National Spherical Torus Experiment Real Time Plasma Control Data Acquisition Hardware
Authors: R.J. Marsala and J. Schneider
Date of PPPL Report: August 2002
Prepared for: the 22nd Symposium on Fusion Technology to be held in Helsinki, Finland, September 9-13, 2002. Symposium papers will be published in a special issue of the journal Fusion Engineering and Design.
The National Spherical Torus Experiment (NSTX) is currently providing researchers data on low aspect-ratio toroidal plasmas. NSTX's Plasma Control System adjusts the firing angles of thyristor rectifier power supplies, in real time, to control plasma position, shape and density. A Data Acquisition system comprised of off-the-shelf and custom hardware provides the magnetic diagnostics data required in calculating firing angles. This VERSAmodule Eurocard (VME) bus-based system utilizes Front Panel Data Port (FPDP) for high-speed data transfer. Data coming from physically different locations is referenced to several different ground potentials necessitating the need for a custom FPDP multiplexer. This paper discusses the data acquisition system configuration, the in-house designed 4-to-1 FPDP Input Multiplexing Module (FIMM), and future expansion plans.