Real time operation of MAST Thomson scattering diagnostic

Abstract

The MAST (Mega-Amp Spherical Tokamak) TS (Thomson scattering) diagnostic provides measurements of electron temperature and density at 130 spatial points with ~10 mm resolution across the plasma. Eight 30 Hz 1.6 J Nd:YAG lasers have been combined to produce an average sampling rate of 240 Hz with minimum interval >; 1 μs. The scattered light signals are registered as polychromator outputs at 1 GHz rate in a short interval around each laser pulse. There are two tasks when real-time system capability is needed: 1) triggering of lasers and acquisition on plasma events to provide higher time resolution; 2) output physical data, electron temperature and density, in real-time for plasma control and other applications. In a standard mode the system works with post-shot data acquisition; the physical data are produced as a result of intensive processing including results from other diagnostics. The real-time mode requires a fast processing algorithm and a fast way for gathering and dispatching data. This paper presents the implementation of real-time capabilities and first results of their usage.