbolic names