Thomson Scattering Diagnostics on MAST

Thomson scattering on MAST is a European wide collaboration involving UKAEA and, at present, FOM (Netherlands), University College Cork (Ireland), and Aarhus university (Denmark). This diagnostic plays a key role in developing the scientific basis for fusion energy production with measurements providing the link between theory and experiment

A dual Thomson scattering system is implemented in MAST for measuring the plasma electron temperature and density. The layout is shown below.

The complementary features of each approach are exploited. One system, giving very high (300 point) spatial resolution, shows the detailed profile behaviour across the plasma, as shown in Fig 2.

Fig 2: electron temperature and density profiles from the 300 point ruby laser Thomson Scattering system showing full diameter profile measurements.

The other system uses a series of Nd YAG lasers each pulsing at 50Hz (every 20ms) to provide detail of the profile evolution in time. At present scattering is detected from 19 points using 4 lasers.

Fig 3 Surface plot of electron temperature data at 100 Hz from a two-laser Nd:YAG system. The effect of sawteeth and other MHD events can be seen in the time development of the discharge.

The TS Team (L to R): M. J. Forrest, M. R. Dunstan, R. O’Gorman, M. J. Walsh, S. K. Neilsen, P. G. Carolan, E. R. Arends (inset).

January 2003

Back to MAST home page