The Use of MDSplus on NSTX at PPPL

The MDSplus data acquisition system has been used successfully since the 1999 startup of the National Spherical Torus Experiment (NSTX) for control, data acquisition and analysis for diagnostic subsystems. Prior to first plasma on NSTX, software engineers collectively spent 1 man-year to learn the system and bring it to operation, and 4 full-time equivalents continue to support its uses. The 30 primary, on-site physicists and 25 part-time physicists adapted to the MDSplus software tools with no real difficulty. After a few uses, most users valued the features and usability of Scope and Traverser, the most commonly used MDSplus components. Within 3 minutes of the 1-second plasma “shot” on NSTX, 40 MBs are acquired from CAMAC crates on a VMS system, 22 MBs from UNIX systems, and 13 MBs from PC systems, and loaded into MDSplus hierarchical data structures, called trees. Local users and remote collaborators alike configure their X-windows to display dozens of plots, as data becomes available. Data can be read from MDSplus trees into high-level language codes at 500 KB/s on our VMS systems, and about 20% slower on our Unix systems. All NSTX data stored in MDSplus is always on-line from VMS-served RAID disks. Information is written directly from PC-based “turn-key” systems into MDSplus, using routines called from C++, LabView, Visual Basic and IDL. Several legacy FORTRAN analysis codes have been converted to use MDSplus with minimal effort. Experiment-specific tools and routines in our user-written IDL libraries have been layered on top of MDSplus. Database tools are being converted from INGRES to MS-SQL. Web-based plotting, tree-searching, and database tools have also been developed and various parts of MDSplus have been documented on the web. Many of these tools should be useful to other MDSplus sites. The support from the developers at MIT, especially with the intricacies of the TCL and TDI languages, was timely and insightful. The use of MDSplus has resulted in both a better system and a significant cost savings for NSTX.